SUBMARINE REPORT

DEPTH CHARGE, BOMB, MINE, TORPEDO

AND GUNFIRE DAMAGE

INCLUDING LOSSES IN ACTION

7 DECEMBER, 1941 TO 15 AUGUST, 1945

VOLUME I and VOLUME II

(For reference purposes, VOLUME II begins on page 161.)

Preliminary Design Branch
Bureau of Ships
Navy Department
1 January 1949

WAR DAMAGE REPORT No. 58

Printed By U. S. Hydrographic Office

SUBMARINE REPORT

Depth Charge, Bomb, Mine, Torpedo and Gunfire Damage

Including Losses in Action

7 December, 1941 to 15 August, 1945

1 January 1949

APPROVED



C. L. BRAND
Rear Admiral, USN
Ass't. Chief of Bureau for Ships

CONTENTS

SECTION

Page

I

FOREWORD

1

II

GENERAL

2

III

JAPANESE ANTI-SUBMARINE WARFARE AND WEAPONS

8

Name

No.

Damaged by

Locale

Date

IV

PERCH

176

Depth Charge

Java Sea

3/3/42

17

V

KINGFISH

234

Depth Charge

Formosa

3/23/43

26

VI

TUNNY

282

Depth Charge

Palau Is.

8/26/43

47

VII

SALMON

182

Depth Charge

S.E. of Kyushu

10/30/44

61

VIII

GRENADIER

210

Bomb

Malaya

4/22/43

82

IX

SCAMP

277

Bomb

Mindanao, P.I.

4/7/44

89

X

TANG

306

Torpedo

Formosa

10/24/44

109

XI

BERGALL

320

Mine

Gulf of Siam

6/13/45

125

XII

GRAMPUS

207

Gunfire

Truk

5/17/42

131

XIII

GROWLER

215

Collision

New Britain

2/7/43

137

XIV

DRAGONET

293

Grounding

Kurile Is.

12/15/44

148

XV

BEHAVIOR OF UNDERWATER NON-CONTACT EXPLOSIONS

161

XVI

HULL DAMAGE AND STRENGTH

177

XVII

STABILITY, BUOYANCY AND FLOODING

193

XVIII

SHOCK PROTECTION

203

XIX

ENGINEERING NOTES

213

XX

PIPING

223

XXI

233

XXII

SUBMARINE ESCAPE NOTES

239

XXIII

CONCLUSION

248

APPENDIX I

BRIEFS OF DAMAGE INCURRED BY U.S. SUBMARINES DURING WORLD WAR II.

250

APPENDIX II

TABULAR SUMMARY OF U.S. SUBMARINE LOSSES DURING WORLD WAR II.

296

APPENDIX III

MAP COVERING AREA OF PRINCIPAL U.S. SUBMARINE OPERATIONS.


SECTION I

FOREWORD

1-1. This report is one of a series of sixty-two war damage reports prepared by the Bureau covering damage received in action by vessels of the U.S. Navy during World War II. It is the only report of the entire series which deals with war damage sustained by submarines. The remaining sixty-one reports cover cases of significant damage incurred by surface vessels, and include many instances of torpedo damage which may be of interest to submarine personnel who desire information on the destructive effect of their principal World War II weapon, the torpedo.

1-2. As a group, U.S. submarines have established an enviable record in combat, not only in destruction inflicted upon the enemy but also in their ability to sustain severe attacks without themselves receiving serious damage. Although the basic operational characteristics of our submarines remained substantially unchanged throughout the war years, with the notable exception of considerably increased maximum allowable submergence depth for the SS285 and subsequent Classes, marked advances were achieved in practically every other aspect of submarine and submarine equipment design. Improvements in shock protection have resulted in submarines which are highly resistant to damage short of actual destruction of their pressure hulls.

1-3. It is the purpose of this report, by presenting case histories selected from the great volume of war experience, to illustrate the behavior of U.S. fleet type submarines in service during World War II when subjected to enemy attack, and in particular, to attack by non-contact underwater explosive charges since the Japanese anti-submarine forces employed the depth charge and bomb as their principal weapons. Cases of damage by mine, torpedo, gunfire and collision are also included. An effort has been made to present a comprehensive summation of the effectiveness with which our submarines withstood attack, the materiel and design weaknesses revealed by war damage, the damage control problems attendant upon flooding of intact spaces or derangement of vital systems and equipment, and the corrective measures taken to reduce the vulnerability of our submarines to damage. It is hoped that the information presented here will be of value to submarine operating personnel and submarine design, repair and outfitting activities.

1-4. No attempt has been made in this report to evaluate the operational and military characteristics of our submarines in the light of War experience other than by statements of fact when such characteristics were impaired through war damage, nor have casualties incident to. normal service operations been discussed. Lessons learned through the recent CROSSROADS OPERATION, and their possible effect on submarine design, have not been included.

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SECTION II

GENERAL

2-1. The evolution of submarine design in this country has been unlike that of other naval vessels in that the early development was carried forward by private citizens, rather than by the Navy Department. Although the HOLLAND, completed by the Holland Torpedo Boat Company in 1898, was commissioned as our first submarine in April 1900, and numerous submarines were purchased from private concerns and added to the fleet in subsequent years, it was not until 1914 that the construction of a submarine was undertaken by the government. This was the L-8, built at the Navy Yard, Portsmouth, N. H., to the design of the Lake Torpedo Boat Company. It was not until late in 1916 that a complete preliminary design was prepared by the Navy Department for a submarine, the S-3. Commencing with the same vessel, the Navy Yard, Portsmouth was entrusted for the first time with the development of the detailed working plans as well as the construction. From 1919 until 1931 all submarines ordered were built to plans prepared by Portsmouth. Thereafter, the Electric Boat Company has prepared the working plans for all submarines built by it, while the Navy Yard, Portsmouth has prepared working plans for practically all submarines built in government yards.

2-2. The fact that two design agencies have been engaged in the development of submarines has led, it is believed, to more rapid progress than would have been accomplished by either of these agencies alone. Although each of the design agencies is allowed considerable freedom in the development of the details of a design, control is maintained in the Navy Department by virtue of the fact that the preliminary designs are prepared in the Navy Department, the contract plans are prepared in the Department or by an agency of the Department, and all working plans are subject to its approval. Thus, the best features developed by either agency may be incorporated into the designs prepared by the other.

2-3. By the year 1902, practicable solutions for the basic problems of submarine design had been achieved, at least in principle: i.e., electric motor drive with storage battery power for submerged propulsion; internal combustion engines for surface propulsion; the self-propelled torpedo as a means of inflicting damage on the enemy; a crude periscope for taking surface observations while submerged; and a satisfactory means of obtaining submerged control through the use of hydroplanes and variable ballast tanks. Subsequent development has been in the direction of refinement of design of the submarine as a whole and of its component parts, improvement in military characteristics and changes in design to keep pace with changed conditions of employment, rather than in the direction of changes in basic principles. One major innovation was the change to double-hull construction to improve seaworthiness through increased reserve buoyancy. The M-1, completed in 1918, was the first submarine of this type.

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2-4. Commencing with the BARRACUDA Class of 1924 and continuing through the end of World War II, all submarines built by the U.S. Navy, with the exception of the 800 ton-type submarines MACKEREL (SS204) and MARLIN (SS205) completed in 1941, were of the fleet type, designed for high surface speeds and capable of operating for extended periods at sea and covering great distances. The submarine war effort of the United States was dependent almost entirely upon these fleet type submarines and for this reason only the damage experiences of fleet type submarines have been included in this report.

2-5. It is pertinent to mention that only negligible war experience was gained by our submarine service during World War I.1 The evolution of the fleet type submarine during the years of peace preceding World War II was the result of hypothesis and experience obtained through simulated exercises rather than actual war service conditions. The operating characteristics of the fleet type submarine proved adequate to carry the war to the enemy throughout the entire Pacific area, although great distances were involved.

2-6. U.S. submarine operations in the Atlantic during World War II were on a minor scale. Throughout the entire war only four enemy vessels were sunk by our submarines in the Atlantic, two of the four being German submarines, and but five other enemy vessels were damaged.2 Only one U.S. submarine was damaged in the Atlantic through enemy action.3 In the Pacific, however, where the major portion of our submarine effort was exerted, the U.S. submarine service established an impressive record almost from the first day of our entry into the war. Unrestricted submarine warfare against Japan was ordered by the Chief of Naval Operations on 7 December 1941. With the exception of a few special missions and support operations during the Battle of Midway and the initial phases of the Solomons Campaign, submarines were employed during the first two years of the war as free agents in a campaign of attrition against enemy combatant vessels and merchant shipping. With the inauguration of the Gilbert Islands campaign in November 1943, a gradually increasing percentage of the submarine effort was diverted to the support of fleet operations although normal offensive patrolling continued to the end of the war. The statistics of the Joint Army-Navy Assessment Committee credit U.S. submarines with the sinking of 54.6 percent of all Japanese naval and merchant vessel tonnage sunk during World War II by U.S. forces of all categories. The total of sinkings


1 So far as can be determined, the first vessel credited as destroyed by submarine action in the history of the U.S. Navy was the Japanese cargo ship ATSUTASAN MARU (8,662 gross tons), sunk in World War II by SWORDFISH (SS193) on 16 December 1941, lat. 18° -06N., long. 109° -44'E. (credited by the Joint Army-Navy Assessment Committee, NavExos Publication P-468).
2 Submarine Operational History, World War II, prepared by Commander Submarine Force, U.S. Pacific Fleet (Preliminary Issue).
3 BLACKFISH (SS221), damaged by German depth charge attack in the Bay of Biscay on 19 February 1943. See brief of damage in Appendix I.

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credited to U.S. submarines includes 201 Japanese naval vessels with a combined tonnage (standard displacement) of 540,192 tons, 29.6 percent of all Japanese naval tonnage sunk by U.S. forces, and 1113 merchant vessels above 500 gross tons with a combined tonnage (gross) of 4,779,902 tons, 60.4 percent of all Japanese merchant tonnage sunk by U.S. forces.1,2 The following numbers and types of combatant Japanese naval vessels were sunk by U.S. submarines: 1 battleship, 4 large aircraft carriers, 4 escort aircraft carriers, 3 heavy cruisers, 8 light cruisers, 38 destroyers, 23 submarines and 100 escort, patrol or mine vessels. In addition to the 1314 naval and merchant vessels credited as sunk, approximately 1000 Japanese vessels in all categories, with an estimated combined tonnage of over 5,000,000 tons, were damaged by U.S. submarines.3 It has been estimated that approximately 275,000 Japanese were killed as a direct result of Allied submarine operations.4

2-7. On 7 December 1941 there were 46 fleet type, 2 - 800 ton-type, 37 S-type, 18 R-type and 7 O-type submarines in commission in the U.S. Navy. Of these, 39 fleet type and 12 S-type were in the Pacific. On 15 August 1945, the day the war ended, there were 200 fleet type, 15 S-type, 10 R-type and 5 O-type submarines in commission. Of these, 169 fleet type and 13 S-type submarines were in the Pacific. A total of 202 fleet type submarines were completed and commissioned during the war.5

2-8. In all theatres during World War II, 269 U.S. submarines conducted a grand total of 1682 war patrols against the enemy. 251 submarines made patrols in the Pacific, of which 229 were fleet type boats and 22 were S-type boats. Of the total of 1682 war patrols, 948


1 Japanese Naval and Merchant Losses During World War II by All Causes, NavExos Publication P-468 of 3 February 1947, prepared by the Joint Army-Navy Assessment Committee. The figures of this committee are very conservative as compared with the official statistics of the various force commands.
2 ONI Statistical Section (Op-32F-44) data credits German submarines with the destruction of 2,321 naval and merchant vessels of the United Nations, for a grand total of 12,866,711 tons, during the period from September 1939 to the German surrender in May 1945.
3 Submarine Operational History, World War II, prepared by Commander Submarine Force, U.S. Pacific Fleet (Preliminary Issue).
4 Figure given by Japanese to the Administrator, U.S. Naval Shipping Control Authority for Japanese Merchant Marine. (Submarine Force Pacific Fleet Bulletin, Volume III, Number I of February 1946.)
5 During the period from September 1939 to their surrender in May 1945, the Germans built a total of 1100 submarines, divided into the following categories: 912 attack type submarines which became operational; 119 Type XXI attack submarines which were delivered by the final assembly yards but none of which became operational due to hydraulic system defects; 10 experimental submarines; and 59 submarines designed for special service such as minelayers, cargo carriers and submarine tenders. --NavTechMisEu Technical Report No. 312-45 of August 1945 entitled "German Submarine Design, 1935-1945."

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were conducted under the command of ComSubPac, 622 under the command of ComSubSoWesPac and 112 under the command of ComSubLant.

2-9. A survey of war patrol reports and other information available to the Bureau indicates that there were 110 separate instances, excluding losses, in which our fleet type submarines sustained damage from attack by either enemy or friendly forces where the damage received can be considered as more than negligible, or where the circumstances of the attack or the nature of the damage has been considered of sufficient interest to warrant mention. Brief accounts of each of the selected actions have been included in Appendix I of this report. The 110 cases of damage can be classified by cause as follows:

Cause

No. of Cases

Depth charge

58

Bomb

25

Depth charge and bomb

8

Aircraft strafing or small caliber gunfire

6

Medium caliber gunfire

4

Collision

4

Mass detonation of target ship

2

Mine

1

Kamikaze aircraft

1

Own torpedo

1

110

Of these 110 cases, about 15 can be classified as resulting in severe damage, about 50 as resulting in moderate damage, and the remaining 45 as resulting in only minor damage.

2-10. In 49 of the above 110 cases, the submarines were forced to terminate their patrols as a result of the war damage received. In many of these instances, the damage which caused the termination of a patrol was restricted to but one vital system or equipment and the sum of all other damage was only minor or even non-existent. For example, in TROUT's (SS202) action of 3 October 1942, only the periscopes were damaged but this casualty alone forced the ship to return to base for repairs. It is difficult in many of the cases where war damage forced termination of patrols to assign any one or two specific items of damage as being responsible. When damage was widespread, even though each item may in itself have been fairly minor or capable of being repaired by ship's force, the cumulative effect of the total was often sufficient to force the boat to return to base for repairs. A review of the 49 war patrols which were terminated due to war damage indicates that the following classification by cause can be made:

General severe damage

15

Widespread minor damage

4

Periscope damage (by explosion)

5

Periscope damage (by collision)

4

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Medium caliber gunfire damage

4

Leakage rendering depth control difficult

3

Reduction gear damage

3

Conning tower door damage

1

Bow damage (collision)

1

Strafing attack

1

Derangement of stern planes

1

Conning tower plating failure

1

Control cubicle derangement

1

Oil leakage from external tanks

1

Contamination of hydraulic system with salt water

1

Damage to torpedo tube fittings

1

Damage to torpedoes

1

Small caliber gunfire (40mm)

1

Total

49

2-11. Fifty-two U.S. submarines were lost from all causes during the period 7 December 1941 to 15 August 1945.1 A summary of these losses, with pertinent information where available, is presented in Appendix II. Of the total of fifty-two losses, at least nine were due to causes other than direct enemy action: four stranded on reefs during war patrols and were abandoned; two were lost due to operational or materiel casualties while on training exercises; one was lost by collision with a U.S. surface vessel while proceeding to her patrol area; and two were sunk by the malfunctioning of their own torpedoes. In addition, one was destroyed by Japanese bomb attack while under overhaul at Navy Yard, Cavite, P.I. The remaining forty-two submarines were lost at sea either through enemy action or for reasons unknown. The circumstances regarding the loss of six of these forty-two submarines are known from survivors' reports: two were scuttled after damage received by depth charge attack; one was scuttled after damage received by bomb attack; two were destroyed by mine explosions while running surfaced; and one was sunk by direct hits from medium caliber gunfire. The fate of the other thirty-six submarines is not definitely known. Assessment of the various sources of information enumerated in Appendix II of this report results in the following estimate: twenty-one submarines, probably or possibly sunk by depth charge and/or bomb attack; five probably or possibly sunk by mines; two possibly sunk by gunfire; one probably sunk by gunfire after being forced to the surface by depth charge attack; one probably destroyed, while surfaced, by Japanese torpedo attack; and six submarines whose loss remains in the unknown category.


1 Enemy submarines destroyed from all causes in World War II totaled 996, including 781 German, 85 Italian and 130 Japanese. (Statistics compiled by the British Admiralty and United States Navy Department Assessment Committees. Intelligence received from enemy sources after the termination of the war was considered in this evaluation.)

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2-12. Eleven cases of submarine loss or damage have been taken up in detail in this report and are grouped as follows: four cases of depth charge damage, including one loss; two cases of bomb damage, including one loss; one loss by torpedo damage; one case of damage by mine; one case of damage by medium caliber gunfire; one case of damage by collision and small caliber gunfire; and one case of damage by grounding while submerged. The cases have been selected to include not only the most serious instances of damage sustained by our submarines during World War II but also to illustrate the effect of underwater detonations at various points along the length of a submarine. The text of each case includes a narrative describing the action, the damage and its effect on the submarine, the damage control measures taken, the habitability aboard the submarine after damage, a discussion of the ordnance material which inflicted the damage, and such conclusions as may be drawn regarding materiel behavior.

2-13. Most of the information on the individual ship actions has been obtained from the respective Commanding Officers' patrol reports, the reports of war damage submitted by the Commanding Officers following the form of the Bureau's letter C-FS/L11-1(374); C-EN28/A2-11 of 17 April 1942 which was distributed to all vessels in the U.S. Navy, the supplementary war damage reports submitted by the various repair activities or Naval Shipyards, and survivors' reports in those cases where loss of the vessel occurred.

2-14. It is realized that the preparation of detailed reports during wartime often may be onerous to the individual concerned, especially when the press of other duties is extreme. However, it is through such reports that the forces afloat and field activities can keep the Department fully aware of significant developments and the need for design changes or materiel improvements. It is emphasized that reports of damage and loss have served as a basis for improvements in both design and equipment.

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SECTION III

JAPANESE ANTI-SUBMARINE WARFARE AND WEAPONS

3-1. Much interesting and hitherto unknown information on the Japanese anti-submarine warfare effort was gathered at the end of World War II by representatives of the U.S. Naval Technical Mission to Japan.1 The most striking feature commented upon was the enormous gulf between the Japanese conceptions of such warfare and their actual accomplishments. The Japanese high command had given consideration to almost every phase of advanced anti-submarine warfare. Much thought and research effort was directed towards the development of echo-ranging equipment, influence and acoustic proximity-fuzed depth charges, deep-setting depth charge pistols, chemical recorders, ultra high frequency voice radio, surface search radar for escort ships and aircraft, magnetic detection equipment for aircraft, ahead-thrown rockets and standardized and improved doctrine for surface and joint air-surface offensive action. Satisfactory solutions to many of these problems were obtained and limited production of equipment and operational training were undertaken.

3-2. Nevertheless, at the end of the war Japanese anti-submarine warfare was still being waged without appreciable benefit from the results of their research effort. Lack of production facilities, inability to maintain adequate supply lines, and the necessarily large allocation of production to aircraft for the final defense of the Empire home islands greatly affected the anti-submarine forces, but there also existed a failure on the part of operating personnel to use what they did have to best advantage.

3-3. Although the importance of use of radar to detect submarines was recognized, many escorts were never fitted with surface search radar due to lack of equipment.2 Even those escorts which had been equipped with search radar and improved echo-ranging devices were in most cases unable to obtain satisfactory results, due to defective equipment and poor training of maintenance and operating personnel. However, both combatant ships and escorts were generally provided quite early in the war with effective directional equipment to detect radar being used by U.S. submarines.2

3-4. The value of aircraft radar in anti-submarine work, both for search and blind attack, was also well recognized. Here again, their equipment was decidedly inferior and pilots generally were either poorly trained or lacked confidence in its use and are reported to have


1 NavTechJap Target Report, Index No. S-24, of 8 February 1946 (Japanese Anti-Submarine Warfare).
2 Japanese anti-submarine escorts did not begin receiving radar surface search equipment in quantity until about September 1944. Previous to that date, very few escorts were equipped with search radar since most of the available production was allocated to combatant ships. Radar-detection receivers were installed on most escorts by April 1944. -U.S. Strategic Bombing Survey, Naval Analysis Division, Interrogation No. 61.

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had but little success in radar bombing attacks. Airborne radar was first used in medium bombers as early as September 1943 but there was no large-scale employment of radar-equipped planes for antisubmarine work until the fall of 1944. Their equipment was reported to have been capable of detecting a surfaced submarine at a range of twelve miles. However, Japanese doctrine called for use of airborne radar only during night or low visibility conditions because visual search was still considered more reliable. Towards the end of the war, Japanese radar-equipped planes were making numerous contacts with cur submarines but few attacks resulted. In 1945 a few antisubmarine aircraft were also provided with radar detection receivers but the Japanese professed to have never reached the stage of homing on U.S. submarine radar. However, war patrol reports indicate that at least some enemy pilots achieved moderate success in using such equipment for initially detecting the presence of our submarines. Precise locating was probably then accomplished with aircraft search radar rather than radar detection equipment.

3-5. By late in 1943, the Japanese had successfully developed a magnetic airborne detector (MAD) and, commencing in March 1944 this equipment was put into operational use by both the Army and Navy for anti-submarine patrol.1 Range of detection was reported to have been about 120 meters under average conditions and about 250 meters was claimed under ideal conditions. Since expert pilots flew magnetic search planes only thirty to forty feet above the surface, the apparatus was therefore presumably capable of detecting a submarine at well over 300 feet submergence. Aircraft equipped with MAD were employed principally to search ahead of convoys or to exploit a submarine contact made by other means. Although it was planned to use such aircraft to sweep all heavily travelled convoy routes, lack of both aircraft and MAD equipment prevented this. The instrument was considered sufficiently reliable to warrant calling in surface craft whenever an initial contact had been established. The types of planes normally used for anti-submarine work, and equipped with MAD and/or radar when possible, were NELL, JAKE, KATE, JILL, DAVE, BETTY, ZEKE and EMILY.2 By the end of the war only about one-third of the shore based anti-submarine planes had MAD, about one-third had radar, and only a very few were equipped with both. Anti-submarine planes were very seldom fitted with guns which accounts for the low incidence of strafing attacks against U.S. submarines.

3-6. Only one small land-based "hunter-killer" air-surface group existed and even this was not organized until early 1945.3 The group covered the East China Sea between Formosa and Shanghai and was comprised of five surface ships (DE types) known as the 102nd Surface Squadron and about 20 Navy fighters (ZEKES) of the 934th Squadron,


1 NavTechJap Target Report, Index No. E-14 (Japanese Magnetic Airborne Detector).
2 U.S. Strategic Bombing Survey, Naval Analysis Division, Interrogations Nos. 200 and 371.
3 NavTechJap Target Report, Index No. S-24 (Japanese Anti-Submarine Warfare).

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Shanghai Air Force. These planes were equipped with both radar and magnetic airborne detectors. For routine patrol, the planes usually carried two 60 Kg. depth bombs and when sent out to attack a previously detected submarine carried one 250 Kg. depth bomb, although the 250 Kg. size depth bombs were also sometimes carried on patrol. Both the planes and surface escorts were provided with voice radio but could communicate only for short distances and frequently were unable to communicate at all due to technical difficulties.

3-7. The Japanese repeatedly demonstrated facility in detecting and locating submerged submarines by using sonar. Their underwater listening gear was fairly good and could frequently pick up our submarines at ranges of 2000 meters or more when the listening ship was stopped or proceeding at very slow speed. A damaged submarine with a high machinery noise level, such as a reduction gear click, could of coarse be heard at a far greater distance than an undamaged submarine running silent or creeping. Their echo-ranging equipment was of mediocre design, roughly corresponding to the early U.S. QC sonar of about 1937. The emphasis which the Japanese placed on sonar devices is clearly shown by the unnecessarily large amount of space allocated to such equipment in the already cramped quarters of their ships. At sea it was customary to man the hydrophone set continuously and to operate the echo-ranging gear at least fifteen minutes in every hour. Small escorts were generally provided only with listening gear, in some instances just a crude hydrophone lowered over the side. Japanese scientists were cognizant of density layers and temperature gradients in sea water and their effect on sound transmissions in echo-ranging detection work. However, anti-submarine vessels were not equipped with bathythermographs and no tactical use was apparently made of the small amount of information of operational value issued by the Japanese Hydrographic Office.

3-8. The depth charge was the primary Japanese surface ship antisubmarine weapon. Depth charges were placed aboard practically every type of ship capable of carrying them and even the smallest of patrol craft could generally be expected to have a few. Very slow craft used parachutes to reduce the sinking rate of their charges so as to reach a safe distance from the detonations. The Japanese used depth charge throwers extensively and even merchant ships were occasionally equipped with these. Fleet destroyers generally carried about 30 depth charges. Frigates (KAIBOKAN) could carry as many as 300 and were usually fitted with twelve single depth charge throwers, six to a side, and one stern rack. The Japanese PC-13 Class, by far the most numerous of their PC types, carried about 36 charges with two side throwers and one stern rack. Gun armament for the PC-13 Class consisted of one 8 cm. dual purpose and one twin 13mm machine gun.

3-9. There were only two types of depth charges in general use by the Japanese for surface ship launchings and both were almost exact copies of early British models of obsolete design. These were the Type 95, the Type 2, and the various modifications of each.1


1 Handbook of Japanese Explosive Ordnance, OpNav 30-3M of 15 August 1945 and Bureau of Ordnance Pamphlet 1507 of 20 April 1945.

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The Type 95 was the regular issue depth charge until the development of the Type 2. Although the Type 2 charge was adopted in 1942, Type 95 charges are known to have still been manufactured up to 1943. Both charges were probably in use during 1943 until available supplies of the Type 95 were finally exhausted. The Type 95 depth charge was cylindrical in shape, 17.75 inches in diameter and 30.5 inches long. The Type 95, Mod. 0 was filled with 220 pounds of Type 881 explosive and a Shimose2 booster; the Mod. 1 with 325 pounds of Type 973 or Type 984 explosive; and the Mod. 2 with 242 pounds of Type 15 explosive. The Type 2 depth charge was also cylindrical in shape, 17.56 inches in diameter and 30.5 inches long. The Type 2, Mod. 1, was filled with 357 pounds of Type 97 or Type 98 explosive and the Mod. 2 with 242 pounds of Type 1 explosive.

3-10. The pistols for both the Type 95 and Type 2 depth charges were also almost exact copies of early British models and both operated on the same depth setting and firing principle, although they were not interchangeable between the two types of charges.6 The firing mechanism of both pistols was actuated by the hydrostatic pressure of sea water flowing through a small orifice and slowly filling up an inner cylinder. Depth setting was accomplished by varying the size of the water inlet, thus determining the amount of time required to fill the inner cylinder. The smaller the inlet, the deeper the setting. The Type 95 depth charge pistol used early in the war could be set for operation only at depths of 98 feet, 98 feet with parachute, 197 feet, and "Safe". Later modification of this pistol provided for an additional setting of 292 feet. The maximum range of depth settings for the Type 2 depth charge pistol was much greater, a choice being available of 98 feet, 197 feet, 292 feet, 390 feet, 480 feet, and "Safe". It was apparently not possible with either type pistol to choose depth settings other than those enumerated above, even though detonation at some intermediate depth might be considered desirable.

3-11 No data are available as to how much variation could normally be expected between the prescribed depth settings on the pistols and the depths at which charge detonation would actually occur. The amount of error would naturally be affected by variations in sinking rates due to the following factors: (a) the method of launching, i.e., whether the charges were projected from throwers or dropped from stern racks; and (b) by the condition of the sea, i.e., whether still or disturbed. The accuracy


1 Type 88 explosive - 75% ammonium perchlorate, 16% ferro-silicon. More powerful than TNT. Power compares favorably with explosives containing aluminum.
2 Shimose -Almost pure picric acid. Slightly more powerful than TNT.
3 Type 97 explosive - 60% trinitrotoluene, 40% hexanitrodiphenylamine. Slightly less powerful than TNT.
4 Type 98 explosive - 60% trinitroanisole, 40% hexanitrodiphenylamine. Power is approximately that of TNT.
5 Type 1 explosive - 81% ammonium picrate, 16% aluminum. Power compares with that of Torpex or about one-third to one-half greater than TNT.
6 Handbook of Japanese Explosive Ordnance, OpNav 30-3M of 15 August 1945 and Bureau of Ordnance Pamphlet 1507 of 20 April 1945.

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with which the orifices in the pistols were initially machined would also affect the detonation depth. Tests conducted by the British on their early pistols indicated that discrepancies of as much as 60 feet should be expected for charges set for detonation at 250 foot depth. It should be noted that even though a Japanese depth charge were to come to rest in water more shallow than that for which its pistol had been set, it would still fire when sufficient water had seeped through the entry orifice to provide the minimum pressure required. This is believed to account for many of the delayed depth charge detonations which have been reported by U.S. submarines.

3-12. The maximum depth setting possible with the Type 95 depth charge is believed to have been 292 feet and the maximum setting normally used for the Type 2 charge was 390 feet. A proportionate number of charges with these maximum settings were usually included in each attack pattern. Our submarines reported only a few cases where depth charges were set for depths in excess of 400 feet.1 As the Japanese were unable to estimate the depth of a submerged target, no specific technique was developed for attacking submarines that took refuge in deep submergence. The only deep setting depth charge pistol developed was the Type 3, Models 1 and 2, designed for operation at 131, 262, 393, 524 and 656 feet.2 The design of this pistol was similar to that used in both the Type 95 and Type 2 depth charges but the extra time required to reach the greater depth was provided by a delay train initiated by the firing pin. However, issue to ships had not become general by the end of the war and no specific doctrine for its use had been developed.

3-13. Although the need for proximity-fuzed depth charges seems to have been appreciated, none were developed in time for operational use during the war. The Japanese Type 4 depth charge, designed for magnetic actuation, had been developed but trials on it were still in progress when the war ended.2 An acoustic type depth charge was also scheduled for development but work on this did not proceed beyond the preliminary design stage and no prototypes were made.

3-14. At least two types of anti-submarine explosive weapons designed for underwater tow by small surface vessels are known to have been developed and used by the Japanese, particularly early in the war. The first of these was called the "Yokosuka depth charge" and was set to explode upon contact with a submerged object. The charge was cylindrical in shape, about 1 foot in diameter by 5 feet in length, and contained 55 pounds of Type 88 explosive filler.3 The


1 While being depth charged on 4 July 1944, during her fifth patrol, SEAHORSE (SS304) reported that her DGDI indicated a few charges were definitely detonating below the ship even though her depth at that time was 470 feet. THREAD FIN (SS410) reported that while being depth charged on 28 March 1945, during her second patrol, over half of the detonations occurred at depths greater than 450 feet as indicated by DCDI.
2 NavTechJap Target Report, Index No. 0-08 of 16 December 1945 (Japanese Depth Charges).
3 Handbook of Japanese Explosive Ordnance, OpNav 30-3M of 15 August 1945.

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second weapon was designated by the Japanese as the Mark 2 Explosive Hook and, although developed primarily for minesweeping, was occasionally used for anti-submarine work. This device was a cast iron cylinder, 8 inches in diameter and ten inches long with four grapnel-like arms projecting from the main body, each 7-1/2 inches long. The body contained a charge varying from 8 to 19 pounds of Type 88 explosive.1 Firing was accomplished after the hook secured on a submerged target; the Mod. 0 either electrically by an observer on the towing ship or automatically when an additional tension of 550 pounds was put on the towing line, and the Mod. 1 by electrical control from the towing ship. Although several reports were received from U.S. submarines of small Japanese vessels apparently using these tow weapons, no large-scale employment was made and there is no information to indicate that damage was ever inflicted.2

3-15. Three sizes of aerial depth bombs were developed by the Japanese Navy specifically for anti-submarine work and were used for this purpose by both Army and Navy aircraft.3 These were designated by the Navy as Mark 2 bombs and by the Army as Type 4 bombs. They were fitted with anti-ricochet nose rings and had considerably higher explosive-loading factors than ordinary general purpose bombs. The smallest of the three was a 60 Kg. bomb, designated by the Navy as the Type 99, No. 6, Mk. 2, Mods. 0 and 1, and was loaded with 85 pounds of Type 98 explosive. These small bombs were carried primarily by planes on routine anti-submarine patrol and were considered to have a lethal range of 12 to 15 feet. The second was a 180 Kg. bomb designated as the Experimental 19, No. 25, Mk. 2, loaded with 308 pounds of Type 98 explosive. This bomb was developed primarily for use in conjunction with planes equipped with magnetic airborne detectors and was considered to have a lethal range of about 25 feet. The third and largest was a 250


1 Handbook of Japanese Explosive Ordnance, OpNav 30-3M of 15 August 1945.
2 On 8 September 1943, during her first patrol, BILLFISH (SS286) sighted a Japanese convoy escorted by a small converted merchantman and a sampan, the latter dragging two cables over the stern. During the subsequent depth charge attack, a distinct scraping sound was heard down the port side of the hull while at a depth of about 300 feet. This probably was an explosive sweep. In at least two instances, U.S. submarines were caught by grapnels but managed to escape without damage. (a) While submerged off the entrance to Kwajalein on 9 July 1942, during her fourth war patrol, THRESHER (SS200) was hooked in her after superstructure by an unknown type of Japanese grapnel. It was reported that the pull of the grapnel line made the boat noticeably light aft. The grapnel was finally cleared, after ten minutes, by running at high speed with full right rudder and by increasing depth to 350 feet, (b) On her sixth war patrol, CREVALLE (SS291) was hooked in her periscope shears by a crude four-pronged grapnel. The grapnel line broke and the grapnel itself fell to the deck and was recovered upon surfacing.
3 Handbook of Japanese Explosive Ordnance, OpNav 30-3M of 15 August 1945 and NavTechJap Target Report, Index No. 0-23 of December 1945 (Japanese Bombs).

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Kg. bomb designated as the Type 1, No. 25, Mk. 2, Model 1, Mods. 0 and 1, and was filled with 317 pounds of Type 98 explosive. This 250 Kg. bomb was considered to have a lethal range of about 33 feet and was generally only loaded on aircraft when a definite contact had been established by other planes or surface craft.

3-16. All three of the above Mark 2 depth bombs carried time rather than hydrostatic fuzes, and depth settings could only be varied by changing the fuze gaines prior to loading the bombs on aircraft. Four different fuze games with different time delays were used for anti-submarine work, each of which could be used with all standard Navy bomb fuzes, which in turn would fit any of the three Mark 2 bombs. The first game, the only variable setting design adopted by the Japanese, was designated as the Type 15 and could be set for detonation at any desired delay between 0 and 1.5 seconds after striking the surface of the water, equivalent to between 0 and about 50 foot depth.1 The desired setting had to be selected prior to insertion of the gaine in the bomb fuze. Although the Type 15 gaine was not developed specifically for anti-submarine bombs, it is known to have been used extensively for the purpose of attacking surfaced or submerging submarines. Each of the other three fuze gaines had a pre-fixed time delay and all three were designated as the Type 1, Mark 2 design. The Model 5 was set for detonation after 3.5 seconds delay, about 80 foot depth; the Model 1A after 6 seconds delay, about 150 foot depth; and the Model 1B after 17 seconds delay, about 300 foot depth.1 The Japanese referred to bombs fitted with the Models 5 and 1A gaines as "25 meter" and "45 meter" bombs and these were the types generally carried, although the gaines were naturally varied to suit the expected conditions.

3-17. When anti-submarine Mark 2 Navy bombs were not available, the Japanese substituted common types of 60 Kg. and 250 Kg. Navy GP bombs or Army 50 Kg., 100 Kg. and 250 Kg., Type 3 bombs. Army aircraft frequently carried a mixed load of their own Type 3 bombs along with Navy Mark 2 bombs, the Type 3 bombs being fuzed instantaneously, with short delays, or with a nose plug and a special 3.5 second delay tail fuze.

3-18. The Japanese directed considerable effort toward the development of gun projectiles for anti-submarine work which would continue an undisturbed trajectory after striking the water. After extensive tests in 1943, a flat-nosed projectile was adopted in which the area of the flat front was equal to half the area of the base. Projectiles of this non-ricochet type were produced for guns up to and including 8-inch.

3-19. Many U.S. submarines reported hearing small "sono-bomb" or "light" explosions while submerged and in contact with Japanese surface units. SALMON (SS182) likened the noise of such successive explosions to a "string of fire-crackers". These "sono-bombs" are believed to have been the Japanese Mark 3 and Mark 4 "Emit Sound Missiles" (HATSUONTO). This device consisted of a can 8 inches long and 5 inches in diameter, filled with Type 88 explosive. When dropped


1 The time delays given here are based on U.S. tests and do not agree with the figures contained in Japanese documents. The depths corresponding to these time delays have been computed for bombs dropped from an aircraft traveling at 100 knots at an elevation of 100 feet.

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into water, a small quantity of sodium under the top cap explodes, blowing the cap off and operating a pull igniter. Then after a short delay, the explosive charge detonates. These missiles were employed by the Japanese for the training of their own submarine crews, to simulate depth charges in an attempt to frighten Allied submarines away,1 and later were employed very successfully in sweeping U.S.-laid acoustic mine fields. Many of these "light" explosions heard just prior to depth charge detonations may also have been caused by the sound of depth charge throwers or possibly even gunfire in some cases.

3-20. Although mines were used by the Japanese as an anti-submarine measure and certainly constituted an appreciable hazard, such mining never became really extensive during any phase of the war, probably due to lack of mine-laying vessels.2 Both contact and controlled mine fields were laid in Empire coastal waters and harbors, the accesses to the Sea of Japan, the southern approaches to the Empire, Formosa and the Philippines. The most commonly used contact mine was the Type 93, containing 220 pounds of Type 88 or Type 1 explosive.3 This was a moored mine and was designed to arm only with tension on the mooring spindle, a drifting Type 93 mine therefore being disarmed except for those cases where the arming mechanism was locked closed by corrosion. The most commonly used controlled mine was the Type 92, containing 1100 pounds of Type 88 explosive.3 This was also a moored mine and could be either acoustically or magnetically monitored from shore or small vessels. The Japanese copied the design of two German magnetic and acoustic proximity-fuzed ground mines which were brought to Japan by a German vessel in September 1942 and produced their own adaptations by March 1944, both designed for planting by submarine. There is evidence that such mines were laid off Truk4 and in one area off the east coast of Australia,2 but aside from these two locations there is no indication that proximity-fuzed mines were used anywhere else. The development late in the war of the QLA sonar mine detector made possible the penetration of enemy minefields by our submarines and permitted spectacular operations in areas long considered invulnerable by the Japanese, such as the Sea of Japan.

3-21. The greatest disparity between the weapons employed in the Japanese anti-submarine program and ours was their failure to develop an ahead-thrown contact weapon similar to our Mark 10 Projector ("Hedgehog"). Some development work was done on ahead-thrown rockets fired in salvos of five from "rocket guns" but results were not satisfactory and the project was abandoned. This was the only type of ahead-thrown anti-submarine weapon under consideration by the Japanese. The U.S. Mark 10 "Hedgehog." projectile is fuzed to detonate on contact and the charge size (33 pounds Torpex) is


1 JICPOA captured Document No. 78745 records their use in this manner by a Japanese merchant ship and CinCPac-CinCPOA captured Item No. B-10202B also records such use by Japanese destroyers during the central action of the Battle for Leyte Gulf, 24-26 October 1944.
2 NavTechJap Target Report, Index No. 0-05 (Japanese Naval Mining Organization and Operational Techniques).
3 Handbook of Japanese Explosive Ordnance, OpNav 30-3M of 15 August 1945
4 Field Survey of Japanese Defenses at Truk, Part I, CinCPac-CinCPOA Bulletin 3-46 of 15 March 1946.

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such that rupture of the pressure hull is to be expected even when detonation occurs at the superstructure. The tactical problem is simplified, for usually contact is not lost prior to launching of a "Hedgehog" barrage and no interference with sound apparatus will occur until a hit is obtained. Probability studies based upon the various factors entering into an attack on a submerged submarine and statistical analysis of action reports indicate that a submarine's chance of surviving a depth charge barrage are at least four times as great as the probability of surviving a "Hedgehog" attack.1

3-22. The Japanese failed to achieve optimum use of their principal anti-submarine weapon, the depth charge, simply by repeatedly setting their pistols too shallow. There are many instances reported by our submarines, especially during the first two years of the war, in which depth charge patterns detonated directly overhead without causing appreciable damage but where an increase in depth setting would probably have resulted in fatal or serious damage. Above all, the Japanese generally lacked persistence in both their search efforts and exploitation of a positive contact, once made. They were prone to accept the slightest evidence that a submarine had been destroyed and then depart. Many a U.S. submarine owes its escape to the Japanese predisposition to take the most optimistic view.


1 From Operations Evaluation Group Report No. 51. This applies only to depth charges having pistols with preset depth settings, such as those used by the Japanese, and not to proximity-fuzed depth charges. An attack made with the latter is theoretically only slightly less effective than a "Hedgehog" attack.

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SECTION IV

U.S.S. PERCH (SS176)

Loss in Action

Java Sea

3 March 1942

Class

SS173

Builder

Electric Boat Co., Groton, Conn.

Commissioned

19 November 1936

Length (Overall)

300 ft. 6-3/4 in.

Beam (Extreme)

25 ft. 1-1/2 in.

Submergence Depth (Designed Maximum)(Axis)

250 ft.

Displacements

Standard

1330 tons

Emergency Diving Trim

1725 tons

Submerged

2005 tons

Draft (Mean, Emergency Diving Trim)

16 ft. 11 in.

Type of Propulsion

Diesel Electric Reduction Drive

Main Engines (4)

Winton 16-201A

Main Motors (8) and Generators (4)

General Electric Co.

References:

(a) Enclosure (B) to ComSubsPacAdmin secret ltr. FF12-10(A)/A4-(1)/A16-2, Serial 00349 of 21 September 1945 (Commanding Officer PERCH Statement Concerning Loss of Vessel).
(b) ComSubsPacAdmin ltr. FF12-10(A)/A16-2, Serial 3599 of 12 October 1945 (Statements of Two PERCH Crew Members Concerning Loss of Vessel).
(c) ComSubsPac Report Entitled "Enemy Anti-Submarine Measures", no date or file number given (Account of Loss of PERCH).
(d) Account of Loss of PERCH as Related to Cdr. I.F. Duff, (MC), USNR, by Lt.Cdr. J.J. Vandergrift, Jr., USN, on 5 April 1946.

Photograph No. 4-1

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4-1. On 2 March 1942, while operating in the Java Sea on her second war patrol, PERCH sustained severe depth charge damage which prevented further submerged operations and reduced her maximum surface speed to about 5 knots. Shortly after dawn on 3 March, PERCH was deliberately scuttled by her own crew to prevent imminent capture by Japanese surface forces. This report is based on the information contained in references (a) through (d). These references are accounts furnished from memory by various survivors of PERCH upon their release from Japanese prisoner of war camps at the end of the war, almost four years after the action took place. It naturally follows that the source data are not as complete and cannot be considered to have the same degree of accuracy as formal war damage and action reports written shortly after an action.

4-2. After normal refit, PERCH departed Port Darwin, Australia, for her second war patrol on 3 February 1942. At this time the Japanese campaign to secure the Netherlands East Indies was in full swing. PERCH was directed to patrol and perform reconnaissance in various positions in the Java and Flores Seas as part of the force then attempting to defend Java.

4-3. On the night of 25 February 1942, while patrolling the southern approaches to Kendaris, Celebes, PERCH sighted a Japanese supply ship and commenced approach for a surface attack. However, the enemy ship opened fire and scored one three-inch shell hit on PERCH which struck the light fairwater plating just forward of the conning tower proper and detonated inside the "doghouse". The pressure-proof radio antenna trunk and 200-pound air line to the whistle were ruptured, several electrical cables were cut by shrapnel, and the pressure-proof magnetic compass trunk system was flooded. Action was terminated without further damage. Temporary repairs were made by ship's force to the radio antenna trunk which permitted subsequent radio transmission.

4-4. The following night, PERCH was ordered westward into the Java Sea after a large Japanese convoy of troopships had been sighted near Bawean Island with apparent intentions of landing forces on Java. On 27 February, the Battle of the Java Sea occurred, ending all organized Allied surface resistance in the East Indies area. The Japanese landed on the northern coast of Java on 28 February. That night PERCH received notification of the exact landing point of the convoy and was ordered to disregard previously assigned areas and to attack.

4-5. On the next night, 1 March, PERCH was still proceeding west toward the designated landing area, and had reached a position about twelve miles northwest of Soerabaja, when two Japanese destroyers were sighted. PERCH was at this time running on the surface so she made a quick dive to avoid detection. There was a full moon and visibility conditions were excellent. The destroyers passed well clear astern and out of torpedo range but turned back after proceeding about four or five miles. One of the destroyers then came in close

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on a course favorable for stern torpedo shots and PERCH made ready for attack, taking frequent periscope observations. However, on the last periscope check before firing, it was noted that the target destroyer, which was distant about 800 to 1000 yards at this time, had obviously detected PERCH and was charging in at high speed for an attack.

4-6. The Commanding Officer, believing he was in 200 feet of water, immediately ordered depth increased to 180 feet. When PERCH had reached a depth of about 90 to 100 feet, however, the destroyer passed directly overhead and dropped several depth charges. This first pattern was not close and caused no appreciable damage. Shortly afterwards, PERCH struck bottom at about 147 feet depth with her propellers still turning over and while in this position received a second pattern of four depth charges, this time very close. This group of charges was apparently dropped by the second destroyer. Considerable damage was sustained aft and all main motor field relays tripped, causing temporary loss of propulsion. While still on the bottom, a third and final depth charge pattern was received very close aboard amidships. The enemy destroyers then ceased further attacks, apparently convinced that PERCH had been destroyed, although they remained in the immediate area.1

4-7. Extensive damage was caused by the second and third depth charge patterns. As mentioned previously, all main motor field relays tripped, causing temporary loss of propulsion until they were reset. The pressure hull was dished inward by as much as 2-1/2 inches in the after battery compartment on the starboard side forward and the port side aft. The conning tower plating was depressed to a depth of about 2 inches over an area about three feet by one foot. The engine room hatch, conning tower hatch and conning tower door gaskets were crimped and leaked steadily. The inboard hull flapper valves for the ship's supply ventilation system and the engine air induction system were jammed closed. MBT No. 5 master vent valve also jammed in the closed position. The battery exhaust system outboard valve apparently opened momentarily upon one or more close detonations and sea water flooded the exhaust duct section in the control room, some of it splashing onto the fire control panel. The high pressure air bank in the after battery well commenced to leak heavily. Both main batteries showed full ground. No. 2 periscope could not be moved. No. 1 periscope could be raised and lowered but required the combined effort of four men to train it. Ninety per cent of the gauges and instruments in the engine room were broken or deranged and several depth gauges were also put out of commission. Considerable inboard leakage occurred through a cracked weld at the hull flange of the air conditioning circulating water supply system.


1 A list of anti-submarine attacks, received from the Japanese at the end of the war, which were assessed as resulting in "positive" sinkings, mentions several attacks in this area on 1-2 March 1942 but no amplifying data was submitted and none can be definitely identified as having been made on PERCH.

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4-8. It is interesting to note that although this first series of attacks was sufficiently severe to cause considerable permanent hull deformation, the watertight integrity of the hull proper remained substantially intact and no serious damage was sustained at this time by either the submerged propulsion plant or vital auxiliary systems and equipment. It is probable that all of the depth charges were set for detonation at 98 feet since the next deeper setting available on Japanese charges was 197 feet and the depth of the water in which the attack occurred was reported to have been only about 150 feet, a fact certainly known to the enemy.

4-9. Shortly after receiving the third depth charge pattern, PERCH got underway again and by using evasive tactics managed to lose both destroyers in about two hours. At about 0300, 2 March, PERCH surfaced and an inspection topside was made. All the radio antennae insulators were found to have been broken. An armful of fragments from the depth charge cases was picked up on deck. Both periscope head windows were shattered and both periscope tubes had completely flooded. The bridge blinker light was found compressed flat.

4-10. No. 1 main Diesel engine ran away on starting and the camshaft of No. 4 main engine was found broken, leaving only two main engines in operating condition. No. 2 main engine was put on battery charge and No. 3 main engine was put on propulsion. PERCH once again proceeded in the direction of the Japanese landing on Java, still with intentions of attacking the enemy. Repairs to damage were started where possible and the high pressure air banks were replenished.

4-11. At about 0400, approximately two hours before sunrise, the same two Japanese destroyers were again sighted. PERCH immediately submerged and lay on the bottom in about 200 feet of water with all machinery secured. This course was chosen rather than evasive running for the machinery had developed a high noise level as a result of the previous attack and it would have been necessary to use the very noisy trim pump almost constantly in order to maintain depth control.

4-12. Unfortunately, the enemy destroyers had either sighted PERCH before she submerged or had established definite sound contact, for several depth charge attacks were immediately delivered, resulting in serious damage. An attempt was then made to get under way and take evasive action but the propulsion plant was found to be inoperative, due to short circuits in the electrical control gear or damage to the main motors, and PERCH was forced to remain on the bottom. Following this series of attacks, the enemy destroyers apparently decided to postpone further efforts until daylight but in the meantime made frequent checks on PERCH's position by echo-ranging.

4-13. Shortly after sunrise, three more attacks were delivered, the final pattern of three charges at about 0830 being the most severe of all. The enemy destroyers then left the area, probably again certain that they had destroyed their target.

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4-14. Reference (b) reports that "there was hardly any part of the boat that had not in some way been damaged." Only one of the four main Diesel engines was not damaged beyond immediate repair. However, the two auxiliary engines (Winton 6-241) were still operable. The port reduction gear casing was cracked and lost lubricating oil constantly. As mentioned above, the submerged propulsion plant was put out of commission due to deranged control equipment and motor damage. Numerous holding down bolts on the main motors, main generators and main engines were reported to have broken.

4-15. The pressure hull overhead in the forward battery compartment was dished inward to a depth of about 1-1/2 inches over an area of about 6 feet by 2-1/2 feet and many other new indentations occurred at various points along the length of the ship in addition to those received from the first series of attacks. In no place, however, was the pressure hull torn or ruptured.

4-16. All lighting was cut off by a close detonation but was partially restored after a short while. Many auxiliary motors were short-circuited or deranged. There were at least nineteen cracked jars in the forward battery and one in the after battery, causing loss of electrolyte and full grounds. All of the electric alarm and telephone circuits were out of commission.

4-17. One particularly close detonation forward caused the bow planes, then on 20 degrees rise angle, to partially rig in, damaging the bow plane rigging system. The holding down studs for the bow plane tilting motor backed off or elongated and the shims dropped out. The planes were thereafter tilted by hand. The radio antenna trunk flooded. The JK sound head was put out of commission. Torpedoes loaded in forward tubes Nos. 1 and 2 and one torpedo loaded in an after tube were reported to have made "hot" runs. Many torpedo tube doors were jammed. All water closet bowls (porcelain) were shattered. The engine room deck support stanchions were torn away at their overhead connection to the pressure hull.

4-18. Both Nos. 1 and 4 high pressure air banks bled completely down through numerous leaks and various other air system leaks developed throughout the boat. The increase in pressure of the atmosphere within the boat from these air leaks was considerable although it could not be measured since the barometer was broken. The excessive air pressure, extreme heat, and high humidity caused much discomfort and had a deleterious effect on all hands.

4-19. Sea water leakage into the pressure hull also increased markedly. Strips a quarter of an inch square in cross section had been cut from the conning tower and forward escape trunk door gaskets. Leakage around these doors and the conning tower and engine room access hatches became serious. The air conditioning circulating water supply hull flange crack, caused by the first series of attacks, became enlarged and the flange studs elongated or the nuts backed off, further augmenting the leakage at this point. Many

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other salt water systems throughout the ship also developed leaks. Fuel tanks are reported to have leaked externally.

4-20. PERCH remained on the bottom until after sunset on the evening of 2 March. Order was restored and repairs to equipment were attempted where possible during this period. Damage to one of the main motors was isolated and battery propulsion was regained on both shafts. Bilges were kept pumped down to avoid grounding electrical machinery. The forward and after trim tanks and No. 2 auxiliary tank were pumped dry.

4-21. At about 2000 on 2 March, after approximately sixteen hours submerged, the first attempt was made to surface. The boat did not move, however, for the downward thrust of the depth charge attacks had partially embedded the hull in the soft ocean floor and many master vent valves leaked or could not be seated, rendering it impossible to blow the ballast tanks since air introduced into the tanks escaped through the risers. As an indication that the boat had been forced deep into the soft bottom, it was noted during the final severe depth charge pattern that PERCH's remaining depth gauge suddenly changed reading from 200 feet to 228 feet and then to 230 feet, although this might have been due to derangement of the gauge itself.

4-22. By closing the emergency vent valves and going alternately ahead and astern at maximum revolutions on both shafts, PERCH finally broke loose from the bottom on her third attempt. These efforts consumed a period of about one hour and all high pressure air was expended except for one partially filled bank. The enemy was not in sight upon surfacing.

4-23. After successively attempting to start all four main engines, only No. 3 engine was found operable and PERCH got under way at a speed of about 5 knots. About half of the holding down bolts for the No. 3 engine had broken and the engine vibrated so badly that the head covers raised one inch. The batteries were put on charge with the undamaged auxiliary Diesel generators. The steering gear was behaving erratically at this time, for the rudder could be moved from the full left position only with difficulty and upon reaching amidships would suddenly snap over hard against the starboard stops. MBT No. 2 was leaking heavily from sea. Even on the surface, sea water leakage into the hull was sufficient to keep both the trim and drain pumps operating at full capacity. All gyro-repeaters had been deranged and steering was accomplished by relaying word to the bridge from a man stationed at the master gyrocompass in the control room. Many depth charge case fragments were again found on the deck topside.

4-24. After quickly surveying the condition of the boat, the Commanding Officer at this time set up procedure for scuttling the ship if it became necessary. Repairs were attempted where feasible. Men working in the engine room were unable to tolerate the extreme heat and had to be relieved frequently so they could go topside to recover.

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4-25. PERCH continued to run on the surface throughout the night. In order to determine whether or not the boat could submerge, it was decided to try a running dive while still dark. This was attempted about an hour and a half before sunrise on 3 March. However, in spite of having deliberately tried to make the ship light so that trim could be established by flooding in on the dive, PERCH was found very heavy aft. The boat assumed a large up angle and water entered in large volume around the conning tower and engine room hatches which failed to seat properly. When a depth of 75 feet had been reached and the two hatches still showed no sign of seating themselves by hydrostatic pressure, the boat was surfaced. Reference (a) reports that at this time there was still only one full air bank. By the time PERCH reached the surface, the water level in the engine room bilges was almost to the main generators.

4-26. It was found that the conning tower hatch lacked complete seating by a gap of about 3/8 inch. The hatch dogs were removed and adjusted but with no improvement. This work was handicapped by the necessity of having to keep the ship darkened to avoid detection. Once again the dogs were removed, but while attempting further adjustments, three Japanese destroyers came upon the scene and opened fire on PERCH. Five or six shells landed in the water nearby.

4-27. PERCH attempted to engage the enemy with her three-inch deck gun but it could neither be trained nor elevated and the sights were shattered. Torpedoes could not be fired. In this helpless condition, with no fire power, obviously unable to submerge and capable of making only 5 knots on the surface, the Commanding Officer decided to abandon and scuttle the boat at once. All hands were ordered topside. The diving alarm was sounded and the vents were opened by one officer who had remained below for this purpose. The men on deck literally felt the ship, which was still going ahead at one-third speed on her batteries, go out from under them. All the men leaving the ship were equipped with life jackets and some in addition carried escape "lungs" and flashlights. The officer who manned the vents had to fight his way out through the open conning tower hatch against the incoming water. PERCH went down about 100 yards from the survivors shortly before dawn on 3 March 1942, with her colors flying.

4-28. As far as is known, the entire crew was taken aboard by the Japanese destroyers during the morning. Most of the survivors were imprisoned until the end of the war at Makassar, Celebes, although a few were later transferred to various camps in Japan. Fifty-three officers and men are known to have survived to the end of the war.

4-29. In analyzing the many factors involved in the loss of PERCH, it appears that the conning tower and engine room hatch damage was the only reason the boat was unable to submerge upon sighting the enemy destroyers on the morning of 3 March. This case is an excellent illustration of the unhappy fact that but one casualty to a vital part of a submarine can cause its loss.

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4-30. However, even had PERCH been able to submerge, it is problematical whether she could have escaped eventually. For example, the extent of external leakage from the oil tanks is not known. This alone might have been sufficient to disclose her exact location to the enemy and in such shallow waters it is likely that she would not again have survived a series of well executed depth charge attacks. Even had the destroyers not discovered PERCH on the morning of 3 March, in the event that repairs could not be made to the damaged hatches it is doubtful that she could have made a surface escape with only one engine, for the Java Sea was at this time completely controlled by the Japanese.

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Photo 4-1: PERCH (SS176). Photo taken in 1940.

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SECTION V

U.S.S. KINGFISH (SS234)

Depth Charge Damage

Off Formosa 23 March 1943

Class

SS212

Builder

U.S. Navy Yard, Portsmouth, N. H.

Commissioned

20 May 1942

Length (Overall)

311 ft. 8 in.

Beam (Extreme)

27 ft. 3 in.

Submergence Depth (Designed Maximum)(Axis)

300 ft.

Displacements

Standard

1525 tons

Emergency Diving Trim

2050 tons

Submerged

2415 tons

Draft (Mean, Emergency Diving Trim)

16 ft. 10 in.

Type of Propulsion

Diesel Electric Reduction Drive

Main Engines (4)

Fairbanks-Morse 38-D-8-1/8

Main Motors (4) and Generators (4)

Elliott Co.

References:

(a) C.O. KINGFISH conf. ltr. SS234/A12-1/A-16-3/A9 of 8 April 1943 (Report of War Patrol Number Three).
(b) Comdt. Navy Yard Mare Island conf. ltr. SS234/L11-1 (33-558674) of 17 May 1943 with enclosures thereto (Supplementary Report on KINGFISH War Damage).
(c) BuOrd (Re6) Memorandum dated 4 May 1943 (Report on Inspection of KINGFISH Damage and Interview of Ship's Officers by Dr. A. B. Focke).

Photographs Nos. 5-1 through 5-16 (furnished by Navy Yard, Mare Island).

PLATE V

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5-1. On 23 March 1943, while on her third war patrol, KINGFISH underwent a severe depth charge attack north of Formosa. A total of over forty depth charges were dropped in the vicinity of KINGFISH during the 7-1/2 hour period she was under attack. Serious damage was caused by the final pattern of six charges, two of which detonated close over the after portion of the ship while the boat was running at 300 foot depth, forcing her to the bottom in 350 feet of water. In spite of sustaining considerable permanent pressure hull deformation in various areas and widespread interior damage, no vital systems or machinery were put out of commission and watertight integrity remained substantially intact. Six hours after the termination of the attack, and without undue difficulty, KINGFISH was able to surface and clear the area at full power on all main engines. This report is based on the information contained in the references and on an informal interview with the then Commanding Officer. The Photographs were furnished by the U.S. Navy Yard, Mare Island. The PLATE was prepared by the Bureau from data contained in the enclosures to reference (b).

5-2. KINGFISH arrived at Pearl Harbor from her second war patrol on 23 January 1943. Normal refit was undertaken by repair forces of the Submarine Base, Pearl Harbor, and completed on 7 February. Deperming, sound tests and training were completed on 15 February and, on 16 February, KINGFISH departed Pearl Harbor for Midway, arriving on 20 February. Minor voyage repairs were made there and fuel and lubricating oil were topped off. She departed Midway on 21 February for her third war patrol and arrived on station in the wafers adjacent to the Island of Formosa on 7 March, destroying a 250-ton enemy trawler by three-inch gunfire attack on 4 March while en route. On 17 March KINGFISH sank a medium-sized freighter by two torpedo hits during a night submerged periscope attack and on 19 March sank a medium-sized troop transport by two torpedo hits during a daylight submerged periscope attack. Three other attacks were made but no hits were obtained, apparently due to faulty torpedo performance.

5-3. At 0300 on 23 March, while surfaced about 60 miles north of Formosa, lat. 26° 20' N., long. 121° 55' E., KINGFISH sighted at a range of approximately 5000 yards what appeared to be either a small Japanese destroyer or minelayer of about 1200 tons. Battle stations were manned at once and an attempt was made to gain a position ahead of the enemy ship for a dawn attack. However, at 0325, the target ship detected KINGFISH and headed toward her at a speed of about 16 knots. KINGFISH was able to draw away slowly at flank speed but twenty minutes later, at 0345, the enemy illuminated her with a searchlight. At this point, KINGFISH submerged to a depth of 250 feet, rigged ship for depth charge attack and silent running, and commenced evasive action.

5-4. These maneuvers were unsuccessful, however, for at 0448 KINGFISH received the first of a long series of depth charge attacks.1


1 A list of anti-submarine attacks received from the Japanese at the end of the war, and assessed as resulting in "positive" sinkings, contains no mention of this series of attacks on KINGFISH.

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Evasive tactics were continued at a depth of 300 feet but the enemy was both tenacious and experienced, and seemed to have no difficulty maintaining contact. He appeared to use sonic listening for determination of azimuth and echo-ranging for distance. Sound conditions were excellent. Three attempts were made by KINGFISH to approach the surface and fire circular run torpedo shots, but each time the enemy counterattacked before a depth of 100 feet was reached and this plan had to be abandoned. At 0752 the screws of a second ship were heard. This vessel took no direct action, apparently having no depth charges, and used no sound gear other than a fathometer. A total of 41 depth charges in eight separate patterns were dropped during the entire 7-1/2 hour period KINGFISH was under attack. Attacks were spaced at about one hour intervals and consisted of from 3 to 8 charges each.

5-5. No serious damage was sustained until the final attack at 1227, at which time a pattern of six depth charges was received very close aboard while the ship was running at 300 foot depth. The charges were dropped in pairs, the first two detonating over the after portion of the ship, dishing in the pressure hull and forcing KINGFISH to the bottom in about 350 feet of water. The second pair of charges detonated forward of and above the ship, causing but little damage. The third pair of charges was delayed nearly a minute and detonated forward, also causing only minor damage. Following this attack the enemy vessels stayed in the vicinity for several more hours, occasionally making transits across KINGFISH, but did not drop any additional charges.

5-6. The two close detonations aft, at 1227, caused severe vertical flexural vibrations of the hull as a whole. Reference (a) reports that the ship "humped like a measuring worm" and was forced considerably off her course. Reference (c) notes that there were "three strong up and down vibrations, followed by gradually decreasing ones". This type of vibration had not been observed during any previous depth charge attacks experienced by KINGFISH. The motions were of such magnitude as to throw two men from their bunks to the deck and other personnel lost their footing even though braced in anticipation of shock. Some 12 of the 41 charges dropped on KINGFISH were close enough to cause at least minor damage. The more distant of these 12 charges broke lights, stopped clocks, jarred cork insulation from the hull and, in general, caused lightly attached hull fittings to come loose. Closer-in charges caused numerous hull valves throughout the boat to open. Two observers claimed to have seen flame shoot past the breech door of one of the after torpedo tubes coincident with the detonations of the two very close depth charges aft. Smoke and fumes were also detected in the after torpedo room.1

5-7. All of the depth charges dropped by the enemy were probably of the Type 2, Mod. 1 design containing 357 pounds of Type 98 explosive. The two close detonations aft at 1227, which were responsible for most of the damage, are believed to have been centered as follows: One charge at the after end of the ship about ten feet above the deck level, causing the phenomena observed at the torpedo tube and forcing the


1 For further discussion, see paragraphs 15-18, 15-19 and 15-20 .

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stern down with resultant plating failure under compression at the lower outer hull between frames 103 and 108; the second charge approximately 40 feet directly above the hull at about frame 83, causing the pressure hull structural deformation which occurred in way of the forward engine room.

5-8. Upon being forced to the bottom, the ship was silenced completely and, while awaiting darkness, the crew made temporary repairs to damage where feasible. Plans were prepared for scuttling ship in case escape proved impossible after surfacing. In partial execution of these plans, the ECM was destroyed and the torpedo data computer was rendered inoperative by disabling the forward angle solver. Only two after effects of the attack caused serious concern at this time. The first was the profuse leakage of sea water which occurred in both engine rooms through the distorted engine induction hull valves, the external induction system having completely flooded. This leakage was almost completely stopped within 15 minutes by forcing the valves hard against their seats with the aid of chain falls. The second was the high pressure air leakage into the boat through a damaged fitting in the No. 3 air bank piping and at partially opened cone joint connections at the high pressure air manifolds in the control room. The air pressure within the boat increased markedly as a result of this leakage. Since all manometers and barometers were disabled, the amount of increase in air pressure could not be determined but calculations indicate that it was of the order of eight or more pounds per square inch.

5-9. At 1500 and again at 1800 the screws of an enemy vessel were heard plainly through the hull for periods of about 15 minutes although no more depth charges were dropped. At 1848, after dark, KINGFISH manned battle stations and surfaced. A patrol vessel of about 1000 tons was sighted lying-to approximately 2000 yards off the starboard bow. No difficulty was experienced in immediately getting underway and the area was cleared at flank speed using all four main engines. Fortunately no opposition was encountered from the enemy patrol craft.

5-10. Since the damage made further offensive action impossible, KINGFISH returned to base for repairs, arriving at Pearl Harbor on 9 April 1943. The return run was made submerged during daylight hours for the first two days. The only difficulty encountered in these submerged operations was the minor leakage into the engine air induction system and the complete flooding of the ship's supply ventilation system outboard piping which occurred on each dive.

5-11. Damage to the ship was of varied nature and of general extent throughout (PLATE V and Photos 5-1 through 5-16), but was most severe in the vicinity of the forward and after engine rooms, conning tower, and after torpedo room. Structural damage in these areas consisted of minor distortion to the circularity of the pressure hull and numerous depressions of the hull plating between frames. Damage in way of the engine rooms extended from frames 77 to 93, with the more

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severe depressions occurring in the upper pressure hull plating between tank tops from frames 80 to 87. Depressions of 1-1/4 inch maximum depth occurred at frame 86 on the forward engine room riveted access patch and between frames 82 and 83 (Photos 5-1 and 5-3). The keystone frame connections at frames 85 and 86, in way of the hard patch, pulled slightly apart due to depression of the hull in this vicinity (Photo 5-2). Although the riveted butt and seam connections appeared to be the weakest points of this hard patch, it is significant to note that only minor leakage developed around the rivets in spite of the considerable distortion and impact to which this region of the hull was subjected. Small leaks also developed around the forward and after battery compartment bolted access patches, although these were remote from areas of hull damage. Except for the minor distortion which occurred to frame 83 (Photo 5-3), all frames appeared to retain their proper shape.

5-12. Local depressions of the outer shell plating up to a maximum depth of about 1 inch occurred between frames, port and starboard, in way of three after lubricating oil tanks as follows: motor and reduction gear lubricating oil sump tanks Nos. 1 and 2, "A" strake (30-pound MS) between frames 103-105; motor and reduction gear lubricating oil stowage tank, "A" strake (30-pound MS) between frames 105-107; engine lubricating oil stowage tank No. 5, "B" strake (20-pound MS) between frames 107-108 (PLATE V, Photo 5-4). These areas are subject to full sea pressure and were structurally somewhat weaker than corresponding outer hull structure in way of the auxiliary and safety tanks. The depressed areas of the "A" strake between frames 104-106 occurred in 30-pound plating backed by frames spaced on 30-inch centers instead of 24-inch centers as in the auxiliary and safety tanks and the "B" strake depressions between frames 107-108 occurred in way of 20-pound plating on 24-inch frame spacing instead of 30-pound plating as in the safety and auxiliary tanks.1 The deformations in these areas could have been caused by either direct explosive loading from a close detonation or, possibly, as a result of the strong flexural vibrations reported by the ship, the depressed area occurring at the quarter length or natural node of vibration of the ship's structure as a whole.

5-13. Farther aft, minor depressions occurred in the shell plating just above the stern tubes, port and starboard, and the top of the after trim tank was indented to a depth of approximately 1 inch in two small areas, port and starboard, between frames 127 and 128. The trim tank depressions were located at the points where the port and starboard propeller guard struts had been originally attached. These guards had previously been permanently removed on KINGFISH when it was found that the plating in way of the strut attachments had cracked, due to vibration. The cracks were welded up and covered with small doubter plates, causing local hard spots in the structural continuity, and this probably accounted for the local deformation at those points. The trim tank did not leak, however.


1 While not critical, as a result of KINGFISH's experience it was considered that the outer hull plating in these areas should be reinforced. ShipAlt SS192 of 19 May 1943 therefore authorized the installation of 20-pound MS doubters in way of these lubricating oil tanks on SS18-284. SS285 and subsequent submarines were designed with heavier plating in these areas.

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5-14. Investigation of the ship's structure in the after torpedo room disclosed minor variation from the designed offsets and the top of MBT No. 7 was dished upward between frames 110 and 118 to a maximum of 15/32 inch. No evidence of buckling of the tank top stiffeners could be found, however. The movement of the tank top forced the torpedo stowage and loading tracks out of alignment with the torpedo tubes to such an extent that they later had to be cut adrift and reset. The MBT No. 1 tank top plating in the forward torpedo room was also pushed upward, but to a lesser extent. However, realignment of the forward torpedo tracks was also found necessary in order to secure satisfactory torpedo handling and loading.

5-15. Both the end bulkheads and shell plating of the conning tower cylindrical structure sustained permanent deformation. The conning tower bulkheads installed on KINGFISH at this time were of the type having a 15-pound medium steel inwardly dished plate acting as the bulkhead proper with a heavy forged ring connecting the periphery of the dished plate to the cylindrical wrapper plate (Photo 5-5). It was reported by the ship's officers that the forward bulkhead was initially forced in to such an extent that the steering wheel moved approximately two inches aft relative to the lockers on the port side, and that the locker drawers could not be opened due to interference with the wheel. During the trip back to base, however, the ship reported that the amount of bulkhead deformation gradually reduced until, upon arrival, it was only about one-third the original amount. Offsets taken at the Navy Yard, Mare Island, one month after the damage occurred indicated a variation from the designed offsets of only 1/2 inch at the forward bulkhead and 3/4 inch at the after bulkhead. These figures mean little, however, since the dished plates are frequently shaped with at least that much deviation from the designed radius of curvature.1 No means were available for determining the actual bulkhead offsets as originally fabricated and installed at the building yard. It is certain, however, from the known change which occurred in the relative positions of the steering wheel and lockers, that the forward bulkhead was deformed considerably.

5-16. It is interesting to note that the 20-inch by 38-inch six-dog watertight escape door fitted in the after bulkhead of the conning tower remained substantially intact and that no leakage occurred in spite of the probable large bulkhead deflection. The door frame was sufficiently distorted, however, so that the door dogs bound against the seat and prevented the door from opening more than a few inches (Photo 5-5). It was fortunate that the door seat was wide and flat, for had it been narrow or rounded, as was the case with earlier designs, the door gasket very probably would have been cut or blown out when the bulkhead deformed and serious leakage into the conning tower would have resulted.2


1 Allowable tolerance from designed radius of curvature for such bulkheads was plus one inch and minus nothing—BuShips dispatch 122222 of June 1943.
2 As a result of this casualty, similar war damage experiences of other submarines, and tests conducted at the Navy Yard, Portsmouth, conning tower doors were removed on all submarines per BuShips ltr. SS/S16-2(515) of 30 April 1943. This was accomplished on ships in service by completely renewing the after bulkhead of the conning tower. Such doors were omitted from the designs for SS285 and subsequent submarines.

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5-17. The conning tower plating was slightly deformed at the top after portion of the cylinder. The maximum depression occurring in this region was only 3/8 inch, located between the after bulkhead forged ring and the hoop stiffener just forward. Cork insulation under the depressed areas was cracked and loosened. A check of the general circularity of the conning tower cylinder showed that it conformed to the designed allowable diametrical tolerance of one-half the plate thickness.

5-18. Damage to structure and fittings external to the pressure hull was negligible. Two eyeports in the pilothouse were shattered and the light access door leading from the pilothouse to the forward gun platform was sprung so that it was difficult to close. The after torpedo room deck loading skid was jarred loose and lost overboard. No other damage worthy of mention was sustained by the superstructure, conning tower fairwater or bridge.

5-19. Damage to external hatch covers occurred in only two places. The forward escape trunk upper hatch cover was warped downward sufficiently to partially unseat itself and the trunk completely flooded. The hatch dogging mechanism was also bent, apparently when the cover was forced up under the action of one or more depth charges. Although the trunk flooded, the lower hatch held tight and no water entered the ship. No damage was sustained by the after watertight door of this escape trunk. The upper conning tower hatch cover seat was found to be distorted slightly but no leakage occurred. An interesting minor effect of depth charge impact was that the pins securing the upper handwheels to the squared ends of the worm shafts sheared off on both the forward and after escape trunk hatches. Aside from the conning tower bulkhead door frame, previously mentioned, no other damage occurred to external hatches, seats, gaskets or operating gear. However, the transverse struts fitted at the forward and after torpedo loading hatch bosses showed evidence of excessive compression, for their threads were jammed together to such a degree that subsequent removal was difficult. Three covers on topside pressure-proof ammunition stowages were distorted sufficiently to permit the stowages to flood. These were the two 3-inch/50 cal. ready service ammunition stowages located in the forward end of the conning tower fairwater and one 20mm ready service stowage located on the bridge (Photo 5-6).

5-20. There was considerable leakage of water into several interior compartments, but due to prompt damage control measures, at no time throughout the attack did flooding endanger the safety of the ship. Leakage occurred as follows:

(a) Into the forward torpedo room to a depth of 2 inches over the top of MBT No. 1 through a sound projector electrical cable hole.

(b) Into the pump room to a depth of 4 inches through the SJ radar mast stuffing box, the conning tower voice tube and an electric cable to the bridge, all of the water draining down from the conning tower bilge.

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(c) Into both engine rooms to the level of the lower floor plates through the main engine air induction hull valves.

(d) Into the motor room through the starboard stern tube stuffing gland to a level 2 inches below the lower flat. This stuffing gland had been leaking heavily due to slight bending of the propeller shaft on a previous patrol. A close depth charge detonation aft, however, fortunately caused the packing to seal tight so that no further leakage was experienced while the boat was on the bottom. Simultaneously with this close detonation, two observers claim to have seen "a ball of fire" enter through the starboard stern tube.1

(e) Into the maneuvering room through the crew's water closet when the after sanitary tank No. 3 flooded due to its sea valve opening slightly under depth charge impact.

The maneuvering room leak, item (e), would not have occurred if the head flapper valve had not been open to receive water bailed from the engine rooms. Leakage in the forward torpedo room was caused when a parted cable to the port sound head was forced up through its stuffing tube into the ship by external water pressure. This leakage was stopped by driving a wooden plug into the cable hole and securing it with clamps (Photo 5-7). The water was removed by bucket brigade to the officers' shower and by the drain pump. A further troublesome source of leakage was caused by discharge of fuel oil into the engine room upon each close depth charge detonation. Pressure built up in the collecting tank through the compensating system stand pipe and opened the inboard relief valve, thus allowing oil to enter.

5-21. The most serious leakage was that which occurred in both engine rooms when the outboard engine air induction piping flooded and water leaked by the inboard valve seats which had been slightly distorted due to pressure hull deformation. The forward engine room induction hull valve seat was forced out of round by 1/4 inch athwartships and the after engine room induction hull valve seat was forced out of round 1/4 inch fore and aft (Photo 5-15). The exact manner in which the topside induction piping became flooded is not known since a test of this system at the Navy Yard, Mare Island, disclosed no leaks and the outboard mushroom valve closed satisfactorily even though its stem was slightly bent (Photo 5-16). It is believed that the induction system probably flooded in either one or both of the following two ways: (a) fluttering of the outboard mushroom-type valve during successive close detonations, (b) temporary distortion of the main induction valve trunk while the valve was forced up during one of the detonations with subsequent eccentric seating of the valve when it came down again. This latter hypothesis might also account for the bent valve stem of the outboard induction valve. Personnel in the conning tower reported hearing air venting from the system. Leakage Into the engine rooms was controlled after 15 minutes by taking up hard on the inboard valves with chain falls (Photo 5-8). Water in the forward engine room was discharged through a hose connection to the trim line while that in


1 For further discussion see paragraph 15-18.

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the after engine room was cleared by forming a bucket brigade to the maneuvering room head in addition to using the trim and drain pumps. On later dives during the trip back to base, the induction system leaked a small amount, indicating that the induction outboard valve was not at this time seating properly. The ship's supply ventilation system piping also flooded on each dive and again no reason was evident. The hull valve for this system remained tight, however, and no inboard leakage occurred.

5-22. It was probably very fortunate for KINGFISH that the bottom was close and at only 350 foot depth, for had she been in deep water and therefore required to continue operating, the increase in weight of approximately 9 tons of water taken into the engine induction and ship's supply ventilation piping topside would almost certainly have caused her to lose depth control, as in the case of SCAMP (SS277) and SALMON (SS182). With enemy surface vessels overhead, an inadvertent rise to shallow depth or a possible broach might very well have proved fatal.

5-23. Damage to the main propulsion plant was very minor. There was some slight misalignment of the main reduction gears, resulting in an opening of .035 inches at the top of the starboard gear coupling and .030 inches at the top of the port gear coupling. Both the main motors and main reduction gears were rechocked during the subsequent overhaul. It was also discovered during the overhaul that the forward end-bells on all four main motors had been dished out such that offset oil-seal rings had to be manufactured for the forward bearings, the offset varying from 1/8 to 3/16 inches. The starboard shaft was bent approximately .180 inches but was straightened during the same overhaul without difficulty. Practically all holding down bolts and studs on the main and auxiliary machinery were stretched, although the nuts were still tight, indicating that this stretching probably was caused by excessive tightening during the original installation. There was no shearing of holding down bolts, studs or dowels. The circulating water pump attached to No. 1 service air compressor came loose due to the securing bolts backing off, but no further damage resulted. Excessive pressure on the valve disc of No. 1 outboard exhaust valve distorted both the disc itself and the seat (Photo 5-9). The disc was renewed and the seat had to be remachined. Lubricating oil piping in the maneuvering room developed serious leakage when flanges partially opened.

5-24. Damage to electrical equipment and systems was also quite minor. Direct damage was sustained by phenolic fixtures, terminal strips, contact makers, connection boxes and numerous light bulbs. Although the main control cubicle was not shock mounted, it withstood the attack with only a few small items of damage. A close depth charge detonation jarred one set of contactors open momentarily, causing considerable arcing and tip pitting, and one arcing shield fell off. This arcing might possibly explain the "ball of fire" which two observers claimed to have seen at the starboard stern tube, paragraph 5-20(d) above.

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5-25. At the time of the attack, the ship's service lighting system had been secured and the emergency system was in use. The majority of the ship's service lighting system fixtures were shock mounted by means of felt washers, but the mounting bolts were screwed down fairly tight, neutralizing the shock absorbing effect to a great extent. Bulbs screwed directly into such fixtures in general were broken throughout the ship, while those screwed into short flexible pendant cords withstood shock satisfactorily. The emergency lighting fixtures were similarly shock mounted on felt but the majority of the washers were free to absorb most of the shock and as a result, only a few of the lamps in this system were broken. A number of watertight globes in various compartments throughout the ship fractured. Overhead in the engine room, where shock was very severe, several phenolic light sockets were badly shattered (Photo 5-10). Several indicator lights burned out on the TP-TR panel as a result of the shock, although the panel, mounted on rubber pads, was otherwise undamaged.

5-26. Several micro-switches in hull opening indicators fractured (Photo 5-11), causing the TP-TR panel to record many incorrect readings. The plastic cases of these micro-switches were also broken, either by impact or due to the lever arms over-traveling. Over-travel of the contact makers was caused by slippage of the arms on their shafts since, due to an oversight, several of the arms were not pinned through to the shafts but were secured by means of nuts only. More recent type micro-switches are of the cam type, precluding this type of failure. Terminal strips in 16 contact maker aluminum connection boxes were fractured, two across the center of the strip and the rest at the ends in the vicinity of the mount screws. Failure of the strips allowed the terminals to contact the metal covers, causing short-circuits (Photo 5-12). The boxes themselves were undamaged, although they were secured directly to the hull. A metal plug in a broken receptacle above the main control cubicle dropped into the bus structure but fortunately did not cause a short circuit.1 There were approximately ten similar cases of receptacles breaking throughout the ship (Photo 5-11). Recent designs for such receptacles specify molded phenolic construction with a fabric filler and have a greater impact resistance than those installed on KINGFISH. The covers of two pressure-proof connection boxes for the external bridge reproducers were dished in and as a result, water entered the boxes, passed through the connecting cable2 and entered the 1MC amplifier assembly, disabling that system.

5-27. In general, all gauges throughout the ship withstood impact without receiving serious damage but required complete recalibration. The mounting clips broke on practically all gauges which were mounted directly to bulkheads or hull structure, leaving such gauges without any other means of support than the gauge piping, while gauges that were mounted on gauge boards, particularly electric meters, withstood the shock with very little damage. Depth gauges appeared to be among the most susceptible of all the instruments. Depth charging caused


1 See paragraph 9-29, SCAMP (SS277).
2 See paragraph 19-12 for discussion of cable end sealing.

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permanent inaccuracies of as much as 40 or 50 feet in the readings of the control room depth gauges, although they were apparently undamaged internally. The conning tower depth gauge was deranged by shock and registered a fixed reading of 28 feet. The 450-foot control room depth gauge jumped by as much as 150 feet during depth charging, the needle coming hard up against the peg. Several liquidometer gauges in the engine room and the after trim tank liquidometer were deranged due to the indicator needles jamming against the stops. Although the torpedo data computer was shock mounted on rubber, a pin in one of the shafts dropped out, rendering the after angle-solver inoperative. Both periscopes were housed during the attack. The lower prism on No. 1 periscope shattered, leaving only a small corner able to transmit an image. The upper prism on No. 2 periscope was shattered and the periscope tube flooded. No damage was sustained by the gyrocompass (Arma). The face on the pitometer log indicator in the control room shattered and the conning tower log indicator jammed when the distance counter broke free from its mounting lugs and dropped into the indicator. The rudder angle indicator system was disabled as a result of a selsyn stator winding short-circuiting (Photo 5-13).

5-28. As indicated in paragraph 5-8 above, several serious high pressure (3000-pound) air system leaks developed as a result of the attack and the large increase in pressure of the atmosphere within the boat caused much concern to personnel. No. 3 high pressure air bank in the after battery compartment lost air through a leak at one of the silver soldered "tee" connections to an air flask. This caused the loss of all air within that bank.1 Serious air leaks also developed at the cone joints of the short riser pipes connecting the high pressure air receiving and distribution manifolds. Inadequate support of these manifolds resulted in excessive movement during the attack, causing the joints to partially open. Since no stop valves were provided in these risers, it was necessary to secure the entire receiving manifold to tighten the joints. A further difficulty was encountered when it was found that the original receiving manifold had been replaced with a manifold having the riser outlets at 18-1/2 inch centers instead of the designed spacing of 19-1/2 inches, making it necessary to offset each of the short pipe connections by 1/2 inch. A considerable number


1 The internal high pressure air banks located in the forward and after battery compartments of SS212 Class Electric Boat Co. designed submarines are piped together in a common junction at the control room receiving manifold. With such an arrangement, a casualty similar to that which occurred on KINGFISH could cause the loss of all air in internal flasks. To prevent this, ShipAlt SS197 of 9 June 1943 authorised the installation of stop valves in the lines between the forward and after groups and the control manifold. The installation of a stop valve at each flask was considered but not approved due to the labor involved in installation, the difficulty of maintenance of such valves and the added number of joints in the high pressure air piping, each joint being another potential source of leakage.

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of other flanged piping and valve connections developed minor leaks as a result of the attack, principally due to holding nuts backing off under impact and allowing the joints to loosen. The most notable cases were the MBT No. 7 vent risers in the after torpedo room, various salt water lines, the hull valve on the bow buoyancy blow line, and the external flanges on the torpedo impulse air flask piping. Since air leaking from the latter flanges outside the hull released large bubbles to the surface, the impulse bottles were immediately bled down.

5-29. Numerous hull valves backed off their seats during close depth charging, allowing pressure to build up in various internal piping systems.1 After each close detonation, it was necessary to close the valves and bleed off excessive pressure in the lines. It was reported that all valves that opened had stems with Acme standard screw threads, including such valves as the torpedo tube outboard vents, sanitary tank overboard valves, inboard exhaust valves, water closet sea and stop valves, depth gauge valves, etc. Ballast tank flood and master and emergency vent valves were generally unaffected and did not leak although it was reported that the hand operating gear for most outboard valves worked more stiffly after the attack than before, apparently due to slight hull distortion. The operation of the bow buoyancy tank vent valves was considerably more difficult immediately after the attack due to slight distortion of the bow structure causing binding of the long operating shaft.2 After getting under way, operation of these valves eased up considerably. The gasket of one of the safety tank master vent valves is reported to have blown out. The ship's supply ventilation outboard mushroom valve could not be operated upon surfacing due to the backing out of a connecting pin in the operating linkage.

5-30. At the time of the attack, torpedoes were loaded in seven tubes, three forward and four aft. Muzzle doors were closed on all tubes. These torpedoes shifted under impact, bending the gyro setting spindles and causing stop bolts and guide studs to burr and wedge firmly together. One torpedo loaded aft sustained a ruptured diaphragm. Muzzle doors and shutters could not be opened immediately after the attack due to binding of the interlock mechanism. After a short time, however, the binding was no longer evident. The muzzle door gasket on tube No. 10 was damaged, allowing that tube to flood completely. Minor leakage occurred in all tubes, indicating that the muzzle doors fluttered during successive impacts. Minor damage to several breech door gaskets was also reported.

5-31. When KINGFISH was forced to the bottom, both her sound projectors were in the extended position and were bent aft. The port head was sheared off and the starboard head was badly damaged (Photo 5-14). The


1 For further discussion see paragraph 20-14.
2 ShipAlt SS330 of 7 March 1946 authorized changing the supports for the bow buoyancy tank vent valve shafting so as to connect to the pressure hull rather than the superstructure in order to eliminate casualties of this nature.

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flexible cable to the port head was parted and, as previously mentioned, this cable was forced up into the forward torpedo room, allowing water to enter. Adjacent sound equipment was thoroughly sprayed with water, grounding and disabling the entire sound system. No damage to radar or radio equipment occurred, with the exception of the parting of two topside radio antenna cables.

5-32. After receiving temporary repairs at the Submarine Base, Pearl Harbor, KINGFISH proceeded to the Navy Yard, Mare Island, arriving on 20 April 1943. Complete battle damage repairs, regular overhaul and numerous outstanding alterations were accomplished there and KINGFISH was returned to service on 16 June 1943.

5-33. The experience of KINGFISH indicates that at this period of the war a creditable balance between strength of hull structure and damage resistance of vital machinery and systems had been achieved on SS212 Class submarines. Although she was subjected to depth charge detonations along her entire length close enough to cause considerable permanent pressure hull deformation in several areas, KINGFISH remained fully operational in both submerged and surfaced conditions and her torpedo offensive power could have been almost wholly restored by repairs within the capacity of the ship's force.

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Photo 5-1: KINGFISH (SS234). Section of damaged pressure hull plating removed between frames 79-85 over the forward engine room. Note maximum indentation of 1-1/4 inches between frames 82-83. Riveted plate edge shown here is forward transverse butt of forward engine room hard patch.

Photo 5-2: KINGFISH (SS234). View showing distortion at starboard riveted joint of keystone frame 85, in way of riveted hard patch over forward engine room.

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Photo 5-3: KINGFISH (SS234). View showing distortion of frame 83 and depressions in pressure hull plating between frames 82-84, over forward engine room.

Photo 5-4: KINGFISH (SS234). View showing depressions in shell plating, port side, frames 103-108, in way of lubricating oil tanks. Damage on starboard side was similar.

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Photo 5-5: KINGFISH (SS234). View showing conning tower after bulkhead, indicating points at which W.T. door dogs bound due to distortion of bulkhead and door seat.

Photo 5-6: KINGFISH (SS234). View showing distortion to cover of 20mm ready service ammunition stowage located on the after bridge deck. This stowage flooded.

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Photo 5-7: KINGFISH (SS234). View showing parted cable to port JK-QC sonar projector and the improvised plugging arrangement for the cable stuffing tube.

Photo 5-8: KINGFISH (SS234). View showing chain fall rig used for securing leakage around air induction hull flapper valve at frame 92-1/2 in the after engine room. Valve seat was slightly distorted by adjacent pressure hull deformation. (See Photo 5-15).

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Photo 5-9: KINGFISH (SS234). View showing distortion which occurred to the No. 1 engine outboard exhaust valve disc.

Photo 5-10: KINGFISH (SS234). View showing typical damage to phenolic light sockets in overhead of engine rooms.

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Photo 5-11: KINGFISH (SS234). View showing typical examples of damage which occurred to micro-switches and receptacle covers.

Photo 5-12: KINGFISH (SS234). View showing damage to terminal strips in connection boxes which allowed the terminals to fall against the box and cause short-circuits.

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Photo 5-13: KINGFISH (SS234). Shorted selsyn transmitter stator which disabled the rudder angle indicator system.

Photo 5-14: KINGFISH (SS234). Grounding damage to starboard QB sonar projector. Both the port and starboard projectors were in extended position when the boat was forced to the bottom.

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Photo 5-15: KINGFISH (SS234). View showing distortion of seat for after engine room air induction hull valve at frame 92-1/2. Leakage around this valve flooded after engine room to level of lower floor plates. (See Photo 5-8).

Photo 5-16: KINGFISH (SS234). View showing distortion of engine air induction outboard mushroom valve due to bent valve stem. Valve is reported to have seated tightly when tested at Navy Yard, Mare Island.

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Plate V: Depth Charge Damage


SECTION VI

U.S.S. TUNNY (SS282)

Depth Charge Damage Forward

Off Palau Islands

26 August 1943

Class

SS212

Builder

U.S. Navy Yard, Mare Island

Commissioned

1 September 1942

Length (Overall)

311 ft. 8 in.

Beam (Extreme)

27 ft. 3-1/4 in.

Submergence Depth (Designed Maximum) (Axis)

300 ft.

Displacements

Standard

1525 tons

Emergency Driving Trim

1946 tons

Submerged

2410 tons

Draft (Mean, Emergency Diving Trim)

16 ft. 2 in.

Type of Propulsion

Diesel Electric Reduction Drive

Main Engines (4)

Fairbanks-Morse 38-D-8-1/8

Main Motors (4) and Generators (4)

General Electric Co.

References:

(a) C.O. TUNNY conf. ltr. SS282/A16-3/A9, Serial No. C-16 of 8 September 1943 (Report of War Patrol Number Four).
(b) C.O. TUNNY conf. ltr. SS282/S9, Serial No. C-18 of 15 September 1943 (Report of War Damage).
(c) OinC U.S. Naval Drydocks, Hunter's Point conf. ltr. SS282/L11-1 (06566); (308) of 8 March 1944 (Supplementary Report on TUNNY War Damage).

Photographs Nos. 6-1 through 6-7 (furnished by C.O. TUNNY, Naval Drydocks, Hunter's Point, and Bureau of Ships)

PLATE VI

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6-1. On 26 August 1943, during her fourth war patrol, TUNNY underwent a severe depth charge attack off the Palau Islands. Two charges detonated close aboard the bow while the ship was submerged to a depth of 300 feet, causing extensive structural damage to the single hull plating and framing in way of the forward torpedo room and considerable other damage throughout the boat. Although depth control was temporarily lost, due to jammed bow planes and brief cutoff of main power, TUNNY was able to remain submerged and make good her escape. This report is based on the information contained in the references and on informal interviews with various officers attached to TUNNY. The Photographs were furnished by C.O. TUNNY, U.S. Naval Drydocks, Hunter's Point, and this Bureau. The PLATE was prepared by the Bureau and the structural indentations noted thereon are based on data contained in the enclosures to reference (c).

6-2. TUNNY arrived at the Submarine Base, Pearl Harbor, on 14 July 1943 from her third war patrol. Following normal refit and training, she departed Pearl Harbor for Midway on 5 August and arrived on 9 August. Here minor voyage repairs were made and fuel and lubricating oil were topped off. On 10 August TUNNY departed Midway for her fourth war patrol and on 22 August reached her assigned patrol area in the waters adjacent to the Palau Islands.

6-3. On 25 August TUNNY damaged two medium-sized freighters out of a six-ship Japanese convoy by one torpedo hit each during a pre-dawn submerged attack. Further attacks against this convoy were terminated when TUNNY was forced to take evasive action by an enemy destroyer escort. After the escort had retired and the safety of darkness permitted, TUNNY surfaced and remained on the surface until near dawn on 26 August, submerging again at 0412.

6-4. At 0959, 26 August 1943, while still submerged, periscope contact was established with two medium-sized Japanese freighters approaching from the south, escorted by one aircraft (DAVE) and one PC type surface vessel. TUNNY was at this time in a position off Toagel Mlungui Pass about 3,000 yards outside the reef to westward of Babelthuap Island, lat. 7° 30' N., long. 134° 20' E. At 1037, after closing to make a submerged periscope attack and with the enemy PC only 400 yards off her starboard beam, TUNNY fired a spread of three torpedoes at the leading freighter from a range of 980 yards and two torpedoes at the second freighter from a range of 1260 yards. As the last torpedo was fired, TUNNY headed for 300 foot depth at full speed, rigged ship for silent running and depth charge attack, and commenced evasive action. On the way down, two hits on the first freighter were heard. The propellers of this ship stopped and were not heard again. The second freighter turned toward TUNNY, successfully avoiding both torpedoes, and passed directly overhead.

6-5. At 1058, 20 minutes after the attack, either the enemy PC or DAVE located TUNNY and dropped two depth charges or depth bombs. These detonated well above the ship and did no damage. Two minutes

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later, at 1100, six depth charges were dropped by the PC in close pattern around TUNNY and in rapid succession, detonating a few seconds apart. The first two charges detonated fairly close over the after portion of the ship but caused no damage, with the possible exception of that which occurred to the control cubicle in the maneuvering room. The second two charges detonated amidships above the conning tower and, although closer, caused no structural damage and probably little, if any, shock damage. The last two charges detonated close to the bow, causing extensive structural deformation forward and considerable damage to fittings and equipment throughout the boat. After this attack, no more depth charges were dropped, although the enemy vessel remained in TUNNY's immediate vicinity for several hours.

6-6. From the location and degree of deformation which occurred to the forward pressure hull structure, it appears that the last two depth charges detonated port and starboard abreast the forward trim tank at or just below the level of the pressure hull axis. All six charges were probably of the Japanese Type 95, Mod. 2 design, containing 242 pounds Type 1 explosive, and were probably set by pairs for detonation at 98, 197 and 292 feet. Since TUNNY was submerged to a depth of 300 feet, the setting of 292 feet, which was the maximum setting possible with the Type 95 depth charge pistol, would have resulted in detonation at the proper depth to correspond with the damage which actually did occur. Based on known behavior of similar type structures when subjected to underwater explosions, it is estimated that both charges detonated about 50 feet from the hull.

6-7. The depth charge attack had immediate serious effects on TUNNY, (a) Personnel forward were thrown from their feet and loose gear was hurled about, (b) Propulsion power was temporarily cut off by ship's force due to a fire in the main control cubicle which started when the positive and negative main battery busses jarred together momentarily, (c) Shortly afterwards, auxiliary power was also lost throughout the boat for several minutes when the auxiliary circuit breaker aft opened. The exact reason for this casualty is not known, but was reported by the Commanding Officer to have been due to maloperation of the auxiliary switchboard by personnel rather than material failure due to depth charging. This naturally added somewhat to the tendency for confusion which exists after any severe attack, (d) The bow planes jammed on 9 degrees dive angle due to misalignment and binding in the operating gear caused by distortion of supporting structure, (e) The upward water thrust from the depth charge detonations under the bow and the downward thrust from the detonations over the stern immediately caused the ship to assume a 20 degree up angle. Men were sent forward quickly in an effort to reduce this angle. The ship climbed to 200 feet but the angle on the boat then reversed, due to the bow planes being jammed in dive position and the added weight of the men sent forward. The ascent was followed by a steep glide to about 380 feet. Depth control was finally regained several minutes later, after much porpoising, by shifting from hand to power operation of the stern planes when auxiliary power again became available. The bow planes were then forced back to 5 degrees dive angle by using emergency hydraulic power; i.e., taking oil directly from the main hydraulic plant. However, the planes could not be tilted below 5 degrees by either hand or power operation. The damage control parties functioned coolly and efficiently throughout this period, restoring order and almost normal conditions within five minutes after the attack.

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6-8. That TUNNY neither broached nor went excessively deep after depth control was lost was attributed by the Commanding Officer in large measure to the fact that the boat was fortunately operating at this time in a pronounced negative temperature gradient. This caused the boat to become heavy overall as it ascended and light overall as it descended.1 The effect was sufficient to keep TUNNY oscillating within the water strata below 200 foot depth and above 380 foot depth.

6-9. After regaining propulsion power, TUNNY retired to the southwest at two-thirds speed, running at 360 foot depth and under the sonar protection of the temperature gradient. The enemy PC passed overhead once more but did not attack, either having no depth charges left or not detecting TUNNY's presence. At 1625, TUNNY commenced operating at periscope depth and secured from silent running. At 1858 she surfaced and proceeded to clear the area rapidly.

6-10. At this time it was felt that perhaps sufficient repairs could be effected to enable TUNNY to remain on patrol. Inspection of the topside revealed that the bow had received considerable damage. Numerous pieces of torn and twisted metal from the cases of the depth charges, about 15 pounds in all, were found scattered over the superstructure deck forward of the capstan. The bow buoyancy tank vent valve operating gear had jammed with the forward vent in closed position and the after vent only partially opened. In order that the boat might again dive, a permanent vent opening was made in the bow buoyancy tank top by removing the manhole access plate. By slacking off on the bow plane tilting shaft packing glands and applying liberal amounts of grease to the bushings, the planes were finally jacked back to zero tilt from within the boat and rigged in.2 Work was started at once on the stern torpedo tubes, where it was discovered that all four gyro spindles had been bent and could not be withdrawn. All hands were kept busy restoring order and attempting repairs to deranged equipment.

6-11. By midnight of 28 August, everything within the power of the ship's force to put the ship in normal operating condition had been accomplished, but the following unsatisfactory conditions remained:

(a) Bow planes still could not be tilted either in hand or power operation, making depth control near the surface somewhat erratic.


1 For each degree F. change in sea water temperature in the vicinity of 70° F., assuming average salinity content and near surface conditions, the change in buoyancy of an SS212 Class will be of the order of 825 pounds.
2 A modification to permit rigging bow planes over a wide tilt angle range of from 0° to 15° dive was authorized for SS198 and subsequent submarines by BuShips ltr. SS/S22(515-815) of 24 November 1944. Had this alteration been accomplished on TUNNY at this time, the bow planes could have been rigged in immediately, even though jammed on 5° dive.

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(b) Bow buoyancy tank was unusable as such.

(c) Considerable air leakage through the 600-pound blow manifold for the forward group of main ballast tanks made it necessary to secure the individual tank hull regulator stop valves when submerged (this condition was present before depth charging).

(d) No. 2 low pressure blower was out of commission due to a short-circuited shunt field.

(e) The optics of No. 2 periscope were deranged, reducing light transmission by 25 per cent.

(f) The IMC system on the bridge and in the conning tower was irreparably damaged.

(g) Two of the remaining eight torpedoes required a major overhaul.

(h) All forward torpedo tubes were out of line and out of round, preventing firing of torpedoes from these tubes.

(i) The JK-QC sound projector could not be trained.

6-12. Since the above conditions rendered TUNNY's offensive power negligible, it was decided to return to base for repairs and make her very active area available to another submarine. Therefore, at 0013 on 29 August, TUNNY departed for Pearl Harbor. The return trip was made entirely on the surface except for occasional dives when enemy or unidentified aircraft were sighted. Diving time without the aid of the bow planes was 60 to 75 seconds, somewhat slower than the normal time of about 45 seconds. TUNNY arrived at Submarine Base, Pearl Harbor on 8 September.

6-13. Structural damage was confined to the ship forward of frame 31. Damage to the elliptically shaped single pressure hull in this region consisted of minor distortion of the framing with marked general depressions of the shell plating between frames (PLATE VI, Photos 6-1 through 6-5). Transverse bulkheads at frames 10, 13 and 16 were slightly buckled. Bow buoyancy tank frames and plating were dished inward (Photo 6-6) and the superstructure deck plating was slightly buckled. Examination of the vessel revealed that the entire forward section had been displaced to starboard. This deflection increased from 1/8 inch at frame 37 (forward knuckle) to 1 inch at the bullnose. There was local bending of the stem bar to port between frames A and B, the maximum displacement amounting to about 2 inches at the 20-foot waterline (Photo 6-6). The bullnose was found to have moved upward 1/2 inch relative to the base line.

6-14. Deformation of the pressure hull plating was about equally distributed port and starboard (Photos 6-1 and 6-4). The maximum plating indentation on the starboard side was 2-1/16 inches in way of the forward trim tank between frames 13 and 14 at about the 14-foot waterline. General dishing of plating on the starboard side extended aft to frame 25 and was

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concentrated between the 10-foot and 14-foot waterlines, depths of indentation averaging between 1 and 1-1/2 inches. Damage to the port side pressure hull plating was similar to the starboard side in nature and location, although it did not include as large an area. Minor isolated dents, not shown on PLATE VI, occurred both port and starboard.

6-15. The bossing for the bow plane tilting shaft sector gear, built into the overhead of the pressure hull between frames 16 and 17, was depressed both port and starboard to a depth of about 2 inches (Photo 6-5). Since no other pressure hull plating in this vicinity was affected, it was apparent that a structural weakness existed in the design of the bossed area. Another region of local failure was the section of the hull plating between the escape trunk and the torpedo loading hatch, which was depressed to a depth of about 1 inch over a distance of about four feet on either side of the centerline. However, no difficulty was encountered in removing the transverse compression strut in the torpedo loading hatch after the damage, demonstrating that the hull distortion was not sufficient to jam the strut threads.

6-16. All welded seams and butts in the pressure hull remained tight, even though some were severely distorted. Welds joining framing to plating were also undamaged. There was no leakage into the boat which could be attributed to depth charge damage.

6-17. Pressure hull frames 13 to 30 were found to deviate slightly from their designed offsets, maximum variation occurring in way of the forward trim tank and forward portion of the torpedo room. Considered as a whole, the starboard framing presented a fair surface although actually deflected outboard by amounts from as high as 3/4 inch to an average of only 1/4 inch. Maximum deflections occurred in the vicinity of the 5-foot waterline. There were no local depressions in any frames. Portside framing was, in general, pushed inboard, but deflections were less than on the starboard side. There was, however, some unfairness of framing. Maximum frame deformations on the port side occurred in the vicinity of the 13-foot waterline but varied from designed offsets by only 1/8 to 1/4 inch. These latter variations are insignificant and may well have occurred during construction of the vessel. PLATE VI illustrates the relative distortion of the pressure hull ellipse from the designed dimensions.

6-18. Bulkhead 10, the after bulkhead of the bow buoyancy tank, sustained only minor distortion but this was sufficient to jam the operating shaft for the bow buoyancy vent valves. Bulkhead 13, the forward bulkhead of the forward trim tank, was generally depressed aft between the torpedo tubes and the shell, port and starboard, with a maximum deflection of about 3/4 inch. This bulkhead leaked slightly around the tubes, allowing a small amount of water to enter the trim tank when submerged. Bulkhead 16, the after bulkhead of the forward trim tank, sustained only minor distortion but did move slightly relative to the torpedo tubes. This was evidenced by bright metal showing on the

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tube collar shoulders, but the motion was not sufficient to shear the fiat head screws securing the bulkhead collars to the tubes nor did any leakage into the boat occur.

6-19. Superstructure and bow buoyancy tank damage was minor. The side plating of the bow buoyancy tank was depressed between frames forward of frame 0, principally on the starboard side (Photo 6-6). The rolled deck gunwale plates, both port and starboard, were severely buckled between frames 17 and 18, indicating that the bow had been whipped upwards by one of the close detonations, putting the deck in compression in the region of the buckles. The deck plating forming the top of the bow buoyancy tank was cracked in one place only. This occurred as a result of a stiffener on bulkhead 10 pulling away from the underside of the deck.

6-20. One of the most serious results of the depth charge attack was the damage which disabled the bow plane tilting gear. The principal cause of this derangement was binding due to misalignment of the main herringbone pinion and the sector gear on the bow plane shaft, caused by the deflection of the forward trim tank bulkhead at frame 16 upon which this gear assembly was mounted. Secondary binding of the tilting shaft also occurred port and starboard at the pressure hull stuffing boxes and was caused by distortion of the elliptical hull. The bow plane rigging mechanism remained completely operable, although some misalignment of the transmission shafting was discovered afterwards when disassembling the equipment.

6-21. The only casualty which occurred to the main propulsion plant and associated systems and auxiliaries was the control cubicle derangement previously mentioned. Although the control cubicle was not shock-mounted, it withstood impact without damage to contactor groups or mechanical equipment. However, the positive and negative main battery busses in the forward contactor cell were momentarily thrown together, causing a small fire and considerable pitting of the busses (Photo 6-7).1 Simultaneously, the battery selector lever jumped from the "Both Batteries" position to the "Forward Battery" position. The main motors were stopped for about one or two minutes to extinguish the fire and then were started again on the forward battery only. Damage resulting from the fire was negligible, but dense toxic smoke given off by burning glyptol insulating varnish on the bus bars made inspection of the cubicle difficult and forced several men to abandon the maneuvering room.

6-22. The lighting systems were not appreciably damaged, with the exception of numerous broken bulbs and a resistor in the forward engine room emergency lighting circuit which short-circuited and caused a full voltage ground across the forward battery. Since the boat was rigged for silent running, only the emergency lighting system was on at the time


1 As a result of this casualty, the installation of phenolic insulation between the propulsion control cubicle main battery busses to prevent short-circuiting under shock was authorized by ShipAlt SS222 of 6 December 1943 for TUNNY and all other applicable submarines.

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of the attack. Numerous gauges and meters were thrown out of calibration and a few sustained damage. Several thermometers in the engine rooms were broken. The shock effect was widespread throughout the boat and there was no apparent concentration in any one locality.

6-23. During the attack mercury spilled from the float chambers of both the master and auxiliary gyro compasses, putting them out of commission and necessitating dismantling for cleaning and readjustment. The glass cover of the gyro repeater on the bridge was broken and the instrument flooded. After the casualty occurred to the gyro compasses, the ship was steered by magnetic compass. The fact that the battery selector lever in the control stand had moved from the "Both Batteries" position to the "Forward Battery" was not discovered until about ten minutes after the attack occurred when it was noted that both magnetic compasses (tank type and boat) were behaving erratically. This was due to the fact that the compasses had been compensated a few days previously for the magnetic conditions present with the ship taking propulsion power from both the forward and after batteries. Drawing power from only the forward battery set up an unbalanced magnetic field of sufficient intensity to produce a deviation of as much as 30° .

6-24. The upper prisms of both periscopes were cracked. The power field of No. 2 periscope was out of focus and light transmission reduced by 25 per cent. Nitrogen pressure was lost in No. 2 periscope but the periscope was recharged to eight pounds.

6-25. There was only one major piping leak which developed as a result of the attack. This occurred at the high pressure air (3000-pound) receiving and distribution manifolds in the control room and caused great concern to all hands. The manifold assembly was installed in such a manner that it was supported principally by the piping leading to it, permitting large deflections under impact. The cone joint at the connection of the after high pressure air riser to the distribution manifold opened sufficiently to permit serious leakage but fortunately did not carry away completely.1 Air pressure within the boat increased appreciably but the amount could not be measured since all barometers and manometers were damaged. Although there was considerable structural damage in way of the forward torpedo air impulse flasks, located outside the pressure hull, the flanged joints of the impulse piping both at the flasks and pressure hull remained tight and the banks did not bleed down. As previously mentioned, a valve leak in the 600-pound blow manifold supplying the lines leading to the forward group of ballast tanks necessitated securing the individual tank hull stop valves to prevent air from forming bubbles in those tanks. This leak was present before the attack but was aggravated by the depth charge detonations. Hydraulic lines and fittings generally remained tight


1 As a result of this casualty on TUNNY, and the similar experience of KINGFISH (SS234) on 23 March 1943, ComSubPac conf. ltr. FF12-10/S49/L11-1/70 of 20 November 1943 directed that the high pressure air receiving and distribution manifolds be rigidly bracketed together and to the hull on all submarines where existing support was not sufficiently rigid. NYMI Plan No. 65557 was developed as a typical bracketing arrangement.

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except for several serious leaks in the control room. Numerous valves throughout the ship, regardless of location, partially opened under impact, the discs backing off the seats. Both the forward and after 225-pound service air lines had to be secured at the manifold until damage control personnel could check and reclose the valves in that system. For example, the 225-pound air valve to the conning tower1 opened on each of several close detonations and was closed on each occasion by the Commanding Officer himself. Trim line strainers were partially clogged in the variable tanks when depth charging caused flaking of the plastic composition with which those tanks were coated.2 All vent and flood valves were undamaged with the exception of the bow buoyancy vent valves, previously mentioned.

6-26. Both the SD and SJ radars were deranged by the impact of the depth charges, the SJ becoming inoperable. On the SJ, the cathode ray tube was damaged internally so that the registered sweep was only 2 inches wide, the magnetron tube failed, the triode tube jarred out of its socket and the bearing indicator slipped 10 degrees out of phase. The SD radar withstood the impact somewhat better. It could be made to pulse but was also badly out of adjustment and it was found necessary to renew thirteen tubes shortly after the attack, indicating that they were considerably affected by the impact. No damage to radio equipment occurred. There was no damage to the electronic portion of the sonar equipment but the drift stops on the port JK-QC sound projector crushed under impact, preventing it from training, and the starboard QB head was slightly dented. Both heads were operable electronically after the attack.

6-27. All forward torpedo tubes were found to be both out of line and out of round. The deviation in alignment was fairly uniform and was apparently due only to the displacement of the entire bow structure to starboard. The azimuth error varied from 13 minutes starboard on tube No. 1 to 15 minutes starboard on tube No. 6. In addition, all forward tubes were slightly bent along their longitudinal axis, the maximum deviation being 0.110 inches on tube No. 5. The bending occurred at the junction of the breech section of the tubes with the middle section, at the forward trim tank bulkhead. The monel screws securing these sections apparently loosened somewhat, for it was reported that the sealing compound around the screws backed out and slight leakage occurred into the tubes. The circular distortion of the tubes was such that it was found impossible to start a bore gauge in any of them, tube No. 6 being out of round by as much as .210 inches. The outer doors, shatters and operating gear on all tubes remained workable in spite of


1 The 225-pound blow line to conning towers was later removed on all submarines when that compartment was disestablished as an escape station.
2 Due to its tendency to flake, this white plastic composition, formula 89 (Barrierkote) was subsequently removed from all submarine variable tanks and replaced with rust preventative compound (N.D. Spec. 52C18, Grade III).

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the distortion to the intervening bulkheads. Tubes Nos. 1 and 4 were reported by reference (a) to have flooded as a result of the attack, the muzzle door gaskets presumably sustaining some damage. No misalignment or distortion occurred to the after tube nest. However, the after tubes were loaded and flooded at the time of the attack and movement of the torpedoes under impact within the tubes bent the gyro setting spindles and guide sleeves so that the spindles could not be withdrawn. All torpedoes were removed for checking and the spindle assemblies were replaced by the ship's force, using the one available spare and three taken from forward tubes. The stop bolt in No. 10 torpedo tube was also found to have been bent and this was replaced. Two torpedoes were so shaken up internally that they required a major overhaul beyond the capacity of ship's force. The other six were thoroughly checked and considered satisfactory.

6-28. Upon arrival at the Submarine Base, Pearl Harbor, TUNNY was immediately docked in the ARD-1 to investigate the extent of structural damage. She departed Pearl Harbor on 11 September 1943 and arrived at U.S. Naval Drydocks, Hunter's Point, on 17 September. Complete damage repairs, regular overhaul and the majority of the outstanding alterations were accomplished there. The entire forward torpedo tube nest was removed from the ship and repairs were made to the individual tubes prior to reinstallation. Renewal of the forward pressure hull structure was accomplished as indicated by the outlines on PLATE VI. TUNNY was returned to active service on 2 January 1944.

6-29. As a matter of interest, TUNNY was twice more seriously damaged by bomb attack on subsequent patrols, the first action occurring on 30 March 1944 during her fifth patrol and the second action occurring on 1 September 1944 during her seventh patrol.1 On both occasions the bombs detonated in close proximity to the maneuvering room. In the first instance, control cubicle damage was again sustained although the cubicle was shock-mounted during the overhaul completed just prior to the patrol. It is understood, however, that later examination disclosed that one of the cubicle transverse support frames was improperly placed so that it was in direct contact with the cubicle cage, thus nullifying the effect of the rubber mounting. This condition was corrected and it is significant to note that although in the subsequent action of 1 September 1944 the bomb detonated close enough to permanently deform several areas of the pressure hull in way of the maneuvering room, no damage was sustained by the control cubicle.


1 See briefs of damage in Appendix I for these two subsequent actions.

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Photo 6-1: TUNNY (SS232). General view of starboard side forward showing deformation in way of single hull and forward trim tank.

Photo 6-2: TUNNY (SS282). Close view, looking up, showing depressions in pressure hull plating between frames, starboard side.

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Photo 6-3: TUNNY (SS282). Close view showing depressions in pressure hull plating between frames, starboard side. Note the 45° diagonal pattern of the bulges.

Photo 6-4; TUNNY (SS282). General view of port side, forward, showing deformation in way of single hull and forward trim tank.

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Photo 6-5: TUNNY (SS282). View of local depression in pressure hull between frames 16 and 17, in way of boss for bow plane tilting shaft sector gear. Photo taken inside superstructure and looking to starboard. Similar depression occurred in port side.

Photo 6-6: TUNNY (SS282). View showing deformation of bow buoyancy tank structure. Note bent stem at 20-foot W.L.

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Photo 6-7: TUNNY (SS282). View showing after side of forward contactor group on General Electric propulsion control cubicle. Arcing occurred on the forward side of the designated bus bar when the positive and negative main battery busses were momentarily thrown together (paragraph 6-21).

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Plate VI: Depth Charge Damage


SECTION VII

U.S.S. SALMON (SS182)

Depth Charge Damage

Southeast of Kyushu

30 October 1944

Class

SS182

Builder

Electric Boat Co., Groton, Conn.

Commissioned

15 March 1938

Length (Overall)

308 ft. 0 in.

Beam (Extreme)

26 ft. 2 in.

Submergence Depth (Designed Maximum)(Axis)

250 ft.

Displacements

Standard

1435 tons

Emergency Diving Trim

1885 tons

Submerged

2210 tons

Draft (Mean, Emergency Diving Trim) ...

17 ft. 6 in.

Type of Propulsion

Composite

Main Engines (4)

General Motors 16-278A

Main Motors (4) and Generators (2)

Elliott Co.

References:

(a) C.O. SALMON conf. ltr. SS182/A9/A-16-3, Serial No. 0-16 of 10 November 1944 (Report of War Patrol Number Eleven).
(b) C.O. SALMON conf. ltr. SS182/A9-8, Serial No. 024 of 11 December 1944 (War Damage Report).
(c) OinC U. S. Naval Drydocks, Hunter's Point conf. ltr. SS182/L11-1(012459)(308) of 29 March 1944 (Supplementary War Damage Report).
(d) U.S. Navy Board of Inspection and Survey ltr. SS182/S3-1 (5000-S), Serial No. 271121 of 18 December 1944.

Photographs Nos. 7-1 through 7-13 (furnished by Naval Drydocks, Hunter's Point).

PLATE VII

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7-1. On 30 October 1944 during her eleventh war patrol, SALMON underwent a severe depth charge attack southeast of Kyushu while submerged at a depth of about 300 feet. As a result of this attack, SALMON incurred severe damage. This case of damage can be considered one of the most serious to have been survived by any U.S. submarine during World War II. Pressure hull deformation was extensive in way of both engine rooms. The external main engine air induction piping collapsed and flooded, causing the ship to become heavy overall, and the stern diving planes jammed in "full dive" position. Depth control was immediately lost and SALMON oscillated up and down several times, remaining submerged only by blowing the safety tank and by going ahead at emergency speed with a 20 degree up angle on the boat. Seventeen minutes after the attack, with batteries depleted, the after engine room flooded almost to the level of the main motors, and still not having achieved depth control, SALMON surfaced, outgunned the opposing Japanese escorts and escaped with three engines on full power. This report is based on the information contained in the references and on further informal correspondence with the then Commanding Officer. The Photographs were furnished by Naval Drydocks, Hunter's Point. The PLATE was prepared by this Bureau.

7-2. Upon completion of her tenth war patrol, SALMON underwent an extensive overhaul at Navy Yard, Mare Island. During this period the four Hoover, Owens and Renschler main Diesel engines were replaced by General Motors Model 16-278A engines and all of a long list of important outstanding alterations were accomplished.

7-3. SALMON completed overhaul and departed from Navy Yard, Mare Island for the Submarine Base, Pearl Harbor on 4 September 1944, arriving on 12 September. From 12 September to 17 September, voyage repairs were made at the Submarine Base and from 17 September to 21 September training exercises were conducted in the Hawaiian area. SALMON departed from Pearl Harbor on 24 September and arrived in Tanapag Harbor, Saipan, on 3 October. There minor voyage repairs were again made and fuel and lubricating oil were topped off.

7-4. SALMON departed Saipan on 4 October for her eleventh war patrol in company with SILVERSIDES (SS236) and TRIGGER (SS237), forming a coordinated attack group. Her assigned patrol area was along the eastern boundary of the Nansei Shoto Islands on the southern approaches to the Japanese home islands. Although independent searches were conducted over a wide area by the group, and numerous harbors were reconnoitred, no suitable targets were sighted until 30 October.

7-5. At 0401 on 30 October 1944, SALMON established radar contact with a large Japanese tanker escorted by four frigate class vessels, radioed a contact report giving the position, course and speed of the target, and then commenced surface chase. Chase was long and difficult

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due to the high speed of the tanker, its radical course changes, and occasional rain squalls during which contact was lost for short periods. At 1620, SALMON noted a large explosion in the target's stern (result of TRIGGER attack) and the tanker appeared to stop shortly afterwards. Anti-submarine activity by the escorts started at once and many depth charge explosions were heard through the hull during the next half hour.

7-6. At 1740, SALMON started closing the range for an attack. The enemy tanker was at this time immobilized about 24,000 yards distant, bearing 170° (T) and drifting with the wind in a southwesterly direction at a speed of about one and one-half knots. The four Japanese escorts were patrolling slowly back and forth about 1200 yards on both sides of the tanker. SALMON'S position was lat. 30° 08' N., long. 132° 33' E., about 120 miles southeast of Kyushu. The sea was moderate and the wind was Beaufort force 3 to 4. At 1823, upon closing the range to about 8000 yards, SALMON submerged and commenced attack approach. Her main shafts were squealing badly, a condition which had developed during the preceding few days and was steadily getting worse. At 2001, at an estimated range to the target of 3,300 yards, a spread of four torpedoes was fired, two of which struck and detonated in the target.1

7-7. At the time of firing, SALMON was on course 215 degrees and at periscope depth of 64 feet. The long firing range was accepted because three of the enemy escorts were approaching rapidly and it was feared that no further decrease in range could be made without detection. Immediately after firing, SALMON swung right, using full rudder, in order to bring her stern tubes to bear for another salvo should it become necessary. However, three of the four torpedoes of the initial salvo were seen to broach and either this evidence of SALMON'S presence or positive detection by sonar caused two of the escorts to head directly toward her almost simultaneously from each quarter so, at 2012, SALMON went deep. As the boat submerged, speed was increased to standard and the rudder was put in full left position. One minute later, at 2013, when a depth of 310 feet had been reached, a series of small "sono-bomb" explosions were heard.2 These were followed almost immediately by the first of four close and well delivered depth charge patterns.


1 Although TRIGGER (SS237) and SALMON each made torpedo hits on this tanker, it remained afloat and was later sunk by STERLET (SS392). SALMON was officially credited with a "sunk" tonnage of 3,300 tons, equal to one-third the total estimated tonnage of the tamper.
2 These "sono-bomb" explosions may have been either "Emit Sound Missiles", known to have been frequently used by the Japanese just prior to commencing a depth charge attack, or the detonations of projector charges in depth charge throwers on the escorts (See paragraph 3-19).

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7-8. A total of about thirty depth charges were dropped, each of the four separate patterns consisting of from six to eight charges. The first and second patterns were received almost simultaneously and one or more of these charges detonated very close aboard over the engine rooms, causing the collapse and flooding of the engine air induction piping and possibly some or all of the pressure hull deformation between the tank tops over the engine rooms. The final two patterns followed a short time later but were not close enough to have serious effects although the boat was shaken up considerably. All of the thirty or so depth charges detonated aft in so far as could be determined on SALMON. The Commanding Officer reported that severe flexural vibrations of the ship as a whole occurred during close detonations, stating that "The conning tower vibrated up and down so violently that I thought the ship was going to shake herself apart. I remember bending my knees to ease the shock". Damage to the ship was severe and widespread. Unattached gear and many inadequately secured small fixtures were hurled about during close detonations and presented an appreciable missile hazard to personnel in some areas.

7-9. The most serious immediate effect of the attack was that depth control was lost. The boat became heavy overall and started to settle rapidly. Several factors contributed to this dangerous situation: (a) loss of buoyancy due to collapse and flooding of the external main engine air induction piping; (b) added weight due to flooding of three deck access hatch trunks, profuse leakage of sea water into the interior of the hull at various points and the displacement of about 7,000 gallons of fuel oil in FBT No. 7 with heavier sea water through the ruptured vent riser of that tank; (c) jamming of the stern planes in "hard dive" position due to binding of the stern plane hand tilting shafting in the after engine room by a local indentation of the pressure hull and shattering of the stern plane drive shaft coupling in the after torpedo room; and (d) the downward flow of water from the overhead depth charge detonations.

7-10. Submerged propulsion power was unaffected and was a vital factor in the survival of the boat. Auxiliary power forward was temporarily lost when shock caused the auxiliary power circuit breaker in the after engine room to trip. However, the breaker was reset by hand shortly after it opened and auxiliary power was restored throughout the boat. No. 1 lighting motor generator voltage regulator control was damaged and, since this generator was supplying the standard lighting load, all ship's service lighting failed and the ship was plunged in darkness. The emergency lighting system was switched on immediately, however, and operated satisfactorily although numerous light bulbs throughout the boat were broken. Various IC and auxiliary motor controller panel contactors opened under shock and had to be reset by hand.

7-11. Only one serious air system leak developed, this occurring in the forward engine room at a joint in No. 1 main engine air starting line (500-pound). Numerous minor air leaks developed throughout the boat. Power steering control was lost due to disconnection by shock of the supply piping to the steering hydraulic manifold in the after torpedo room. Steering control was not regained until about five minutes later when a shift was made to hand operation.

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7-12. The most serious leakage into the hull was that which occurred in both engine rooms through the fuel ballast tank riser inboard vent lines, the stop valves having torn from their holding studs. The sea water streams resulting at these points were small in cross section but fast, and rapidly filled the bilges. The drain line suction strainers in the engine rooms were clogged with debris rendering it impossible to pump the water flooding into those two compartments. The water level eventually neared the main motors and was one of several reasons which soon forced SALMON to surface. Serious leakage also occurred in the conning tower as described in paragraphs 7-23 and 7-25.

7-13. When it was first noticed that SALMON was increasing depth rapidly, emergency speed ahead was rung up, a 20 degree up angle was set on the boat with the bow planes and the auxiliary tanks were pumped. These measures served to check the descent at about 400 feet depth. The boat then rose to about 300 feet but when an attempt was made to level off and reduce speed to standard, SALMON again settled rapidly. Emergency speed ahead and a 20 degree up angle on the boat were once again resorted to and in addition the safety tank was blown, but this time the descent was not halted until a depth of about 500 feet had been reached. Once more the boat started to rise and reached 150 feet depth but started to drop again when another attempt was made to level off. This time SALMON went quite quickly to about 500 feet depth, in spite of again using emergency speed ahead and a 20 degree up angle, and then gradually settled to a reported 578 feet depth. The situation at this time was as follows: the main batteries were considerably depleted from sustained high speeds submerged; depth control still had not been restored and was getting more difficult rather than easier; the water level in the after engine room was rising and had reached the main motor casings; and pump suction could not be obtained aft to correct trim due to the clogged bilge strainers. As the depth was apparently already 578 feet and slowly increasing, the Commanding Officer decided that the only chance of survival for the ship lay in surfacing at once and attempting to fight off the enemy escorts. Therefore, at 2030, seventeen minutes after first being attacked, SALMON started to blow tanks for a battle surface.

7-14. SALMON twice reached depths greater than the maximum indication of her 450 foot depth gauge and on each of these occasions depth readings were thereafter obtained from a control room sea pressure gauge calibrated in pounds per square inch. This method of determining depth was of course only as reliable as the gauge itself. No information is available as to whether this particular gauge was later checked for accuracy of calibration. However, it is known that numerous other pressure gauges, meters and instruments were deranged by shock. It should be noted that since the maximum depth apparently reached, 578 feet, was measured at the control room, the approximate 20 degree up angle on the boat at that time still further increased the submergence at the after end of the pressure hull, resulting in a depth of slightly more than 600 feet at the after bulkhead of the after torpedo room. This

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depth is greater than that at which collapse of the pressure hull would be expected to occur. Although astounding, it cannot be said to be impossible because there is considerable variation in the strength of submarines by reason of variations in the yield strength of the steel used in construction, which varies from heat to heat, and in the thickness of the steel which, by specification tolerances, is not and cannot be required to be exactly the nominal thickness.

7-15. The fact that the stern planes were jammed in full dive position during SALMON'S inadvertent submerged gyrations was a help rather than a hindrance. This was because the boat became heavy overall and heavy aft and the stern planes offered a moderate amount of support tending to hold the stern up. The action of the stern planes on full dive was also beneficial in that it initially permitted some control over the attitude of the boat by use of the bow planes so as to maintain a reasonable up angle in order that the hull itself could be utilized as a plane to counteract the effect of being heavy overall. Later, as additional water entered the engine rooms and caused the boat to become progressively heavier aft, the smallest up angle which could be kept on the boat at emergency speed ahead was approximately 20 degrees even though the bow planes were placed in full dive position. It should be noted that had the stern planes been jammed in hard rise position, the effect of the planes together with the boat being heavy aft would have resulted in such a large up angle that SALMON would have been forced to surface almost immediately.

7-16. Although structural deformation was extensive, particularly in way of the forward and after engine rooms, in no place were the pressure hull or pressure tanks ruptured or torn and watertight integrity remained intact except for the profuse leakage which occurred at various pressure fittings. From the nature of the deformation of the pressure hull over the engine rooms and the fact that SALMON far exceeded its test depth, particularly aft by reason of the up angle while at great depth, it is believed that there is considerable probability that the pressure hull damage was caused by excessive submergence depth rather than by the depth charge attack.

7-17. The pressure hull plating between tank tops was generally depressed between frames 95 and 170. The indentation lobes in this area were for the most part confined to the pressure hull plating between frames only and were discontinuous with lobes in the adjacent frame spaces. Pressure hull frames within the same area were in some cases slightly tilted or buckled (Photo 7-1). No frames tore free from the hull plating. The area of heaviest deformation was between frames 130 and 145, with a maximum pressure hull indentation of about two inches between frames 137 and 139 (Photos 7-2, 7-3 and 7-4). Some distortion also extended a short distance below the tank tops. Forward of frame 95 and aft of frame 170 no structural damage was apparent. The pressure hull plating of the after trim tank was considerably depressed between frames undoubtedly as a direct result of the excessive hydrostatic pressure to which the hull was subjected when SALMON reached a depth of about 620 feet in that area (Photo 7-5).

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7-18. The topside main engine air induction piping leading to the engine rooms completely collapsed and flooded (Photos 7-6 and 7-7). This collapse action probably occurred in two distinct stages: (a) initial partial flattening of local areas of the induction piping by depth charge pressure alone and (b) subsequent complete and longitudinally progressive collapse by direct hydrostatic pressure acting against the weakened unsymmetrical areas caused by (a). Flooding of the induction system alone caused SALMON to be heavy overall by about 13,500 pounds.

7-19. In addition to the collapse of the main induction piping, much other damage was sustained by materiel located outside or attached to the pressure hull. Wood decking and steel framing of the superstructure deck in the area of pressure hull damage were distorted and broken up, requiring extensive renewals. The master vent valve for MBT No. 1 jammed in the open position and remained so until forced shut by hand from topside after surfacing. The master vent valves for MBT Nos. 2E, 2F, 2G and 2H also jammed open but were closed by use of much leverage on the hand wheels. Due to distortion of structure and displacement of vent riser piping, the master vent valves for safety tank and MBT Nos. 2A, 2C, 2E and 2G could not be completely closed, lacking seating by from one to two inches. The vent risers for FBT No. 7 and MBT Nos. 2C, 2E and 2G were ruptured. Over 7,000 gallons of fuel oil were lost from FBT No. 7 through the damaged riser and the displacement of this oil by heavier sea water caused an increase in weight aft of about 11,000 pounds. All starboard tank emergency vent valves leaked and operated with difficulty. The low pressure blow lines to FBT Nos. 7 and 9 were ruptured, the line to FBT No. 7 apparently having been pierced by a solid object (Photo 7-8).

7-20. The outboard mushroom valve for the main induction and ship's ventilation exhaust trunk in the conning tower fairwater at frame 85 was warped slightly, preventing complete seating. No. 1 main engine muffler was dished in considerably and the surrounding decking broken up. All main engine outboard double-seal conical type exhaust valves leaked. Safety tank flood valve jammed in the open position and could not be closed. The residual drain piping in MBT No. 2E ruptured inside the tank. The radio antenna trunk system and the four-inch ammunition ready service stowage case, both located in the conning tower fairwater, flooded completely. On the bridge, the target bearing transmitter pressure-proof binoculars cracked, partially flooding, and the transmitting selsyns were deranged. The bridge pressure-proof 7MC speaker forward also flooded. All radio and the APR antennae insulators fractured. The one and one-half inch thick glass in the bridge pressure-proof gyro repeater granulated. The four-inch deck gun sights cracked and flooded, although the gun itself fortunately remained completely operable. Both periscope

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head staunching plates fractured and the tubes flooded. No other damage occurred topside.

7-21. Flooding occurred in the deck access trunks to the after battery room at frame 90, the forward engine room at frame 125 and the after torpedo room at frame 170. All three of these trunks fortunately had been provided with the secondary boiler-type hatches at the lower ends of the trunks as authorized by BuShips ltr. C-SS/S16-3(515-815) of 28 February 1944. The outer hatches for the after battery and forward engine room access trunks were structurally undamaged and remained seated. Leakage was due to gasket damage plus excessive hydrostatic pressure. These two trunks flooded completely but the secondary hatches held and prevented water from entering the pressure hull. The after torpedo room access trunk upper hatch was forced open by the depth charge explosions to about a 30 degree angle and consequently left the trunk wide open to the sea. Here again the secondary hatch at the lower end of the trunk held tight under full sea pressure and without question saved the boat. To eliminate such a hatch casualty as the above, the installation of emergency securing turn-buckles to prevent the upper hatches from opening momentarily more than about two inches during depth charging was authorized by BuShips dispatch of March 1944. The turnbuckles had been installed on all of SALMON'S access hatches but had not been rigged on those which were backed up by secondary hatches.

7-22. In the conning tower, damage due to depth charging caused severe leakage at depths below 200 feet through the stuffing boxes of both periscopes, the steering wheel shaft packing, and around the gasket of the upper hatch. Some leakage is also reported to have occurred through electrical cable stuffing glands at deep depths. The conning tower bilges overflowed, both periscope wells flooded and considerable water drained through the lower hatch to the control and pump rooms. The IMC announcing system was put out of commission and the station relays were inoperative. The motor controller switch for No. 1 periscope was dismounted and the light switch for the TDC was broken.

7-23. In the control room the damage was relatively minor. The TP-TR panel was dismounted and many indicator bulbs were broken. The main gyrocompass panel short-circuited. The starboard engine order telegraph and telephone ringing circuit junction boxes fractured and short-circuited. About one-half of the pressure gauges were jarred out of calibration. Gauges that were properly shock mounted were reported to have apparently been unharmed. The tank type magnetic compass lost all directivity. Many light bulbs were broken. The fathometer went out of commission due to shock. The 200-pound air valve to the whistle topside and depth gauge sea chest blow valves

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jarred open. The 220-pound service air distribution manifold leaked at the piping connections.

7-24. In the pump room, damage was quite serious. Auxiliary power forward was lost temporarily when the breaker aft in the maneuvering spaces tripped open. The breaker was quickly reset, however. Water draining from the conning tower and the hull ventilation drain flooded the bilges to a waist-high depth at the after end (20 degrees up angle). The following pump room electrical equipment was flooded out: Nos. 1 and 2 high pressure air compressor motors, SD radar mast hoist motor, two circulating water pump motors for air conditioning, and the periscope lower limit switches. The overload relays on Nos. 1 and 2 low pressure blowers tripped and Nos. 2 and 3 I.C. motor generator regulators short-circuited. The stems of sea valves in the circulating water lines to the air conditioning and high pressure air compressors were bent between the bonnets and the valve discs. Various hydraulic system piping and fitting leaks throughout the boat made it necessary to secure the main hydraulic plant until the sources of leakage could be isolated or repaired. The hydraulic plant itself was undamaged. Apparently no misalignment of any auxiliary equipment due to shock occurred in the pump room. The trim and drain pumps continued to run although in some compartments bilge suction strainers became clogged with loose cork.

7-25. In the forward torpedo room, the bow plane rigging motor panel was deranged and upon surfacing the planes had to be rigged in by hand. The QC sound gear shaft was forced up despite the holding pins, and its hydraulic supply line was torn loose. The pitometer log was found to operate erratically. The diving alarm short circuited. The officers' watercloset discharge line ruptured inboard of the hull valve.

7-26. No damage occurred in the forward battery compartment with the possible exception of one battery cell. This cell may have been cracked, for reference (a) reports that it had a high ground reading and that the electrolyte level was not visible. No subsequent information on the cell is available.

7-27. In the after battery compartment damage was comparatively minor. In the crew's mess room both the ship's supply ventilation hull flapper valve and the No. 2 sanitary tank overboard vent valve leaked heavily. Sea water flooded out the electric ranges in the galley. The battery cells and strongbacks in this compartment were unaffected and the well was dry. Several light bulbs and one mirror were broken and an oxygen bottle was torn loose from its overhead stowage position.

7-28. In the forward engine room, the No. 1 main engine completely flooded through the exhaust piping system. The depth charging caused

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the outboard exhaust valve to leak and jarred the inboard exhaust valve (gate) partially open. The No. 4 liner of this engine also fractured. The No. 1 engine air starting line ruptured, causing serious air leakage. No. 2 main engine also partially flooded through the exhaust system but was otherwise undamaged. The main engine circulating water sea suction and discharge valve bonnets leaked profusely around stems and flange gaskets at deep depths. As previously mentioned, serious leakage occurred at the fuel ballast tank riser inboard vent lines, the vent valves having torn loose from the hull. Water flooded the bilges and at 20 degrees up angle reached a height of 18 inches on the No. 2 generator. This generator was flooded with a mixture of oil and water but ran well after it was pumped out and wiped down. The forward engine air induction hull flapper valve and the inboard exhaust valve (gate) for No. 2 main engine jammed closed, the latter due to hull distortion forcing the valve stem brace out of line (Photos 7-11 and 7-12). Coil leaks developed in both of the Kleinschmidt electric vapor compressor stills and only salted distillate could be produced. The IMC speaker, diving alarm, fresh water expansion tank, 200-pound service air compressor motor and the fuel and lubricating oil purifiers were dismounted by shock. Several water and hydraulic pipe lines were ruptured or jarred loose at connections. Various non-shockmounted pressure and temperature gauges were broken or put out of calibration. Bilge suctions clogged with cork and debris.

7-29. In the after engine room, although hull deformation was severe, damage to interior equipment was relatively minor. As stated in paragraph 7-9, the hull plating was dished in sufficiently to cause the stern plane hand tilting shaft to bind with the stern planes in "hard dive" position. No. 1 lighting motor generator voltage regulator control was deranged, putting the ship temporarily in darkness. The emergency lighting leads in both engine rooms parted and fixtures were wrecked. Main engines Nos. 3 and 4 (propeller engines) were undamaged although they partially flooded through the exhaust system. Several main engine lube oil lines parted or ruptured. All four main motor plants were undamaged with the exception of the bearing oil supply line nipples to No. 3 main motor which cracked in the housing and a ruptured circulating water supply line to the No. 3 main motor air cooler. The main control cubicle frame and covers were distorted when the hull dished in overhead (Photo 7-10) and one main motor contactor flash chute was dismounted. However, the entire submerged propulsion plant remained fully operable during and after the depth charging and was a major factor in the survival of the ship since depth control, erratic as it was, was aided by use of fast speeds ahead while submerged. That propulsion power was not lost was due in large measure to the main motor and battery contactor positive locks installed per ShipAlt SS137 which prevented tripping by overload and shock. Sea water leaked profusely through the fuel ballast tank riser inboard vent lines, as in the forward engine room. The bilges flooded and could not be pumped since cork insulation had clogged drain line suctions. The water level reached the lower casings of the main motors and this was a principal factor in the decision to surface.

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7-30. In the after torpedo room, the "tee" connection in the No. 3 ballast tank vent riser was forced in by the distortion to the pressure hull overhead but remained tight. The stern plane tilting drive shaft coupling was shattered and the drive worm gear housing was dismounted. The capstan motor controller panel contactors jarred open and had to be reset by hand. The oil supply line to the steering hydraulic manifold was torn loose, making it necessary to shift to hand power and later to emergency power from the main hydraulic plant. No. 6 torpedo tube shutter moved to the open position. The residual drain piping hull flange for MBT No. 3 was partially sprung with minor leakage resulting.

7-31. When SALMON battle-surfaced at 2030, after seventeen hectic minutes of attempting to remain submerged under conditions which rendered depth control impossible, her situation was still very dangerous. Decks were awash and the boat had a fifteen degree list to starboard. Most of the available high pressure air had been expended due to numerous internal leaks and the large amount of air required to start the boat up from the extreme depth of 578 feet while simultaneously losing much of it through damaged ballast tank risers and leaking vent valves. The remaining high pressure air was limited to 1200 pounds in one bank only and no replenishment could be made since both high pressure air compressor motors had flooded. Lack of air plus the depleted condition of the storage battery made any further diving for evasive purposes impossible. The low pressure blowers could not be started immediately since the low pressure volume tank had flooded with sea water and the blower motor panel contactors had tripped open and had to be reset. Consequently no air was available with which to blow tanks in order to correct list and increase freeboard. This in turn rendered gun operations difficult. The feelings of SALMON'S officers and men after the decision was made to surface can be well imagined when it is remembered that there was no information at that time as to the whereabouts of the Japanese anti-submarine vessels and that there was no way of knowing whether the surface Diesel engine propulsion plant and the deck guns were in working order, both of which would probably be required in order to make good their escape.

7-32. SALMON found herself up moon from all four escorts, the nearest being about 7,000 yards distant. None of the escorts at this time apparently detected SALMON for they gave no immediate indications of having discovered her presence and were still dropping occasional depth charges near the scene of the original attack, a large oil slick having been left by the loss of oil from FBT No. 7. This delay was invaluable for it enabled SALMON to take damage control measures, man guns, correct list, increase freeboard, obtain partial operation of the surface propulsion plant and repair vital auxiliary machinery before the first escort closed in for an attack.

7-33. At 2032, two minutes after surfacing, the No. 3 main engine and the battery were put on composite drive propulsion. Under this arrangement on SALMON, power could be transmitted to the propeller

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shafts by direct drive from Nos. 3 or 4 engines through reduction gears and also concurrently by electric motor drive through the same reduction gears by taking current from either the battery or the Nos. 1 and 2 main engine driven generators. By 2050, both Nos. 3 and 4 main engines were on propulsion. Inboard exhaust valves (gates) which had jammed in the closed position were opened by aid of chain falls. By 2100 the low pressure volume tank was dewatered, motor panel contactors reset and the blowers were started. All ballast tanks were immediately blown, removing the list and increasing freeboard. The master vent valves were found to leak badly and therefore the emergency vent valves were slowly closed while air was still being forced into the tanks. The flood gates were then closed.

7-34. Up until 2100, none of the enemy escorts had made any effort to close. At that time, however, the closest escort apparently detected SALMON for the first time. He illuminated SALMON by searchlight from about 5,000 yards and fired a few wild salvoes in her general direction with a deck gun believed to have been three-inch or larger, and several rapid fire guns, believed to have been about 37mm, mounted amidships and forward. The escort at this time, however, made no determined effort to shorten the range.

7-35. By 2115, forty-five minutes after surfacing, the No. 2 main engine was started and put on propulsion, reducing the load on the battery to auxiliary purposes only. This made a total of three engines on the line. When an attempt was made to start the completely flooded No. 1 main engine, the drive shaft of the scavenger blower for the engine fractured. Shipboard repairs could not be made and this engine remained out of commission until the ship returned to the west coast of the United States. The best possible speed with three engines was 16 knots. These three propulsion units performed satisfactorily and no reduction gear noise or misalignment of the propeller shafting was noticeable. Power steering was now in commission and the stern diving planes had been worked back to zero angle. The auxiliary gyrocompass was again in operation. Bilges had been pumped dry. Since the radio, VHF and APR antennae had been knocked off, an emergency wing antenna was rigged for transmitting. The SJ radar transmitter had been flooded out by a water spout which rose from the conning tower bilges when the upper conning tower hatch was opened upon surfacing. This was caused by the sudden release of accumulated internal pressure in the boat from numerous air system leaks.

7-36. At 2130, SALMON sent radio notification to SILVERSIDES and TRIGGER of her condition and position. Six U.S. submarines were in the vicinity and several of these opened up with numerous voice radio messages in an attempt to impress the Japanese with the strength of the opposition forces. From 2115 to about 2400, the first escort, having superior speed, forced SALMON to run in a large circle and fired repeatedly but secured no hits. SALMON conserved ammunition and fired her four-inch deck gun only when hits were fairly well assured. Since the sights had been shattered, the gun was aimed by the first loader coaching the pointer and trainer. At about 2400, with the other three

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escorts in a line to southward and from 4000 to 8000 yards distant, the first escort became apparently impatient with lack of results so far and made his first determined effort to close the range. He passed SALMON'S port beam at a range of about 2000 yards but the resulting interchange of fire was ineffectual on both sides. As the escort passed abeam, SALMON headed for a rain squall which had formed to south-westward. The enemy then headed to intercept and SALMON immediately staged a surprise offensive attack. Turning directly toward the patrol craft, SALMON charged in with all available speed and passed at about fifty yards distance on opposite course, raking the escort from end to end with 20mm, 40mm and 50 cal. machine guns and probably killing most of the enemy personnel topside. Damage from enemy light fire was minor. This maneuver knocked all the fight out of the Japanese escort and SALMON once again headed toward the rain squall. The nearest of the other three escorts then opened fire and commenced closing but turned away after several small caliber hits and a four-inch near miss had been secured by SALMON at a range of about 2000 yards. At 0045, 31 October, SALMON entered the rain squall and shortly afterwards lost all contact with the enemy escorts.

7-37. SALMON proceeded toward Saipan on three engines, making a speed of about sixteen knots. Her condition at this time was still very dangerous for she was limited to surface operations only, her best speed was less than that of most Japanese anti-submarine escorts, and she was still within easy aircraft bombing distance from the Japanese home islands. At 0532, SALMON radioed for assistance from U.S. submarines in the near vicinity and at about midnight on 31 October was joined by TRIGGER, SILVERSIDES and STERLET, about 450 miles southeast of Kyushu. SALMON had been forced to stop in this position in order to repair a serious main engine lube oil leak which developed on a line located in a difficult position to reach. While awaiting rendezvous, several torpedoes were fired at her by a Japanese submarine but all missed and SALMON immediately got underway again. The friendly submarine screen was maintained all the way to Saipan and in addition, starting at dawn on 2 November, continuous daylight air coverage was provided. At 1950 on 3 November, SALMON moored alongside FULTON (ASH) in Tanapag Harbor, Saipan.

7-38. SALMON received temporary repairs at Saipan and proceeded via Pearl Harbor to the Naval Drydocks, Hunter's Point, arriving on 2 December 1944. There she was surveyed by the Board of Inspection and Survey and a decision was made to send her to the Navy Yard, Portsmouth, N.H., for minimum damage repairs necessary to use her as a training and experimental submarine. Sufficient repairs were made at Hunter's Point to render the ship seaworthy for her surface run to Portsmouth. Some machinery was overhauled and the hull above the waterline was painted. The hull and superstructure were left intact except for scrapping of the main engine air induction piping and renewal of damaged wooden decking. SALMON departed from Naval Drydocks, Hunter's Point, on 27 January 1945, and arrived at Navy Yard, Portsmouth, on 17 February 1945.

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7-39. After another survey, the Chief of Naval Operations on 5 October 1945 recommended halt of further repair work and disposition by scrapping. SALMON was decommissioned on 4 April 1946 at the Naval Shipyard, Portsmouth, New Hampshire, and subsequently scrapped.

7-40. Prior to her decommissioning, SALMON was officially credited by ComSubPac with sinking seven ships (1 CL, 3 AK, 2 AO, 1 DD), a total of 31,800 tons, and damaging eleven ships (1 CL, 6 AK, 2 AO, 2 PF), a total of 56,400 tons.

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Photo 7-1: SALMON (SS182). View looking to starboard at pressure hull between tank tops, showing a typical T-section frame distortion. This failure illustrates the need for frames having greater transverse and torsional rigidity.

Photo 7-2: SALMON (SS182). General view, looking aft, showing deformation in pressure hull plating between tank tops over the after engine room, frames 129-137.

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Photo 7-3: SALMON (SS182). Pressure hull deformation between frames 137-143, over the after engine room.

Photo 7-4: SALMON (SS182). Depression in pressure hull plating between frames 137-139. Depth of depression is estimated to be about 2 inches.

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Photo 7-5: SALMON (SS182). View showing depressions in shell plating between frames in after trim tank, believed due to over-depth failure.

Photo 7-6: SALMON (SS182). View showing portion of collapsed engine air induction piping in superstructure.

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Photo 7-7: SALMON (SS182). Collapsed engine air induction piping after removal from ship.

Photo 7-8: SALMON (SS182). View showing hole in low pressure blow line (10-pound) to FBT No. 7.

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Photo 7-9: SALMON (SS182). View in after engine room showing typical damage to cork insulation. Debris in engine room bilges clogged the drain line suctions.

Photo 7-10: SALMON (SS182). Pressure hull deformation in overhead of after engine room in way of propulsion control cubicle. Note damage to interior communication connection box terminal strips.

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Photos 7-11 and 7-12: SALMON (SS182). Side and front views showing displacement of brace for stem of No. 2 main engine inboard exhaust valve due to pressure hull distortion in forward engine room. Binding of this brace against the valve stem prevented valve from being opened by hand. Later opened with aid of chain fall.

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Photo 7-13: SALMON (SS182). Photo taken on 10 August 1944 at Navy Yard, Mare Island.

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Plate VII: Depth Charge Damage


SECTION VIII

U.S.S. GRENADIER (SS210)

Loss in Action

Off Malaya

22 April 1943

Class

SS198

Builder

Navy Yard, Portsmouth, N. H.

Commissioned

1 May 1941

Length (Overall)

307 ft. 2 in.

Beam (Extreme)

27 ft. 3 in.

Submergence Depth (Designed Maximum) (Axis)

250 ft.

Displacements

Standard

1475 tons

Emergency Diving Trim

1980 tons

Submerged

2359 tons

Draft (Mean, Emergency Diving Trim)

16 ft. 8 in.

Type of Propulsion

Diesel Electric Reduction Drive

Main Engines (4)

Fairbanks-Morse 38-D-8-1/8

Main Motors (4) and Generators (4)

Elliott Co.

References:

(a) Enclosure (C) to ComSubPacAdmin ltr. FF12-10(A)/A4-1 (1)/A16-2, Serial 00349 of 21 September 1945 (Commanding Officer GRENADIER Statement Concerning Loss of Vessel).
(b) Account of Loss of GRENADIER as Related to Cdr. I.F. Duff, (MC), USNR, by Lt. Cdr. A. Toulon, Jr., USN (Engineer Officer) on 7 February 1946.
(c) ComSubPac Report Entitled "Enemy Anti-Submarine Measures", no date or file number given (Account of Loss of GRENADIER).

Photograph No. 8-1

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8-1. On 21 April 1943, while operating off the Malay Peninsula during her sixth war patrol, GRENADIER sustained heavy damage to the after portion of the ship as the result of a Japanese aircraft depth bomb attack. The most serious casualty which occurred, and which directly caused GRENADIER'S loss, was the complete immobilization of her propulsion plant due to derangement of the main control cubicle and severe misalignment of the propeller shafting. All efforts by ship's force to effect emergency repairs were unsuccessful. Early the next morning, GRENADIER was abandoned and scuttled by her own crew to prevent imminent capture by an approaching Japanese merchant ship. This report is based on the information contained in the references. The references are accounts furnished from memory by various survivors upon their release from Japanese prisoner of war camps at the end of the war, nearly two and one half years after the action occurred. Therefore, the source data are not as complete and cannot be considered to have the same degree of accuracy as formal war damage reports written shortly after actions occurred.

8-2. The sixth war patrol of GRENADIER was conducted in the waters of the Indian Ocean off the west coast of the Malay Peninsula. Late in the evening of 20 April 1943, while making a surface search of an area about ten miles to the west of Lem Voalan Strait, GRENADIER sighted two Japanese merchant vessels. The moon being full and visibility conditions excellent, GRENADIER proceeded to circle astern of the ships with the intention of determining their course and speed. While still eight or nine miles away, however, she was detected and the enemy ships thereupon made a radical course change.

8-3. GRENADIER then proceeded to a position ahead of the target ships and submerged to await their arrival, but at early dawn of 21 April the Japanese again changed course before the range had been closed sufficiently to permit torpedo fire. When only the smoke of the ships was visible on the horizon, GRENADIER surfaced and commenced a run to a point which it was estimated would place her in a favorable position for attack if the enemy ships next changed course in conformance with known Japanese convoy doctrine.

8-4. At 0836, when still about 15 minutes running time from the intercept position previously selected to await the enemy, a Japanese single-engined plane was sighted approaching from the port quarter. GRENADIER thereupon made a quick dive.

8-5. When GRENADIER reached 90 foot depth, 15 degrees right rudder was ordered. At 0837, as the ship was passing 120 feet depth, a tremendous detonation occurred close over the maneuvering room and heeled the boat 10 or 15 degrees to port.1 Lighting, auxiliary power and main propulsion were immediately lost. Emergency lighting was switched on and functioned satisfactorily. GRENADIER continued on down while attempts were made aft to regain power. When a depth of about 200 feet was reached, word was received that a fire had started in the maneuvering room so the boat was set on the bottom in about 260 feet of water.

8-6. The bomb detonation was reported to have been centered about degrees to starboard from the vertical above and abreast the after


1 Japanese records obtained at the end of the war contain no mention of this attack.

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bulkhead of the maneuvering room. The severity and extent of the damage indicate that the weapon was probably a 250 Kg. Mk. 2 antisubmarine depth bomb containing 317 pounds of Type 98 explosive. This is the largest depth bomb known to have been developed by the Japanese and was commonly used for anti-submarine work. The depth setting employed in this instance was probably that corresponding to the standard "25 meter" fuzing frequently used by the Japanese. This should have caused detonation in the vicinity of 70 to 80 foot depth or about 40 feet above and to starboard of GRENADIER's pressure hull abreast the after end of the maneuvering room. The Commanding Officer stated that the noise and jarring effect of the detonation on the ship were as though "two express trains collided". Beyond a few superficial lacerations and bruises there were no personnel casualties.

8-7. The fire in the maneuvering room was reported to have started as a result of the cutting and short-circuiting of the main motor power cables above the control stand when the pressure hull overhead dished in sufficiently to come in contact with the power cage of the main control cubicle, and also by arcing of contactors in the control stand itself. The burning material consisted of the hull insulation cork sheathing, electric cable sheathing, stores, cleaning rags and paint. Dense noxious smoke was generated in large quantities. When it became apparent that no immediate headway was being made in attempts to extinguish the fire, and with smoke spreading throughout the boat, the Commanding Officer ordered the maneuvering room sealed. About one-half hour later, the compartment was re-entered by a firefighting party using escape "lungs" as respirators to filter out the smoke and the fire was smothered with CO2 from portable fire extinguishers. At some time during this period two men were overcome by smoke. The escape "lungs" were used since rescue breathing apparatus was not available. It was reported that the "lungs" were clumsy and that difficulty was experienced in keeping the mouth-pieces in place.

8-8. The pressure hull plating and frames were severely dished inward from the after bulkhead of the engine room to the after bulkhead of the after torpedo room. Maximum dishing was sustained in way of the bulkhead separating the torpedo room and the maneuvering room, four to six-inch indentations occurring at the starboard forward end of the after torpedo room. The bulkhead itself was distorted and forced to port, apparently bending the port and starboard propeller shafts at both stern tubes, and the watertight door seat was sprung so that the door could not be completely closed. The maneuvering room control cubicle cage was twisted out of shape and deck plates and support frames were bent.

8-9. Although in no place was the pressure hull proper reported to have been torn or ruptured, there were at least three sources of major leakage into the interior of the boat. The first was through the maneuvering room air induction hull valve, its seat being so badly distorted that a two-inch stream of water poured through from the flooded topside engine induction piping onto the electrical equipment of the main propulsion control cubicle beneath. The second source of leakage was through the distorted riveted joints of the maneuvering room hard

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patch and this also resulted in sea water spraying onto the control cubicle. It was reported that this hard patch was partially separated from the hull. The third source of major leakage was through the after torpedo loading hatch. The bossing structure supporting the hatch seat was distorted to such an extent that the torpedo loading hatch transverse compression strut was bent about 10 to 15 degrees from its normal centerline and the hatch opening became elliptical in shape rather than circular. The hatch cover lacked seating to the extent that the Commanding Officer reported he could insert his hand between the seat and the hatch cover. Almost half of the circumference of the hatch gasket was badly cut.

8-10. Upon extinguishing the fire in the maneuvering room, a bucket brigade was formed between the maneuvering room and the forward torpedo room in an attempt to keep the water level below the level of the main motors. Many men lost consciousness from heat prostration and physical exertion. Eventually, a jury rig was established so that electrical power for the drain pump could be taken from the forward battery and incoming water was thereafter kept to a satisfactory level by pumping alone. Every effort was made to protect the control cubicle and other electrical equipment in the maneuvering room from the shower of sea water through the hard patch and induction valve, but shields could not be effectively rigged due to overhead interference between the control cubicle and the hull. As a result, all vital electrical equipment in the control cubicle became saturated with salt water.

8-11. In the after torpedo room, all torpedo tubes were put out of commission, presumably due to misalignment of the entire tube nest and damage to stop bolts, torpedo guide studs, gyro setting spindles and blow and vent piping systems and fittings. Steering system hydraulic lines were ruptured. Many gauges were dismounted and deranged. Bunks and torpedoes were dislodged and thrown about.

8-12. Damage forward of the maneuvering room was apparently relatively minor. In the engine room, hydraulic lines to the main vent valves carried away. No other damage was reported in this compartment although there must have been at least considerable minor derangement of equipment, piping systems, gauges and instruments. In the crew's messroom, dishes and phonograph records were thrown about and broken. In the radio room, the radio receivers were dislodged from their mountings and the transmitter was knocked over. The radio gear was subsequently put back in commission. The insulators in the radio antenna trunk were also found to have broken.

8-13. The ship's force worked all day attempting repairs and restoring order where possible. No more enemy attacks were received. Efforts to restore propulsion power were considerably hampered by the continued intake of water over the control cubicle and by several minor electrical fires which started at various times.

8-14. During this period, breathing conditions became very trying for the eight officers and sixty-eight men aboard. The air conditioning

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and ventilating systems were not working. The maneuvering room fire had created large quantities of irritative smoke and in addition had consumed some of the available oxygen from the atmosphere. About eight cans of carbon dioxide absorbent were spread out in the after battery compartment and oxygen was bled into the boat. Men not working were encouraged to lie down. Despite these measures the ship became very hot and humid and headaches were common.

8-15. At 2130, after 25 hours submerged, GRENADIER surfaced under cover of darkness in order to ventilate the boat and aid repairs by stopping the maneuvering room leakage. The ship was cleared of smoke at this time by running the main Diesel engines. After several hours' work a jury rig was established which enabled power to be supplied to the motors of one shaft. However, the shaft could be turned over only at very low speed, apparently due to severe stern tube or strut bearing misalignment or bending of the shaft itself. It was impossible to move the control stand levers into the second stage resistance. Approximately 2750 amperes were required to turn the shaft although the current normally required was only 450 amperes.

8-16. By about 0400 to 0500 the next morning, 22 April, all efforts to restore propulsion had proved of no avail and it became apparent that nothing further could be accomplished in view of the magnitude of the damage and the limited repair facilities available to the ship's force.

8-17. Plans were then made to rig a sail with the intent of moving the ship closer to the shore where the crew could be disembarked and the ship blown up. This scheme, however, was soon shown to be futile and was abandoned.

8-18. At about 0600 a ship was sighted proceeding from the northwest out of Lem Voalan Strait and shortly afterwards smoke from what appeared to be a patrol craft was sighted to the southeast. At this time GRENADIER could neither run nor fight. It was considered inadvisable to resubmerge since a stationary dive would have been required without power, there were several leaks of serious nature through the hull and the true trim of the boat was not known due to having transferred large quantities of water and the loss of fuel oil through ruptures in external tanks. Offensive action against the enemy was not possible since the three-inch deck gun had been damaged and torpedoes apparently could not be fired. The decision was therefore made to scuttle the ship. Classified papers were destroyed and radar, radio, sonar and TDC equipment was demolished.

8-19. While preparations were in progress for abandoning ship, a single-engined Japanese plane, similar to the one of the preceding day, commenced a run on GRENADIER from the port side but was forced away by the return fire from the two 20mm and two .30 caliber machine guns. The plane then made a second run on GRENADIER'S port side and was again fired upon. When directly overhead, the plane dropped an aerial torpedo which struck and detonated in the water about 200 yards from the ship. Subsequent information indicated that the pilot of the plane died that night as a result of wounds received from GRENADIER'S fire and a crash when landing at Penang.

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8-20. The crew was then lined up at quarters forward of the conning tower, leaving one man below to open the tank vents. There being an insufficient number of life jackets available for all hands, mattress covers were inflated with air prior to abandoning ship. In addition, one rubber life raft was available for the sick and those who could not swim. When the ship from the northwest, an 1800-ton converted merchant vessel, arrived within two miles distance, all hands were ordered over the side and the man below opened the vents. GRENADIER sank quickly, stern first.

8-21. The entire complement, seventy-six men and officers, were taken aboard the Japanese merchant ship and subsequently landed at Penang, Malay States. Of these, seventy-two men survived to the end of the war. Prior to her loss, GRENADIER was officially credited by ComSubPac with sinking six ships (3 AK, 2 AP and 1 AO), a total of 40,700 tons, and damaging two ships (both AK), a total of 12,000 tons.

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Photo 8-1: GRENADIER (SS210). Photo taken on 27 December 1941.

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SECTION IX

U.S.S. SCAMP (SS277)

Depth Bomb Damage Aft

Off Mindanao, P.I.

7 April 1944

Class

SS212

Builder

U.S. Navy Yard, Portsmouth, N. H.

Commissioned

18 September 1942

Length (Overall)

311 ft. 8 in.

Beam (Extreme)

27 ft. 3 in.

Submergence Depth (Designed Maximum) (Axis)

300 ft.

Displacements

Standard

1525 tons

Emergency Diving Trim

2050 tons

Submerged

2415 tons

Draft (Mean, Emergency Diving Trim)

6 ft. 10 in.

Type of Propulsion

Diesel Electric Reduction Drive

Main Engines (4)

Fairbanks-Morse 38-D-3-1/8

Main Motors (4) and Generators (4)

General Electric Co.

References:

(a) C.O. SCAMP conf. ltr. SS277/A16-3/A9, Serial 016 of 22 April 1944 (Report of War Patrol Number Seven).
(b) C.O. SCAMP ltr. SS277/P13-5, Serial 002 of 24 April 1944 (Report of War Damage).
(c) ComSubRon Eighteen ltr. FC5-18/L11-1/(SS277), Serial 0012 of 25 April 1944 (First Endorsement to CO. SCAMP War Damage Report).
(d) CinC U. S. Naval Drydocks, Hunter's Point conf. Report SS277-S8800-131693 of 9 April 1945 (Supplementary Report of SCAMP War Damage).
(e) BuShips Code 660u conf. Memorandum of 30 May 1944 (Report of Inspection of SCAMP War Damage at U.S. Naval Drydocks, Hunter's Point by Mr. W. H. Fifer, Bureau of Ships).

Photographs Nos. 9-1 through 9-15 (furnished by CO. SCAMP, CO. TANGIER (AV8) and Naval Drydocks, Hunter's Point)

PLATES IX-1 and IX-2

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9-1. During her seventh war patrol SCAMP was attacked by a Japanese float plane shortly after submerging and sustained severe damage from a near-miss depth bomb detonation. The deformation which occurred to both the inner and outer hull structures as a result of this attack is the most severe known to have been survived by any U.S. submarine during World War II. It is considered remarkable that SCAMP was able to continue submerged operations after receiving the damage even though all propulsion power was lost for a fifteen-minute period during which the boat became heavy overall due to flooding of the main induction system, leakage of water into the hull and loss of fuel oil from a fuel ballast tank. This report is based on the information contained in the references. The Photographs were furnished by C.O. SCAMP, C.O. TANGIER (AV8) and U.S. Naval Drydocks, Hunter's Point. PLATES IX-1 and IX-2 were prepared by this Bureau and are based principally on the data contained in the enclosures to reference (d).

9-2. SCAMP arrived from her sixth war patrol at Milne Bay, New Guinea, on 6 February 1944. After a two-week refit by FULTON (ASH) followed by an intensive training period, SCAMP departed Milne Bay on 3 March for her seventh war patrol.

9-3. Although wide searches were conducted in her assigned area north of New Guinea, SCAMP made no enemy ship contacts during her first month on patrol. She then refueled at Langemak Bay, New Guinea, on 29 March and departed on 31 March for a new area in the waters between Mindanao and Halmahera Islands. The first enemy ship contact of the patrol was made on 4 April when a Japanese armed trawler was engaged by four-inch gunfire at long range. Two hits were scored on the trawler, causing a slight list and a fire aft, but the action was broken off when the deck gun on SCAMP failed to return to battery after 91 rounds had been fired.

9-4. Three days later, early on the morning of 7 April, SCAMP established contact with a Japanese convoy of three ships, but all efforts to reach a favorable attack position were unsuccessful. Her first attempt, a surface approach before dawn, was frustrated when the enemy made a radical change in base course. A second attempt was made by submerged approach later in the morning but range to the targets could not be sufficiently closed. Further action against this convoy was terminated when, at 0930, a large enemy task force, consisting of two heavy cruisers and four light cruisers screened by four destroyers and five planes, was sighted.

9-5. An approach on the new targets was commenced and an excellent firing position was gained for successive bow and stern tube salvoes. However, just prior to securing the final periscope observation before firing, SCAMP was detected by the enemy destroyer screen and forced to take evasive action. From then until noon she was sporadically depth-charged but no damage resulted. At 1405, after the destroyers had left the area, SCAMP surfaced to radio a contact report regarding the Japanese force but at 1407 an enemy bomber was sighted and she was forced to submerge immediately in order to avoid detection.

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9-6. At 1423 SCAMP again surfaced to attempt to radio the contact report. Although continuous efforts were made, communications had not yet been established when, at 1543, a Japanese float plane, bearing 280° (T) and at an altitude of 1500 feet, was sighted diving on SCAMP from directly out of the sun. The plane was first detected by visual means when at a range of about 440 yards. At this moment SCAMP was proceeding on course 094° (T) at a speed of 15 knots with three engines on propulsion and one engine on charge. She was in a position about forty miles south of Mindanao, P.I., lat. 5° 02 'N., long. 126° 07 'E. The weather was clear, visibility excellent and the sea glassy calm.

9-7. SCAMP made a quick dive in an effort to avoid attack and word was passed to rig ship for depth-charging. The boat submerged with a 7 degree down angle at a speed of about 8 knots, swinging left with full rudder, and was passing forty feet depth when a single terrific explosion occurred off the port side. The resulting damage to SCAMP was extensive and serious. The entire ship vibrated and twisted for several seconds and all hands not holding on to something were thrown off their feet. The noise effect was described in reference (b) as "loud and deep".1

9-8. From available knowledge of types and sizes of bombs commonly carried by Japanese float planes on anti-submarine patrol at this period of the war, it is believed that the weapon used against SCAMP was probably a standard 60 Kg. Mk. 2 depth bomb containing 85 pounds of Type 98 explosive. Based on the damage inflicted and the known effect of underwater explosions on similar type structures, it is estimated that this 60 Kg. bomb probably detonated about frame 77 at a distance of approximately 15 feet from the port side of the pressure hull, centered vertically at the level of the tank tops and abreast FBT No. 5B and the interior transverse bulkhead separating the forward engine room and the after battery compartment. (PLATE IX-1).

9-9. A general survey of the overall damage sustained by SCAMP as a result of the bomb detonation is presented in PLATES IX-1, IX-2 and Photos 9-2 through 9-11. The immediate effects of the detonation which were of serious nature and which caused SCAMP's subsequent inadvertent maneuvers or determined the damage control measures which were employed in an effort to save the ship, are listed below:

(a) Simultaneously with the bomb detonation, a small electrical fire started in the propulsion control cubicle and dense toxic smoke was generated from burning phenolic material. This smoke filled the maneuvering


1 This action was included in the list of anti-submarine attacks assessed as resulting in positive sinkings received from the Japanese at the end of the war. The exact translation of the Japanese comments on this attack is as follows: "Found a floating sub. Direct hit on the rear of the bridge and near-missed the side. A dense oil pool was created measuring 300 x 4000 meters. Air bubbles. The sub sank wriggling to the left". This statement indicates that two bombs were dropped although SCAMP's War Patrol Report and the nature of the damage sustained indicate that only one bomb detonated.

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room and made personnel in that compartment violently ill. All propulsion power was deliberately cut off after the fire started in order to determine the extent of damage to the control cubicle and power circuits and avoid possible further damage. Propulsion was not restored until about 15 minutes later.

(b) The main engine air induction piping topside was torn open at the points of attachment to its welded supports in four places between frames 75 and 78 (Photo 9-5). These ruptures allowed the entire induction system to flood rapidly, causing a loss of buoyancy of about 14,000 pounds. Sea water then entered the interior of the pressure hull through the main induction drains and also around the forward engine room induction hull flapper valve, which would not tightly seat due to distortion of the adjacent hull structure. A total of about 10,000 pounds of water was taken into the bilges through these and other minor leaks.

(c) FBT No. 5B was torn open over a two-foot length between frames 79 and 80 at the knuckle between the margin plate and the tank top outer hull plating (Photo 9-7). This allowed the 7000 gallons of fuel oil in this tank to escape and be replaced with heavier sea water, causing an increase in weight of about 11,000 pounds.

(d) Power operation of the rudder was lost, presumably due to electrical contactors jarring open or fuses blowing in the steering motor control panel. The rudder therefore remained in full left position, which had been set on diving, until a shift was made to hand control about ten minutes later.

9-10. As a result of the sudden loss in buoyancy due to flooding of the main induction system, added weight due to intake of water into the pressure hull and displacement of fuel oil in FBT No. 5B with heavier sea water, both of the latter occurrences being relatively slow, SCAMP became heavy aft and started to settle fast, assuming a large up angle. The subsequent operations which were resorted to in a desperate effort to remain submerged can best be understood by a study of PLATE IX-2. When it is considered that the excess of weight over buoyancy resulted in the ship being about 15 tons heavy overall and heavy aft, and that no power was available with which to propel the ship so that the bow and stern planes and the up angle of the boat could be effectively used for aiding in depth control, the fact that SCAMP neither broached nor went excessively deep during this critical period is considered a great tribute to those who maintained depth control.

9-11. When SCAMP first began increasing depth rapidly, it was decided to blow a sufficient number of tanks to halt this movement. All main vents were still open for the boat had just submerged and the damage had occurred before they were closed. However, when the order was given and executed to close these vents by hydraulic power, nothing happened. It was then noticed that the shock of the detonation had caused the drum-type starter controller for the main hydraulic plant to move to the "off" position, thereby shutting off current to the hydraulic pump motor. The controller was immediately cranked to the "on" position, starting the motor, and all main vents were then

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closed without difficulty.1 when 100 foot depth was reached, the negative tank was blown. At 175 feet, safety tank was blown. The boat still continued to sink, however, so when a depth of 290 feet was reached, air bubbles were put in all main ballast tanks. Although the boat now probably had well over 100 tons positive buoyancy, momentum carried her down to 330 feet where she finally stopped, hung for a brief period and then started to rise, still with a considerable up angle. In the meantime, all hands not required elsewhere had been sent to the forward torpedo room where they squeezed themselves around the torpedo tubes to add weight forward for trim control. Efforts were being made in the maneuvering room to determine the extent of damage to the control cubicle and power circuits before attempting to restore propulsion but personnel were seriously handicapped both by the presence of the dense phenolic smoke and the large up angle on the boat. The rudder was still hard over and consequently the boat continued turning.

9-12. SCAMP, now rising rapidly, was faced with the prospect of inadvertently broaching, and it was decided that if the boat passed 50 feet still going up, a battle surface would be made and the deck guns would be manned against whatever opposition might be encountered. However, by venting and flooding all tanks on the way up, the ascent was checked at 52 feet and the ship started down again. By alternately blowing and flooding tanks, SCAMP was able to remain submerged without power and went up and down three times in this manner. At about 1600, as the boat started down for the fourth time and with pressure in the air banks getting low, the maneuvering room personnel finished checking the main power circuits and the starboard shaft was brought up to turns for two-thirds speed.

9-13. With propulsion power now available, and presumably having gained better trim by maintaining a bubble in the safety tank and pumping or blowing the after trim tank during this period, the ship could now be controlled and shortly afterwards was leveled off at 150 foot depth. About five minutes after the starboard shaft was first turned over, the port shaft was also brought up to turns for two-thirds speed. The rudder was finally placed amidships by shifting to hand hydraulic control but only after the ship had made one complete circle. The sequence of events from the time of the bomb detonation to the restoration of propulsion power, as described in the above paragraphs, consumed about a fifteen-minute interval. Fortunately, no additional enemy attacks were made during this critical period although the trail of oil escaping from FBT 5B and air bubbles from the blowing operations must have disclosed SCAMP's whereabouts very plainly indeed. Presumably, the enemy plane had no more bombs or the pilot felt certain SCAMP had been destroyed.


1 Drum-type starter controllers were particularly susceptible to mechanical troubles and shock damage. ShipAlts SS257 and SS261 of 5 and 10 October 1944, respectively, authorized the replacement of drum controllers for the hydraulic plant and trim pump motors with the much more satisfactory magnetic type push-button controllers.

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9-14. SCAMP commenced evasive action, running at 150 foot depth, and probably still leaving a small trail of oil behind. At this time the ship was considerably out of final trim and very sluggish and hard to control. From 1755 to 1830, ten depth charges or bombs were heard detonating but all were well to eastward of SCAMP, the enemy obviously having lost all trace of her. It was fortunate for SCAMP that no enemy surface ship sonar-listening searches were conducted in her vicinity for one of the results of the bomb damage was a very high machinery noise level.

9-15. Although not important, it is interesting to note that when a bottle of "Chlorox" in the crew's washroom was broken at about this time, the resulting small release of chlorine gas was thought at first to have come from sea water leaking into the after battery. Both battery wells were checked, however, and found to be dry.

9-16. SCAMP remained submerged until well after dark and then surfaced at 2103. Upon reaching the surface and blowing tanks, the ship assumed a 17 degree port list. The heeling moment responsible for this excessive list was due chiefly to the following two reasons: (a) the fuel oil in port FBT No. 5B had been displaced with heavier sea water while the fuel oil in the corresponding starboard tank FBT No. 5A had remained intact; (b) sea water in port MBT Nos. 4B and 6B could not be completely blown upon surfacing since the division bulkheads between these two tanks and FBT No. 5B had pulled away from the hull, allowing air introduced into any of the three tanks to escape through the rupture at the tank top of FBT No. 5B and also through a leaking emergency vent valve and riser of MBT No. 4B. On SCAMP, of course, the exact reasons for the list were at this time unknown. All possible variable ballast water was shifted to starboard tanks immediately but this reduced the list only slightly. The loss of fuel oil from FBT No. 5B was first discovered when test cock samples showed that tank to be full of sea water. It was then decided to remove the vent riser blank from the corresponding starboard FBT No. 5A and allow the oil therein to escape during a dive so as to equalize the liquid loading.

9-17. Meanwhile, and in spite of the excessive list, SCAMP started both starboard main Diesels and cleared the area by proceeding south, running on one engine and charging batteries with the other. Starboard fuel tanks were put on service to reduce list by increasing salt water ballast on the starboard side. Low pressure blowers were run every thirty minutes.

9-18. Two men were sent into the superstructure in an attempt to remove the FBT No. 5A vent riser blank. They managed to insert and secure a crowbar under the riser blank but when a trim dive was made, at 0102 (8 April), in an effort to displace the fuel oil, it was found that the opening was insufficient to allow this. Therefore, at 0137, SCAMP surfaced and again men were sent aft in the superstructure to remove the riser blank. After about three hours work, the task was finally accomplished and, at 0455, another trim dive was made. This time oil poured out of FBT No. 5A. By 0555, test cock samples showed the tank to be clear of oil so SCAMP surfaced. The list was now reduced to 9 degrees port. Both FBT Nos. 5A and 5B were left rigged as free flooding tanks.

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9-19. SCAMP's fighting effectiveness was reduced as the result of the attack to defensive action only. Although all torpedoes could be fired, further offensive action would have been inadvisable due to slow diving time, poor depth control, high noise level, and the decreased factor of safety at deep depths because of the hull damage. It was therefore decided to terminate the patrol at once.

9-20. SCAMP proceeded to Seeadler Harbor, Admiralty Islands, for temporary repairs and arrived there on 16 April 1944. From 10 April until arrival at Seeadler, SCAMP was escorted by DACE (SS247). Daylight hours were spent submerged during the entire run. Diving was slow and the boat was still somewhat difficult to handle submerged due to inability to maintain proper trim control. The return trip was uneventful except for numerous minor electrical casualties. Constant efforts were made by ship's force to stop leaks and repair damage where possible. The radio had been put out of commission due to a damaged coupling on the TBL motor-generator but satisfactory repairs were made by 10 April and communications were reestablished. On 11 April, a small fire started in the pump room air conditioning panel but this was soon brought under control and extinguished. On 14 April electrical power was lost on the bow planes for reasons not reported, but was restored within two hours. On 15 April a 190 volt ground developed in the after battery. Inspection revealed zero resistance grounds in three port cells, Nos. 106, 120 and 121, although it was reported that no loss of electrolyte occurred. These cells were by-passed and no further difficulty was experienced.

9-21. Damage to the superstructure is illustrated in Photos 9-2 and 9-3. The port superstructure deck and side plating were completely carried away in the vicinity of FBT No. 5B and the wood and steel decking was demolished or torn up across the width of the ship over a length of about ten feet. Aside from this immediate area, the only superstructure damage which occurred was minor distortion of the bridge fairwater plating and the bridge steps.

9-22. The tearing of the main induction line at the point of attachment of its welded supports (Photo 9-5) is an excellent example of the type of damage to be expected when a relatively non-rigid structure having a large area exposed to explosive loading, in this case the induction piping, is restrained from movement by welded attachment over small areas to relatively much stronger and more rigid members, in this case the bracket supports. The induction piping naturally tended to move bodily when struck by the shock wave from the bomb detonation, and was restrained only by its widely separated welded supports. The stress concentration at these points exceeded the ultimate shear strength of the pipe wall and consequently tearing resulted. A better design would have been one with small fillet welds, between the supports and the pipe, which would have failed before tearing the pipe walls. To prevent a recurrence of this casualty on SCAMP and other submarines, immediate replacement of all such directly welded supports on external induction and ventilation lines with non-welded belly-band type supports was

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authorized.1 The partial collapse of the induction piping between welded stiffening rings (Photo 9-6) illustrates the great effect such stiffeners have in increasing the collapse strength of circular pressure vessels. It should also be noted that the collapse occurred only on the side directly facing the bomb detonation.

9-23. Severe deformation was sustained by the upper portion of the outer hull plating and framing between frames 72 and 82, port, over a longitudinal distance of about 30 feet (Photo 9-4 and PLATE IX-1). Minor distortion occurred forward to frame 69 and aft to frame 85. Tanks in this area are MBT No. 4B, FBT No. 5B and MBT No. 6B. The maximum indentation in the outer hull plating was about 12 inches, occurring between frames 78 and 79 at the tank top of FBT No. 5B (Photo 9-3). The average indentations of other areas of heavy damage in the outer hull were between 4 and 7 inches.

9-24. The outer hull plating was ruptured in only one place, a two-foot longitudinal tear which occurred at the tank top of FBT No. 5B between frames 79 and 80 (Photo 9-7). This was caused by excessive stress concentration at the tank top knuckle due to structural discontinuity at the bracket connection scarfing the outer hull frame within the tank to the topside pressure hull frame outside the tank (See sketch in PLATE IX-1).2 The fact that only one rupture occurred in the outer hull although distortion of structure was severe, and even that one rupture being attributable to basic design, demonstrates the great ability of such welded structures to deform without loss of their watertight integrity.

9-25. The wing bulkheads at frames 75 and 80, extending from the inner to the outer hull and separating MBT No. 4B, FBT No. 5B and MBT No. 6B, were extensively buckled. Both of these bulkheads, together with their stiffeners, were torn loose from the inner hull, thereby intercommunicating all three tanks (Photo 9-10). This allowed fuel oil from FBT No. 5B to reach MBT Nos. 4B and 6B and prevented the complete blowing of the latter two tanks, since FBT 5B was torn at the top and thereby opened to the sea. Inability to blow these port tanks


1 Authorized by BuShips ltr. SS/S38-1(515-815) of 7 June 1944.
2 To diminish the possibility of this casualty occurring again to SCAMP or other applicable submarines, BuShips conf. ltr SS/S11-2(515) of 27 June 1944 authorized the modification of such bracket connections to reduce stress concentration under high explosive loading conditions. This was accomplished by installing a small reinforcing plate so as to lap the standing flanges of the pressure hull frames onto the tank tops instead of terminating them abruptly at the tank top knuckle as provided in the basic design. Priority was given to those frames in way of normal fuel and fuel ballast tanks. See sketch in PLATE IX-1.

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contributed to the large list assumed by SCAMP on surfacing. In addition, the flood valves for MBT No. 4B and FBT No. 5B were twisted off their seats.

9-26. The structural deformation which occurred in the inner or pressure hull of SCAMP was the most severe known to have been survived by any U.S. submarine during World War II. The pressure hull plating (27.5-pound medium steel) was dished in from frames 69 to 84, a distance of 37 feet. Average indentations in the worst areas were of the order of 4 to 5 inches with a maximum indentation of 7-1/8 inches occurring near the tank top margin plate at frame 79-1/2 (Photos 9-9 and 9-11). Graphical presentation of the pressure hull deformation over this area is included in PLATE IX-2. In no place was the pressure hull ruptured. Pressure hull frames (6" x 3-3/8" x 14.75-pound I-beams), secured to the hull with 5/16" fillet welds at the inboard flange toes, showed definite distortion throughout the areas of severe damage and in four places, frames 73, 74, 76 and 79, were torn from the inner hull when the latter dished inward (Photo 9-8). As mentioned above, tank bulkheads at frames 75 and 80 also were torn away from the inner hull (Photo 9-10). It is amazing that SCAMP's pressure hull retained sufficient strength to permit operation without collapse at a depth of about 330 feet subsequent to the damage.

9-27. Damage naturally was sustained by valves, fittings and piping systems attached to or passing through the pressure hull and outer tank boundaries in way of deformed areas, but was relatively minor considering the severity of the structural damage. MBT No. 4B vent riser leaked at the flanged connection with its tank top. Main vents

for MBT No. 4B and safety tank leaked. The emergency vent for MBT No. 4B also leaked and its operating gear was pulled out of line. Due to the extreme indentation of the pressure hull at that location, the emergency vent operating gear for FBT No. 5B was bent 45 degrees out of line and forced in hard against the scavenging blower of No. 2 main engine (Photo 9-12). This vent valve was later opened by cutting a hole in the tank top. The 3000-pound high pressure air line leading from the air flasks in MBT No. 4 was bent between the inner hull and the hull stop valve but no leakage resulted either here or anywhere else in the entire high-pressure air system, although external air banks were subjected to considerable explosive loading in way of the damage. A fuel oil transfer line and a fuel oil compensating line inside the pressure hull abreast FBT No. 5B were bent and twisted but did not leak. Although hydraulic lines in the forward engine room were bent, there were no hydraulic leaks anywhere in the boat. Minor leakage occurred at a fresh water line fitting in the crew's washroom but this was easily repaired. Perhaps the most serious piping casualty was the flattening of the No. 2 sanitary tank overboard discharge line which prevented blowing the tank. This discharge line also leaked at its flanged seachest connection to the outer hull in way of MBT No. 4. The

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seat of the forward engine room air induction hull valve was slightly distorted and allowed considerable water to enter the compartment from the flooded induction piping topside. This leakage was later reduced by taking up hard on the valve with a chain fall.

9-28. Damage to machinery was surprisingly minor considering that the detonation occurred abreast the forward engine room. The scavenger blower for No. 2 main engine was misaligned, possibly by shock but more probably as a result of the inward bulge of the pressure hull pushing the operating gear of FBT No. 5B emergency vent valve into the blower housing (Photo 9-12). No attempt was made to run No. 2 main engine after hearing noises in the scavenging blower spiral impellers when the engine was jacked over. No. 3 main engine blower also sustained minor misalignment of the drive gears but this was not serious enough to prevent operation of the engine. No. 1 detached fuel oil pump was deranged so that it would not supply proper pressure but the exact nature of this casualty was not reported. No. 1 lubricating oil purifier was thrown out of alignment. No other damage, except for minor electrical derangements, occurred to auxiliary machinery anywhere in the boat. Machinery piping damage was limited to a ruptured line from No. 2 main engine exhaust to the compensating system.

9-29. Electrical damage, although in itself quite minor, had very serious effects on ship control due to the generation of toxic smoke by the small electrical fire in the maneuvering room. This fire was limited to a small rotary clutch by-pass switch (BuShips Standard Plan 9-S-4474-L) in the No. 4 generator field circuit of the main control cubicle. This switch was mounted in a closed phenolic frame and the burning of only a small portion of this phenolic material created the large volume of dense smoke (Photo 9-13)1. No report is contained in any of the references as to the cause of the fire but the following hypothesis is believed to be a plausible explanation. With the type of General Electric control cubicle installed on SCAMP, it was not necessary to clear the generator connections before shifting propulsion motors to battery power.2 Therefore, during quick dives, it was the custom with such propulsion controls to first change to battery power and then to de-energize all generator circuits. It appears probable that some metallic object, dislodged by the shock, fell through the cubicle and momentarily shorted the excitation supply to the No. 4 generator field. This would cause excessive current to flow through the clutch by-pass switch, which is used to by-pass the regular excitation contactors when two or more generator field rheostats are clutched together. The excessive current would cause the switch to arc and could account for the ignition of its phenolic case. Failure of this switch on SCAMP also short-circuited the Nos. 2 and 4 generator field supply and return leads and the port motor electrical interlock. Actually, both the port and starboard propulsion plants were undamaged and could have been kept in continuous operation. All power was cut off by ship's force, however, when smoke and flame were seen to issue from the control cubicle since it was quite correctly felt that the circuits should be checked through to


1 For further discussion, see paragraph 19-13.
2 Current General Electric Co. submarine propulsion control designs are provided with interlocks which require all generator connections to be opened before shifting to battery power.

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determine the nature of the casualty in order to prevent possible further damage to the motors and control equipment. Upon completion of this check, which took about 15 minutes due to the presence of the toxic smoke, the starboard plant was started simply by operation of the controllers and shortly afterwards the port plant was started in similar manner after resetting the electrical interlock by hand. With the exception of the fire in the clutch by-pass switch, there was no apparent misalignment, distortion or maloperation of any part of the control cubicle. It is interesting to note that the battery tank contactors did not open, although those in the after well had not been by-passed.

9-30. Auxiliary and lighting power were not lost at any time. Numerous clips holding cables to bulkheads were jarred loose in the forward engine room and crew's washroom. Only one battery ventilation duct fractured and this occurred in the after battery compartment. In the forward battery compartment, the battery fresh water tanks shifted forward about two inches. Damage to the batteries themselves was limited to the three cells having full grounds mentioned in paragraph 9-20 above. The forward battery air flow meter would not function, apparently due to a clogged or crushed line. The supply ventilation blower panel in the port side of the forward engine room was disabled and all leads were pulled loose. The ship's force later constructed a jury rig to provide power to this blower. The hot water heater panel located in the crew's washroom was completely wrecked when it was crushed against the hot water tank by the inward movement of the pressure hull in that area. Although galley equipment was damaged, also by dishing of the pressure hull, no grounds occurred in electrical circuits.

9-31. A moderate amount of damage occurred to electronic equipment and associated gear. The SJ radar antenna mast was slightly sprung but could be trained. Numerous tubes in the SJ receiver indicator were jarred loose and the feeder unit dipole sleeve was bent, causing a fluctuating pulse during antenna train. One tube in the SJ oscillator converter was broken and the lobe switching circuit was inoperable for reasons not reported. In spite of the above difficulties, repairs were made and the SJ radar was placed back in commission. The antenna coupling gap on the BN radio transmitting and receiving gear closed under impact, causing a high voltage arc. As mentioned previously, the coupling on the TBL radio motor generator jarred loose but was subsequently repaired and radio communications were restored. The forward insulator on the center radio antenna topside fractured and this antenna had to be cut down upon surfacing. The 1MC general announcing system could not be operated due to derangement of both signal generators.

9-32. Other miscellaneous items of damage not covered elsewhere are listed below. The gyrocompass repeater located on the bridge was knocked out of its gimbals and was suspended only by its electrical cable lead but still continued to function. The valve stem extension arm on the 10-pound blow stop valve for MBT No. 2B forward was found to be missing. Although the outside temperature element on the bathythermograph was torn loose, this equipment remained operative.

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9-33. At Seeadler Harbor, Admiralty Islands, repair forces from TANGIER (AV8) and JENKINS (DD447) patched the tear in FBT No. 5B, cleared away the superstructure wreckage, installed a new temporary superstructure, and placed No. 4 engine and generator back in commission. SCAMP departed Seeadler Harbor on 20 April for Milne Bay, New Guinea, arriving on 22 April 1944. Here she was docked in the ARD9 and temporary structural repairs were made to the bulkheads and frames which had been torn from the pressure hull.

9-34. SCAMP then returned to U.S. Naval Drydocks, Hunter's Point, arriving on 18 May 1944. Complete war damage repairs (Photo 9-14 and 9-15) together with routine overhaul and outstanding alterations were accomplished there and SCAMP was returned to service on 8 September 1944, five months after the action occurred.

9-35. SCAMP was lost on her next war patrol. Information made available by the Japanese upon termination of the war indicates that she was probably sunk while on lifeguard duty off Tokyo Bay as the result of one or more of three depth charge and depth bomb antisubmarine attacks conducted in her area during the period 11 to 16 November 1944. In the seven patrols completed before her loss, SCAMP was officially credited by ComSubPac with sinking six ships totaling 49,000 tons (2 AK, 2 APK, 1 SS, 1 AO) and damaging eight other ships totaling 40,400 tons (2 AK, 2 AO, 1 DE, 1 AP, 1 CA, 1 trawler).

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Photo 9-1: SCAMP (SS277). Preparing to tie up alongside TANGIER (AV8) in Seeadler Harbor, Admiralty Islands, on 16 April 1944. Note that port list has been reduced to about 5 degrees.

Photo 9-2: SCAMP (SS277). Bomb damage to superstructure. Alongside TANGIER (AV8), Seeadler Harbor, Admiralty Islands.

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Photo 9-3: SCAMP (SS277). View from port side, showing bomb damage to superstructure. No structure has been removed yet. Diver with shallow water rig is preparing to make an inspection. Alongside TANGIER (AV8), Seeadler Harbor, Admiralty Islands.

Photo 9-4: SCAMP (SS277). Bomb damage to outer hull, port side. View taken in ARD9, Milne Bay, New Guinea. Note temporary superstructure installed by TANGIER (AV8).

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Photo 9-5: SCAMP (SS277). Close view showing typical tear in engine air induction piping at welded bracket support. Tears occurred at four points between frames 75 and 78, causing rapid flooding of entire induction system.

Photo 9-6: SCAMP (SS277). View of port side, looking down and aft, showing partial collapse of the engine air induction piping. Note that stiffeners maintained circularity although the pipe shell collapsed between.

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Photo 9-7: SCAMP (SS277). Close view, looking down at tank top of FBT No. 5B, showing two-foot longitudinal tear which occurred at a point of stress concentration in the knuckle between the tank top margin plate and outer hull. About 7000 gallons of fuel oil escaped through this tear.

Photo 9-8: SCAMP (SS277). View from inside MBT No. 4B showing frames 73, 74 and the tank wing bulkhead at frame 75 torn away from the pressure hull.

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Photo 9-9: SCAMP (SS277). View from inside FBT No. 5B, looking upward. Bulge in pressure hull shown here between frames 79-80 was the maximum sustained (7-1/2 inches deviation from true circle). Note temporary repairs to wing bulkhead 80, accomplished while in ARD9 at Milne Bay. Valve shown is the emergency vent valve for FBT No. 5B.

Photo 9-10: SCAMP (SS277). View from inside MBT No. 6B, looking up and forward. Wing bulkhead 80 and radial bulkhead stiffeners torn away from pressure hull. This breached MBT No. 6B into FBT No. 5B and thence to the sea through the tear in FBT No. 5B tank top (Photo 9-7).

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Photo 9-11: SCAMP (SS277). View of bulges in pressure hull as seen from inside the forward engine room, port side, looking forward.

Photo 9-12: SCAMP (SS277). Close view showing displacement of FBT No. 5B emergency vent valve due to bulge in pressure hull. Contact of valve operating mechanism with No. 2 main engine scavenging blower housing caused damage to the spiral impellers of the blower and disabled No. 2 engine.

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Photo 9-13: SCAMP (SS277). Full size view showing phenolic case of No. 4 generator field circuit clutch by-pass switch in propulsion control cubicle. Burning of this material was the sole source of dense toxic smoke which filled maneuvering room. Note the small amount of phenolic material which was actually consumed.

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Photos 9-14 and 9-15: SCAMP (SS277). Two views showing reconstruction of damaged portion of ship at U. S. Naval Drydocks, Hunter's Point. Note positioning "spiders" for pressure hull shell plating.

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Plate IX-1: Depth Bomb Damage

Plate IX-1: Depth Bomb Damage


SECTION X

U.S.S. TANG (SS306)

Loss in Action

Formosa Strait

24 October 1944

Class

SS285

Builder

U.S. Navy Yard, Mare Island

Commissioned

November 1943

Length (Overall)

311 ft. 8 in.

Beam (Extreme)

27 ft. 3-1/4 in.

Submergence Depth (Designed Maximum) (Axis)

400 ft.

Displacements

Standard

1525 tons

Emergency Diving Trim,

1956 tons

Submerged

2408 tons

Draft (Mean, Emergency Diving

16 ft. 2 in.

Type of Propulsion

Diesel Electric Reduction Drive

Main Engines (4)

Fairbanks-Morse 38-D-8-1/8

Main Motors (4) and Generators (4)

Elliott Co.

References:

(a) C.O. TANG conf. ltr. SS306/A-16-3 of 10 September 1945 (Report of War Patrol Number Five and Loss of Vessel).
(b) BuMed conf. ltr. BLK:II, Serial No. 0356 of 29 July 1946 (Submarine Escape in World War II).
(c) Interviews with Various TANG Survivors by Cdr. I. F. Duff, (MC), USNR.

Photograph No. 10-1 (Torpedoing of U-977 - Associated Press) and 10-2. PLATE X

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10-1. On 24 October 1944, during her fifth war patrol, TANG was sunk in Formosa Strait as a result of the malfunctioning of one of her own torpedoes which made a circular run and returned to strike the hull abreast the after torpedo room.1 The resulting detonation caused the ship to plunge by the stern within a few seconds.

10-2. This report is based on the information contained in the references. The first portion of reference (a) is a narrative of TANG's fifth war patrol up to the time of her loss and was written from memory by the Commanding Officer upon his release from a Japanese prisoner of war camp at the end of the war, approximately one year after the action took place. The second portion of reference (a) is a reconstruction of the events which occurred in TANG after the torpedo struck. Since the Commanding Officer was washed off the bridge when the ship sank, this portion is based on the stories of the eight other survivors as related to him at the first opportunity after their capture by the Japanese; five of the eight having gone down with the boat and later making individual underwater escapes from the forward torpedo room. This reference, although understandably not as complete as formal war damage reports covering actions in which a submarine returns to base and damage can be thoroughly investigated, is an excellent presentation of the available data and is the only account in U.S. Naval history of the events inside a war-damaged U.S. submarine during and after its sinking. References (b) and (c) cover the escape problem facing the men trapped within the boat and the procedure used by those few who made successful escapes. These latter two references are based upon personal written and oral accounts of the survivors as related to representatives of the Bureau of Medicine and Surgery. The photograph of the torpedoing of U-977 is included to illustrate the magnitude of TANG's disaster. The PLATE was prepared by the Bureau.

10-3. The fifth war patrol of TANG was conducted in the Formosa Strait. This area was assigned in order that TANG would be in a position to intercept any Japanese shipping which might retire from Formosa as a result of the carrier strikes against that Island by the Third Fleet on 12 through 14 October 1944, and also to intercept any enemy reinforcements which might pass through Formosa Strait in support of the Philippine campaign which commenced with the Leyte Island landing on 20 October 1944.

10-4. After normal refit at the Submarine Base, Pearl Harbor, TANG departed for Formosa Strait via Midway on 24 September 1944 and reached her patrol area on 10 October. On 11 October TANG sank one large and one medium-sized cargo ship off the west coast of Formosa, the first by a dawn torpedo attack while submerged and the second by a night torpedo attack while surfaced. On 12 through 14 October, the period of the Third Fleet air strikes against Formosa, numerous searches were conducted along likely enemy shipping retirement lanes


1 There is evidence to indicate that the loss of TULLIBEE (SS284) on 26 March 1944 was similarly caused by a circular run of her own torpedo. See Appendix II.

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to the China coast but no contacts were established. From 14 to 22 October, although several enemy ships were sighted, range to the targets could not be sufficiently closed and consequently no attacks were made. Shortly after midnight on 22 October, radar contact was established with a heavily escorted enemy convoy composed of three large tankers, a large cargo ship, and a medium-sized transport. All ships were heavily loaded and were apparently bound for support of the Philippine campaign. TANG executed a spectacular close range night surface attack, sinking all five ships of the convoy within ten minutes of firing her first torpedo and then cleared the area at full speed, leaving the escorts apparently engaged in a gun duel with one another.

10-5. Following the action of 23 October, TANG proceeded north of Formosa Strait for deeper water and then headed toward the shallow protected waters along the China coast on the theory that, due to her recent successes, all subsequent Japanese shipping passing through the Strait would be routed close inshore. This belief proved correct, for in the early evening of 24 October radar contact was established with a large Japanese convoy hugging the China coast and located about midway between Foochow and Amoy. The convoy was proceeding south at a speed of about twelve knots, apparently also headed for the Philippines, and consisted of at least fourteen large, heavily-loaded ships in column escorted by at least one destroyer and twelve destroyer-escorts. Some of the escorts were to seaward of the convoy while others were on the landward side.

10-6. TANG closed for a night surface attack using radar ranges and TBT bearings, but her presence was apparently suspected for two of the seaward enemy escorts commenced to run on opposite course to the convoy column, firing sporadic and wild bursts of small and medium caliber projectiles. As TANG continued to approach, one of the enemy escorts illuminated the convoy column with a large searchlight while signalling and this had the favorable effect of increasing target ship visibility. Three of the leading ships, a large transport, a medium-sized transport and a large tanker, were selected as the initial targets and, at ranges varying from 900 to 1400 yards, TANG fired three slow deliberate salvos of two torpedoes each per ship. In spite of the enemy having had apparent early knowledge of TANG's presence, no evasive tactics were employed by any of the ships up to this time. All torpedoes ran true to their targets, sinking the three ships almost immediately. Meanwhile, TANG paralleled the convoy to search out the next two targets. A tanker and a transport were selected for stern torpedo attack and three torpedoes were fired at ranges between 600 and 700 yards. The escorts had now stopped their warning tactics and were directing close salvos at TANG. Just after firing at the transport, a destroyer crossed close to the stern of that ship and headed directly for TANG. The first torpedo hit the tanker, which was apparently loaded with gasoline, and a tremendous explosion resulted. The second torpedo was observed to hit the transport and an instant later the destroyer blew up, either intercepting the third torpedo or cross fire from two enemy escorts which were bearing down on TANG's beam. Only the transport remained afloat and she was apparently stopped dead in the water.

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10-7. TANG cleared the immediate area at flank speed, still on the surface and untouched by the enemy gunfire. When 10,000 yards distant from the enemy escorts, a halt was made to survey the situation and to recheck the last two torpedoes remaining on board. About one hour was spent on this work, the torpedoes being partially withdrawn from their tubes, batteries ventilated, gyros inspected and the steering mechanism observed to be operating freely. The two torpedoes were then reloaded in forward tubes Nos. 3 and 4 and TANG commenced a cautious approach to again attack the crippled transport, which was now observed to be lower in the water but definitely not sinking. Since two enemy escorts were patrolling to seaward of the transport, TANG made a wide sweep and came in very slowly to escape detection by sonic listening gear. Upon reaching a favorable position, the twenty-third torpedo was fired at the transport from a range of about 900 yards. Ship speed at this time was about six knots and the heading was conned for zero gyro angle setting on the torpedoes.

10-8. When the phosphorescent wake of the twenty-third torpedo was observed heading true for its intended point of aim on the target transport, the twenty-fourth and last torpedo was fired. This torpedo assumed an erratic course immediately upon leaving its tube and curved sharply to the left in a tight turning circle, broaching during the first part of its turn and porpoising during the remainder.1 Due to the phosphoresence of its wake, the torpedo was observed through 180 degrees of its turn. As soon as the erratic behavior was noted, which was almost immediately after the torpedo was fired, TANG went to emergency speed and partially executed a fishtail maneuver in a futile effort to clear the turning circle. This resulted only in the torpedo striking the boat farther aft than would have been the case had no evasive action been taken. The twenty-fourth torpedo, as were all those carried by TANG on this patrol, was an electric-driven Mk. 18, Mod. 1, fitted with a Mk. 18, Mod.1 warhead containing 570 pounds of TPX (equivalent in damaging effect to approximately 850 pounds of TNT).

10-9. The torpedo struck TANG on her port side aft in the vicinity of either the after torpedo room or the maneuvering room, about twenty seconds after being fired. The exploder mechanism (Mk. 8) used in the Mk. 18, Mod. 1 torpedo warhead is an inertia type which fires by impact from any angle and the time delay between receiving an impact blow and detonation of the warhead is so slight that the fuzing may be considered as instantaneous. It is therefore probable that the torpedo detonated on contact with the outer hull if it struck in way of the maneuvering room or with the single hull (pressure hull) if it struck in way of the after torpedo room. The Mk. 8 exploder mechanism arms itself by an impeller driven gear train, the impeller being caused to revolve by the ahead motion of the torpedo through the water. Arming of a Mk. 18 torpedo at its rated speed of about 29 knots should normally occur in approximately 200 yards or about 12 seconds running time. Based on studies of torpedo war damage experience with surface vessels, it is estimated that the torpedo detonation probably caused complete destruction of a section of TANG's pressure hull extending


1 A torpedo anti-circular-run device is currently being developed by the Bureau of Ordnance to prevent recurrence of such malfunctioning.

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over a longitudinal distance of at least 25 feet on the port side and extending in depth almost through to the opposite side of the hull, if in fact the hull itself was not completely severed (Photo 10-1).

10-10. Sufficient information is available to permit a fairly complete description of the events which occurred in TANG following the detonation. The boat as a whole was violently whipped. One survivor (conning tower) stated: "With the explosion of the torpedo, the boat seemed to bounce up and down". Personnel as far forward as the control room sustained broken limbs and other injuries. Pipe lines fractured, deck plates lifted up and lightly attached fittings and loose gear were flung about. The propulsion plant was destroyed instantly and men watching the pitometer log in the forward torpedo room noted that the boat lost all forward motion within a few seconds. The after torpedo room, maneuvering room, after engine room, and probably all adjacent tanks flooded rapidly. The watertight door in the after bulkhead of the forward engine room was closed with difficulty against the inrushing water from the after engine room, but not until the forward engine room had been half flooded. There were no survivors from the three after compartments. The ship apparently settled slowly for a few seconds and then plunged rapidly by the stern. Reference (a) states that "TANG sank by the stern much as you would drop a pendulum suspended in a horizontal position". Three of the nine officers and men on the bridge were thrown clear or were washed over the side as the boat sank and managed to stay afloat until rescued by the Japanese about eight hours later. Nothing is known of the fate of the other six men on the bridge. No lookouts survived and it is possible that they may have been unable to extricate themselves from or were injured by the periscope shear guard rails and were carried down with the ship. Communications were maintained between the conning tower and bridge until the ship plunged but there was insufficient time to carry out an order to close the upper conning tower hatch. Water poured through this open hatch and completely flooded the conning tower within a matter of seconds after it went below the surface of the water. One officer subsequently made a successful underwater "free" escape from within the flooded conning tower and it is known that one man was thrown through the lower conning tower hatch into the control room by the shock of the detonation, breaking his arm in doing so. Personnel in the control room succeeded in closing the lower conning tower hatch to prevent the inrush of water into the lower compartment. The hatch had been damaged, however, and leaked badly, causing the control room and pump room to flood slowly.

10-11. Although TANG's stern plunged to the bottom, the buoyant force of the intact amidships and forward compartments and tanks was such that the bow remained on the surface, the boat assuming a "spar buoy" position with an up angle of approximately 40 degrees. The officer who escaped from within the conning tower stated that upon reaching the surface he observed about 25 feet of the bow projecting above water. Within the ship, all loose gear fell to the after ends of each compartment and all hands held onto anything they could grasp. Some lost their footing and were thrown aft.

10-12. The men in the forward torpedo room, about ten in number, had secured their compartment shortly after the detonation occurred

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and after vainly attempting to contact other compartments by phone came to the conclusion that the after part of the ship was destroyed. They discussed the possibility of escaping at once through the empty forward torpedo tubes but decided against that course because they could hear depth charges and feared the bow would be shelled.1

10-13. Personnel in the control room had also secured their compartment immediately after the detonation but possessed somewhat more complete information as to the extent of damage. Their prompt execution of damage control measures had established boundaries sufficient to prevent further rapid intake of water and they realized that some of the men trapped within the boat might be able to escape through the one remaining intact escape trunk in the forward torpedo room. To prevent the possibility of damage to the exposed bow by enemy action, and to facilitate escape operations by removing the excessive up angle, it was decided to sink the bow and level off. Therefore, about fifteen minutes after the initial damage occurred, TANG was deliberately bottomed by flooding the No. 2 group of main ballast tanks. Hydraulic power not being available, flooding of these tanks was accomplished by manual operation of the vent valves in the overhead of the control room.

10-14. Meanwhile, classified publications were being destroyed by burning, at first in the control room and later in the forward battery compartment when the water level in the control room made it necessary to evacuate and seal that space. The survivors from the control room and forward battery compartment, about fifteen men in all, then proceeded to the forward torpedo room, carrying their injured in blankets. When the door to the forward torpedo room was opened, the difference in air pressure between the two compartments due to leaking air systems amidships was such that those men near the door were literally blown into the torpedo room.

10-15. About one-half hour later, the survivors from the forward engine room and after battery compartment decided to attempt to reach the forward torpedo room. This group consisted of about twenty men, two of whom were injured. They discovered by peering through the


1 Based on the reports that TANG assumed a 40 degree up angle with about 25 feet of the bow exposed, the outer doors of the torpedo tubes would have been slightly below the surface of the water at this time and escape through the tubes would therefore have been difficult, if not impossible. There are two instances, however, where such escapes have been accomplished from U.S. submarines. (1) S-5 sank in 194 feet of water off the Delaware Capes on 1 September 1920, due to internal flooding through maloperation of the induction valve. The crew managed to blow the stern to the surface and with great effort cut a small hole in the shell above the waterline. All hands were released about 51 hours later when an escape access was cut in the exposed stern by the crew of the steamship GENERAL GOETHALS. (2) On 7 December 1921, S-48 sank in 67 feet of water while on trials off Bridgeport, Connecticut. The engine room, motor room and steering room were flooded due to neglecting to replace a manhole cover on No. 5 port ballast tank. The bow was blown to the surface and all 41 men aboard escaped through a torpedo tube.

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eye-port in the watertight door to the control room that water in that space had already flooded above the door level. On testing the bulkhead flappers in the ventilation piping they found the water not yet at this height. They therefore opened the bulkhead door, letting the water race through, and then proceeded to the forward torpedo room. When these men first attempted to open the door to the torpedo room, two men in the torpedo room tried to get them to crack the door slowly so as to gradually equalize the large difference in air pressure between the two compartments. The men in the forward battery compartment, however, did not understand the signals and thought they were being deliberately kept out. They forced the door open and, being accelerated by the air pressure, it struck and severely injured one of the men in the forward torpedo room who had been trying to signal to them.

10-16. All of those men who had survived the initial damage, a total of about forty-five, were now in the forward torpedo room. When the last group arrived, about one hour after TANG first plunged, it was learned that the boat was flooded to the forward engine room. The general feeling of the men at this time seems to have been one of mixed optimism and confidence in their ability to eventually escape combined with excitement and lack of direction. From the last radar bearing, they knew they were only a few miles offshore and it was therefore felt that the chances of reaching land after ascending to the surface were quite favorable. They also had a fairly accurate estimate of the depth of the water from the angle the boat assumed when the stern sank and also from previous chart and fathometer soundings. Submarine escape devices, or "lungs" were passed to all hands and instructions on how to use them were reviewed. Over half the men seemed to possess but little familiarity with the operation of the "lung" equipment. The limited number of available life jackets were distributed and those without were instructed to use their "lungs" as such when they reached the surface. The atmosphere within the forward torpedo room at this time was fairly good, although some smoke and fumes had been introduced from the burning of the classified material. Heat and humidity were increasing and the higher than normal air pressure due to accumulated air leakage caused some discomfort, but adverse physiological effects were not yet pronounced. Although the ship's service lighting system had failed a few minutes after the detonation, the emergency lighting system was functioning properly.

10-17. Preparations for escape were halted when, at about this time, several depth charges were dropped close enough to shake the boat considerably although no further damage was sustained. The enemy remained in close proximity for the next several hours and during this period all activity in TANG came to a standstill. Meanwhile, a fire, reported by reference (a) to have been of electrical origin, started in the forward battery compartment and became quite intense.

10-18. When the enemy vessels apparently had finally departed, it was decided to first attempt to blow tanks and flooded compartments to see if the boat could be surfaced, and thereby render it much easier and quicker for all hands to escape. A small party of men was

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assembled to proceed to the control room on this mission but when they started to open the watertight door to the forward battery compartment, large quantities of acrid black smoke from the fire in that space blew into the torpedo room. Although the door had been cracked for only a second or two and then closed at once, fumes and smoke completely filled the compartment. Visibility was reduced to the extent that the lights could be but dimly discerned. Some of the men began to gag and suffered considerable distress almost immediately. The smoke was reported as having an odor similar to that of burning rubber. It is quite likely that the batteries themselves may have been on fire since it was stated that the disconnect switch for the forward battery had not been opened and numerous short circuits are known to have existed. When irritation from the smoke became severe, many men used their "lungs" as respirators, apparently with considerable success. The men were now trapped by the forward battery compartment fire and since self-salvage efforts, at least to the extent of once again raising the bow to the surface, could not be made, there remained no alternative but to attempt individual escapes.

10-19. The first escape attempt was made shortly after daylight. A party of one officer and three men equipped with "lungs" entered the escape trunk, flooded it and opened the side door. It had been arranged that the last man to escape was to notify the men below by tapping just before he left the trunk so that the door could then be closed and the trunk drained down to make ready for the next party. However, due to difference of opinion as to how the trunk operated and difficulty in rigging the ascending line and escape buoy, an inordinately long period of time was consumed. The officer left the trunk before the ascending line and buoy had been streamed and was never seen again. The remaining three men finally completed rigging the escape line but by this time approximately forty minutes had elapsed and the personnel below in the torpedo room, having received no signals from the escape party, closed the trunk door by the remote operating gear and drained the trunk down, thus preventing the escape of the men within.

10-20. A second party of three men and two officers then entered the trunk and rigged for escape. Three of this group left the trunk, one of whom reached the surface alive and survived. The other two who left the trunk were not seen again. After another forty minutes or so, again having received no signals from the escape party but hearing moans from within the trunk, personnel below in the torpedo room closed the escape door, drained the trunk and found the remaining two members of the party, both officers, still in the trunk. One was in a semi-conscious condition, presumably due to inability to withstand the high partial pressures and increased carbon dioxide content of the atmosphere within the trunk. The other officer had become fouled in the unused portion of the ascending line which, after having been cut inboard of the point of attachment of the buoy line outside the trunk, was withdrawn into the trunk and apparently loosely piled underfoot. However, it was the belief of the men below that the line which fouled the officer was the buoy ascending line itself and that the buoy had been cut free outside the door.

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10-21. The difficulties encountered in these first two escape attempts combined with the presence of the smoke and progressive deterioration of the atmosphere within the torpedo room had by this time noticeably lowered the morale and physical condition of all hands. All former enthusiasm now died down and many of the men did not care whether they escaped or not. One of the survivors stated: "The constantly increasing pressure, smoke, and heat seemed to affect everyone's thinking". Another survivor stated: "Difference of opinion among the first men attempting escapes wasted valuable minutes. The men weren't sure of escape procedure and were afraid they would make a mistake that would be fatal to the men below. Escape procedure is very simple on paper but somewhat different where everyone's life depends on it. One of the major difficulties encountered was the lack of proper means of communication between the men in the trunk and the men below. We didn't know what was going on or what troubles they had". One of the officers who was in the second party to enter the trunk but was unable to escape and returned below, was apparently one of the few men aboard who had made a one hundred foot training escape. He is reported to have stated that although he personally did not care to attempt to escape again, there was no reason why all of the others should not be able to escape.

10-22. A third party, consisting of four men, then entered the escape trunk. They carried with them a lifering and line with the idea of streaming it for use as a new ascending line since, as previously stated, it was their belief that the original escape buoy had been cut adrift by the second escape party. After flooding the trunk and opening the door, it was found that there was no oxygen available at the trunk manifold with which to initially charge their "lungs". Although aware that the "lungs" could be blown up with their own breath sufficiently to permit safe ascent, only one of the four elected to do so. It took about fifteen minutes to rig the trunk, including preparing the lifering as a buoy, and by this time the one man intending to escape, although having no difficulty with breathing through his "lung", had become very exhausted and dizzy. He had planned to let the lifering go up to the surface and then to ascend the line attached to the lifering as in the standard escape buoy rig but, being on the verge of passing out, he simply stepped out of the trunk, holding the lifering in his arms, and started rapidly toward the surface. One of the men who remained in the trunk tried to slow down this fast ascent by jerking on the line as it payed out but this caused the escaping man to lose use of his "lung" after going up about twenty feet. From that point up he made a "free" escape by allowing the constantly expanding air in his lungs to vent through his open mouth, reaching the surface alive and in sufficiently good condition to remain afloat until rescued. The men remaining in the trunk then drained the space and obtained more oxygen for the "lung manifold from the torpedo room. Two of these men were so completely discouraged that they refused to

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obtained more oxygen for the "lung" manifold from the torpedo room. Two of these men were so completely discouraged that they refused to try again. The one and only man who escaped on this third attempt was familiar with the escape procedure through adequate previous training. He stated, "I felt at ease using the "lung" and knew it would work after I tested it under the water before leaving the trunk. I had made a one hundred-foot escape before".

10-23. After another forty-five minutes or so, three men from a fourth escape party reached the surface alive using "lungs" and, although exhausted, managed to stay afloat. Approximately one hour later, three others from the fifth and last known escape attempt reached the surface but were in weakened condition, apparently unable to breathe, and died shortly afterwards. At least one of the men is believed to have died as a result of air embolism.

10-24. Of the thirteen men who are known to have left the submarine via the escape trunk, only eight are known to have reached the surface and of these eight only five were in sufficiently good condition to cling to the buoy until rescued. Some of the men who were not seen again after leaving the trunk may have reached the surface alive but perhaps did not use the ascending line and were carried by currents to points out of sight of the group at the escape buoy and subsequently drowned. Conditions inside the trunk when being flooded by the various escape parties were no doubt partially responsible for the low percentage of successful escapes. One survivor reported "The compression of the air as the water flooded the trunk caused a great amount of heat. When the water was above the door, it left a very small air space and everyone had difficulty in getting their breath. The pressure made the voices very high and almost inaudible. All these combined to create a certain amount of panic in everyone".

10-25. The exact fate of the thirty odd men who remained in the forward torpedo room is not known although it is quite apparent that the viability of the atmosphere in the forward torpedo room was probably soon reduced below the point at which life could be sustained. The deleterious effects on all hands of the smoke introduced from the forward battery compartment was considered by the survivors to have been one of the greatest factors in delaying and hindering the escape attempts. One survivor stated "This smoke did more to kill the men who didn't get out than any other thing". Another stated "The smoke undoubtedly killed every man in the compartment not long after the Japs picked us up. Some men were nearly unconscious when I left. The smoke made you cough and the coughing caused more irritation in your lungs and throat". Heat and humidity reached high levels and air pressure kept increasing due to leakage through forward battery compartment drains into the No. 1 sanitary tank and thence into the forward torpedo room through the lavatory drain. The leakage occurred in spite of check valves in the lavatory line and use of wooden plugs provided in the depth charge kit. In addition to causing considerable discomfort in itself, the increase in air pressure in the forward torpedo room also accelerated the physiological effects of the smoke and whatever other noxious or toxic gases that may have been present, such as carbon monoxide.

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10-26. Increase in CO2 content was reported as not being too noticeable because of the amount of smoke in the air although this component must have been present early in dangerous quantity. Though use of CO2 absorbent was considered, it had not been employed up to the time the last survivor escaped since the large number of men in the compartment left but little area to spread the chemical. Lack of use of CO2 absorbent was a serious error for calculations indicate that, with 45 men in the forward torpedo room, a 3 per cent CO2 concentration would have been reached in only four hours. The effect on personnel of excessive CO2 was also enhanced by the rise in air pressure known to have occurred in the compartment.1 CO2 poisoning is believed to have been the most important single factor causing the early debilitation of the crew and alone could have been responsible. Oxygen was bled into the compartment several times to revitalize the air and seemed to relieve the general feeling of suffocation.

10-27. When the fourth and last successful escape party entered the escape trunk, the fire in the forward battery compartment was reported to have reached such intensity that paint on the forward side of the torpedo room bulkhead had melted and was running down. Considerable pressure had built up in the forward battery compartment and apparently the bulkhead door was not sufficiently tight to prevent acrid smoke from seeping by the gasket. Reference (a) advances the theory that this door gasket may have blown out, either due to pressure or an ensuing battery explosion and that the remaining personnel were thereby asphyxiated. Aside from from this conjecture, however, the members of the fourth escape party believed that at the time they entered the escape trunk the breathing conditions in the torpedo room had deteriorated to such an extent, due to increased air pressure, lack of oxygen, high carbon dioxide content and the presence of fumes and smoke, that all remaining personnel would probably have been rendered unconscious or dead within a very few hours.

10-28. All of the total of nine men who survived, five from the escape trunk, three from the bridge and one from the conning tower, were picked up during the day by one of the Japanese escorts. One consolation to the survivors was the sight of the bow of their last transport target projecting out of the water a thousand or so yards away.

10-29. The unaided "free" escape of the only survivor from within the conning tower is interesting. As the stern plunged toward the bottom and the conning tower flooded rapidly through the open upper hatch, this officer held onto the No. 2 periscope tube for support. He at first obtained air by pressing his mouth up into the periscope stuffing box structural housing recess at the top of the conning tower, where a small bubble of air had been entrapped, and then swam underwater to the forward end of the conning tower where, due to the extreme up angle of the boat, a fairly large bubble had pocketed between the forward bulkhead and the conning tower hatch. Figuring that he might be able to reach another air bubble topside, he then swam up through the conning tower hatch and found an air pocket trapped under the pilothouse


1 See paragraph 22-15.

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front and the officer-of-the-deck's bridge platform. After pausing momentarily in this bubble, and knowing that it was perfectly feasible to make an ascent without the aid of a "lung", the officer began to swim up as rapidly as he could, expelling air all at one time when part way up, and burst out on the surface just as he thought he would have to inhale some salt water. The bridge deck at this time was about fifty feet below the surface. Of the other eight men in the conning tower, one fell into the control room through the open lower hatch, as stated previously, and a second man is known to have also reached the air bubble trapped under the pilothouse but did not reach the surface. The remaining six men were either rendered unconscious by the initial detonation or were drowned when the conning tower flooded.

10-30. It is of course obvious that had the tactical situation permitted TANG to remain in the position she assumed immediately after being torpedoed, the escape problem would have been enormously simplified. With the stern on the bottom in 180 feet of water and with the bow about 25 feet out of water, the forward escape trunk door was only 24 feet below the surface. At this shallow depth it is entirely feasible to make a "free" escape without the aid of a "lung" and without having to vent excess air through the open mouth as is mandatory when escaping from greater depths. All that is required is that the escaping man exhale slightly just prior to leaving the trunk and he can then hold his breath the rest of the way if he so prefers. However, even relatively simple escape problems become difficult when personnel have been rendered physically and mentally debilitated by long exposure to poor atmosphere. The case of HMS THETIS is an outstanding example. THETIS sank in a depth of 120 feet while on trials off Liverpool in June 1939 as a result of opening a torpedo tube breech door with the muzzle door also open. After seventeen hours the crew lightened the submarine aft sufficiently to get the stern out of water. In this position the after escape chamber was only about ten feet below the surface. By that time most of the crew had headaches and breathing was becoming increasingly difficult due to the high CO2 content of the atmosphere. The extreme angle of the boat plus the deteriorated physical condition of the crew made movements to the after escape station very trying. Two officers successfully escaped at this time but when the chamber was drained down, water reached the main motor control equipment and started an electrical fire which further depreciated breathing conditions by adding large quantities of smoke to the atmosphere. Only two more men made an escape. The remainder were apparently physically and mentally incapable of making the escape effort even though at this time the escape chamber was still but slightly below the surface.

10-31. TANG's loss illustrates the following points:

(a) A surfaced submarine in maximum diving trim which sustains pressure hull damage of sufficient magnitude to cause immediate flooding of two or more adjacent end compartments will probably up-end

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so rapidly that the crew will in all likelihood not be able to abandon ship prior to sinking. 1,2

(b) In the event of (a), if damage control measures are promptly executed it is probable that watertight integrity can be established at one of the escape stations plus several intermediate compartments as the boat sinks.2

(c) Assuming the boat then hits bottom in a depth suitable for escape operations, some or all of those men who manage to make their way to an escape position should, by properly carrying out the escape procedure, be able to reach the surface either with the aid of "lungs" and an ascending line or by "free" escapes.2 TANG represents the only known case n the history of the U.S. Navy of individual underwater escapes from a disabled submarine in either war or peace.

(d) Wartime training methods were apparently not sufficiently rigorous to install adequate confidence in, and knowledge of, the escape procedure.


1 On her fourth war patrol, BESUGO (SS321) secured one torpedo hit on a surfaced German submarine, U-183 (740 tons). The U-boat sank in 2 to 4 seconds. There was only one survivor and he was carried far underwater.
2 While operating under ComSubsSoWesPac on her fourth war patrol, the Dutch submarine HNMS ZWAARDVISCH secured one torpedo hit in the forward torpedo room of a surfaced German supply submarine (1600 tons). The German boat is reported to have sunk in about 30 seconds. Twenty-one men escaped after the submarine reached bottom in 120 feet of water. The majority of these men made "free" escapes from the control room while only a few used breathing equipment.

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Photo 10-1: TANG (SS306). View showing torpedoing of U-977 by ATULE (SS403) on 13 November 1946. Note that the pressure hull of U-977 has apparently been completely severed by the detonation and that the forward and after portions of the hull have jack-knifed. U-977 was a standard German Type VII-C design: length 220' -2"; maximum beam 20'-4"; diameter of pressure hull 15'-5"; pressure hull plating thickness .73"; and submerged displacement 880 tons. TANG's pressure hull was 16'-0" in diameter with .87" HTS plating, and was therefore of slightly greater strength than that of U-977. The torpedo used by ATULE was a Mark 14 body fitted with a Mark 16, Mod. 4 magnetic proximity-fuzed warhead containing 660 lbs. of Torpex, and is believed to have detonated almost directly underneath the keel of U-977. The charge which sank TANG was 570 pounds of Torpex, or only slightly less than that employed against U-977. This photograph demonstrates the great destructive power of torpedoes when used against unprotected ships such as submarines. The upward movement of the hull shown here would not have been nearly as pronounced in the case of TANG, however, since her displacement was almost three times that of U-977, the torpedo struck TANG aft rather than amidships, and was a contact side detonation rather than a non-contact under-the-bottom detonation.

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Photo 10-2: TANG (SS306). Photo taken on 2 December 1943.

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Plate X: Torpedo Damage.


SECTION XI

U.S.S. BERGALL (SS320)

Mine Damage

Gulf of Siam

13 June 1945

Class

SS285

Builder

Electric Boat Co., Groton, Conn.

Commissioned

12 June 1944

Length (Overall)

311 ft. 9 in.

Beam (Extreme)

27 ft. 3 in.

Submergence Depth (Designed Maximum)(Axis)

400 ft.

Displacements

Standard

1525 tons

Emergency Diving Trim

2050 tons

Submerged

2415 tons

Draft (Mean, Emergency Diving Trim)

16 ft. 10 in.

Type of Propulsion

Diesel Electric Reduction Drive

Main Engines (4)

General Motors 16-278A

Main Motors (4) and Generators (4)

GEneral Electric Co.

Reference:

(a) C.O. BERGALL conf. ltr. SS320/A16-3/A9, Serial No. 0267 of 17 June 1945 (Report of War Patrol Number Five).

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11-1. While conducting a surface search for a Japanese convoy in the Gulf of Siam on the night of 13 June 1945, during her fifth war patrol, BERGALL sustained damage to propulsion machinery as the result of an underwater detonation which occurred close aboard on her port quarter. The detonation is believed to have been caused by actuation of a proximity-fuzed mine. Propulsion power was temporarily lost and both reduction gears were damaged, although not seriously enough to render the machinery plant inoperative. As a result of the ensuing high noise level in both reduction gears, BERGALL was forced to terminate her patrol. This case is primarily of interest in that it is one of the few war damage experiences which illustrates the effect of a close underwater detonation on the Diesel propulsion plant of a U.S. submarine while running surfaced.1 In addition, it is one of the many cases which demonstrates the susceptibility of reduction gears to damage. This report is based on the information contained in the reference.

11-2. After a two-week refit by the U.S. Navy Submarine Repair Unit No. 137, BERGALL departed Freemantle, West Australia, on 12 May 1945 for her fifth war patrol. On 21 May she arrived on station in her assigned area in the waters of the Gulf of Siam. Although BERGALL covered her area thoroughly, only two contacts worthy of attack were made. The first was on 30 May when two Japanese tugs and five barges were sunk by the combined use of 20mm, 40mm and 5-inch/25 cal. gunfire at a range of about 600 yards.

11-3. The second contact was made during daylight on 12 June when a slow convoy of two small tankers and one small cargo ship, escorted by one surface vessel and one aircraft, was sighted close inshore and proceeding north. BERGALL commenced a submerged approach but range could not be closed to less than 5000 yards due to the shallow waters in which the enemy ships were operating. It was therefore decided to refrain from attacking at that time but to attempt to regain contact with the convoy after dark for a possible night surface attack.

11-4. BERGALL surfaced at 2010 that night and headed north, searching for the enemy convoy along the coast and in likely anchorage areas. Contact had not yet been regained, however, when at 0110 on 13 June, while investigating the bight in the Gulf of Siam near Kaw Luem, lat. 11° 45'N., long. 90° 50'E., a heavy detonation occurred close aboard BERGALL's port side abreast the maneuvering room. At this moment, BERGALL had just completed her search of the bay and was reversing course with left full rudder. The ship was making about 13 or 14 knots with two engines on propulsion, the shore line was less than two miles distant and the water depth was but 42 feet.

11-5. It is quite likely that the detonation was caused by a proximity-fuzed mine, inadvertently actuated by BERGALL, for this particular area had been previously mined by U.S. and British aircraft operating from bases in Asia. A subsequent check of BERGALL's track disclosed that she had run three miles inside the limits of the minefield. Seventh Fleet Submarines had not at this time been notified of the presence of Allied mines in this area. The field contained both acoustic and magnetic-


1 One other such case is that of FLYING FISH (SS229) on 24 May 1944 as the result of a premature detonation of one of her own torpedoes. See brief in Appendix I.

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induction ground mines of various types, with explosive charges ranging from 490 pounds to 700 pounds TPX.1

11-6. The impact of the detonation jarred the entire ship. Personnel were knocked off their feet, tossed out of bunks, and in the maneuvering room were thrown up against the overhead. Lighting failed in the maneuvering and after torpedo rooms. The overspeed trips operated on Nos. 2 and 3 main Diesel engines, which were on propulsion, and No. main Diesel engine, which was charging the batteries, causing all three engines to stop and thereby cutting off power to the main propulsion motors. The loss of load on Nos. 1, 2 and 3 generators and the jarring of the contactors for these generators in the main control cubicle caused severe arcing across the contactor tips and ignition of the leads. Severe arcing also occurred across the closed motor bus tie contactor tips in the control cubicle. Inspection disclosed that these contactor surfaces were extensively burned. The No. 4 generator reverse current relay was found to have been rendered inoperative.

11-7. Propulsion was quickly shifted to the forward and after batteries enabling the ship to get underway again within a few minutes after the detonation. Loud knocking was heard in the port reduction gear and to a lesser extent in the starboard gear. The port shaft was secured immediately to prevent possible additional damage to the port reduction gear and BERGALL proceeded to clear the area on the starboard shaft only. No enemy interference was encountered.

11-8. As stated above, when the detonation occurred, BERGALL was reversing course with full left rudder. The steering system was in power operation. Electrical power to the steering motor was lost at once due to fuzes in the motor control panel jarring out of their holders. This occurred in spite of the fact that these holders were of the improved high impact design. The casing on the lower after bearing of the port tiller ram was torn loose although the bearing itself appeared undamaged. The rudder jammed hard against its stops but after shifting to hand operation at the change valve in the control room, steering control was regained in time to steady on the desired escape course. No difficulty was experienced with the rudder in hand operation. The rudder angle indicator transmitter worm wheel was jarred out of mesh with its rack on the tiller ram and remained out of commission until repaired several hours later. In the intervening period, rudder angles were determined by the after torpedo room rudder angle indicator and relayed to the control room and bridge by sound powered telephone.


1 The records of this minefield indicate that it contained a total of 6 acoustic and 28 magnetic-induction type mines. All were aircraft laid ground mines. Types and numbers of these mines were as follows:

6 - U.S. Mk. 13, Mod. 5 (Acoustic, 490 pounds TPX)
6 - U.S. Mk. 26, Mod. 1 (Magnetic, 525 pounds TPX)
3 - U.S. Mk. 36, Mod. 1 (Magnetic, 635 pounds TPX)
2 - U.S. Mk. 13, Mod. 0 (Magnetic, 700 pounds TPX)
2 - British A-Mk. V (Magnetic, 675 pounds Minol) 15 - British A-Mk. VII (Magnetic, 620 pounds Minol)

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11-9. Chlorine gas was reported in the forward battery compartment immediately after the detonation and this space was promptly sealed. It was found, however, that a vinegar jug in the galley had broken and the erroneous chlorine gas report originated when the vinegar fumes were carried through the supply ventilation system to the forward battery room. The compartment was therefore opened up again.

11-10. By 0130, twenty minutes after the damage occurred, two main Diesels had been started again and put on propulsion. Both batteries were secured. Normal power operation of the steering system had been regained. BERGALL headed for the mouth of the Gulf of Siam, still using the starboard shaft only. At 0445 power was put on both shafts and speed was increased to 14 knots. The port reduction gear was very noisy at this speed but the vibration was not considered dangerous.

11-11. At 0705 BERGALL submerged, stopped the port shaft and opened the port reduction gear inspection plate. No tooth damage was apparent but the after end of the port gear casing was found to have shifted 3/16 of an inch outboard on the bedplates, the studs apparently having either been bent or sheared.

11-12. Since the noise level of the reduction gears was too high to permit submerged approach on escorted ships, and the lack of contacts to date in that area indicated little likelihood that an opportunity might present itself for a night surface attack during the few days remaining of her scheduled on-station period, BERGALL terminated the patrol and proceeded to Subic Bay, P. I., for further inspection and repairs.

11-13. With the exception of one sheared holding-down bolt outboard and aft on No. 4 main engine, and the operation under impact of the overspeed trips for Nos. 1, 2 and 3 main engines, no damage occurred to the Diesel engines proper and they performed satisfactorily until the next Navy Yard routine overhaul. The bushing on the engine air starting lever twisted loose, however, resulting in considerable loss of air (500-pound) from the air starting flasks. There was no other reported damage to equipment or systems in either of the two engine rooms. No damage occurred forward of the engine rooms with the one exception of bent slip rings on the SJ radar antenna.

11-14. In the maneuvering room, no damage occurred to the main control cubicle other than that mentioned in paragraph 11-6 above. Various minor derangements were found in this space, however, such as sheared studs, fractured welds on brackets, displacement of sheet metal bulkheads, etc.

11-15. In the motor room, a considerable leak developed around the port stern tube packing. Adapters on the lubricating oil lines were cracked at the forward bearings for main motors Nos. 1, 2 and 3 and at the after bearing of main motor No. 4. The bearing caps on Nos. 3 and 4 main motor bearings were found to have been loosened.

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11-16. The dog operating mechanism of the upper hatch for the after torpedo room access trunk spun open and it is interesting to note that the holding turnbuckles, which had been installed during the previous refit, were all that prevented this hatch from opening.

11-17. Considerable damage occurred to the operating gear of the after torpedo tubes. The emergency poppet valve, for tube No. 9 jammed in the open position. The torpedo tube blow and vent manifold was jarred loose and the studs holding the vent-closing valves of the poppet system for tubes Nos. 7, 8 and 9 to the underside of the blow and vent manifold were sheared. The stop bolt rods on the four after torpedo tubes were distorted, resulting in minor leakage into the boat through the packing glands at the after trim tank bulkhead. Later inspection disclosed that three of the four after torpedo tubes were distorted to the extent that the torpedoes within had to be removed by chainfall and reloads could not be made. Both the hydrogen burning panel and the Mk. 18 torpedo charging panels were torn loose from their mountings. The track locking mechanism on one torpedo handling skid was broken. One Mk. 27 torpedo was thrown up from its stowage rack and struck the bunk above, causing a slight dent in the case of the TPX-loaded warhead.

11-18. BERGALL arrived at Subic Bay on 17 June 1945. Since investigation of the damages indicated that complete repairs were beyond the capacity of local forces, the ship was ordered to the Navy Yard, Portsmouth, N. H., where she arrived on 5 August. There complete war damage repairs together with routine overhaul and outstanding alterations were accomplished, the major item of work being repairs to the main reduction gears. Both of these gears were removed from the ship for complete inspection. On the port reduction gear, the noisiest one, it was found that the outboard pinion had been driven into the bull gear by the shock of the mine detonation. The gear assembly was considered mechanically satisfactory for it had been used during the entire 10,000-mile run to the U.S. east coast from the Philippines. However, although all points of observable impact were stoned, the high noise level in this gear could not be reduced to meet satisfactory operational requirements. It was then sent to the manufacturer for reconditioning and a new port reduction gear assembly was installed in the ship. The starboard reduction gear was found to be only slightly damaged and was returned to the ship after repairs by the Navy Yard. All work was completed and BERGALL was returned to service on 19 November 1945, about five months after the initial damage was incurred.

11-19. That BERGALL did not sustain more severe damage from the detonation was due to the fact that the mine was actuated while still at an estimated distance of between 90 and 120 feet from the hull, well outside the serious damaging-range of the mines known to have been in this field. Since both acoustic and magnetic proximity-fuzed mines are known to have been present in BERGALL's vicinity, it is not possible to determine which type of mine caused the damage.

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11-20. The sensitivities of such proximity-fuzed mines are normally set for the average acoustic or magnetic characteristics of the vessels they are intended to act against so that detonation will occur when within a range calculated to cause severe or lethal damage. It is entirely possible for such mines to be swept at relatively harmless distances when the actuating influence is considerably greater than expected. For example, in the case of acoustic mines of the sonic frequency type, such as those in this field, the frequency and intensity of sound generated by submarine Diesel propulsion plants is understood to be capable of causing detonation at a considerably greater range than surface ship steam propulsion plants.

11-21. The magnetic-induction type influence mine is fuzed to detonate when the rate of change in the surrounding magnetic field exceeds a predetermined amount. This rate of change is proportional to the velocity of the ship with respect to the mine and, for a given relative velocity, will be greatest when the ship is turning through a north or south magnetic heading. Since BERGALL was reversing course at about 14 knots when the mine detonated, it is probable that her magnetic "influence" was at or near the maximum possible for that speed. It is understood that many U.S. magnetic ground mines are fuzed so sensitively that steel hulled minesweepers are not considered safe when passing overhead in less than 120 feet of water. It is not unusual for magnetic mines to detonate at distances of over 100 feet. BERGALL was ranged at Freemantle, Australia, in November 1944, at which time it was found that her signature was similar to that of an untreated and undegaussed submarine. The ship was again ranged at Pearl Harbor in July 1945, while en route to the United States shortly after the damage occurred, and her signature at this time was reported as being satisfactory for the Pearl Harbor area. Due to variation in the earth's magnetic field with latitude, however, this signature would have been 4 or 5 times greater than that of a degaussed submarine for the magnetic conditions existing in the Gulf of Siam where the mine was detonated. This would of course have greatly increased the likelihood of remote operation of a magnetic-induction type mine.

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SECTION XII

U.S.S. GRAMPUS (SS207)

Gunfire Damage

Off Truk

17 May 1942

Class

SS198

Builder

Electric Boat Co., Groton, Conn.

Commissioned

23 May 1941

Length (Overall)

307 ft. 2 in.

Beam (Extreme)

27 ft 3 in.

Submergence Depth (Designed Maximum)(Axis)

250 ft.

Displacements

Standard

1475 tons

Emergency Diving Trim

1990 tons

Submerged

2359 tons

Draft (Mean, Emergency Diving Trim)

16 ft. 9 in.

Type of Propulsion

Diesel Electric Reduction Drive

Main Engines (4)

General Motors 16-248

Main Motors (4) and Generators (4)

References:

(a) C.O. GRAMPUS conf. ltr. A16-3/SS207, Serial No. 04 of 17 June 1942 (Report of War Patrol Number Two).
(b) C.O. GRAMPUS conf. ltr. L11-1/SS207, Serial No. 05 of 30 June 1942 (Report of War Damage).

Photographs Nos. 12-1 through 12-3 (furnished by CO. GRAMPUS).

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12-1. On the night of 17 May 1942, while conducting a surface patrol off Truk during her second war patrol, GRAMPUS was detected by a Japanese patrol vessel and forced to make a quick dive. While passing 30 foot depth, one shell, believed to have been a 3-inch or 4.7-inch common projectile, struck the starboard bulwark of the cigarette deck and detonated approximately three feet beyond its point of impact about two feet above the cigarette deck over the main engine air induction trunk. While no damage of a serious or military nature was caused, and GRAMPUS experienced no difficulty in subsequently evading the enemy, the action has been included in this report to illustrate the shrapnel effect of medium caliber projectiles and the obvious vulnerability of submarines to such attacks. While other U. S. submarines have been more heavily damaged by gunfire attack, this experience of GRAMPUS was chosen since it is the only such action in which photographs of the damage were available to the Bureau.

12-2. The damage report, reference (b), submitted by the Commanding Officer while the ship was undergoing repairs by OTUS (Ex-AS20) at Fremantle, W.A., is clear and comprehensive, and is therefore reproduced below in lieu of the usual narrative.

Fleet Post Office
San Francisco, California
30 June 1942

From:

The Commanding Officer

To:

The Chief of the Bureau of Ships

Subject:

War Damage Inflicted upon U.S.S. GRAMPUS, Report of.

Reference:

(a) BuShips ltr. C-FS/L11-1(374); C-EN28/A2-11 of April 17 1942.

Enclosure:

(A) Photographs of subject damage.

1. At 1906 (ZT) on May 17, 1942, the U.S.S. GRAMPUS surfaced on course 270° T., about twenty miles North West of the North pass to Truk Island in approximate Latitude 08° -02'-00" North and Longitude 151° -30,-00" East. This vessel had been conducting submerged patrol in assigned area. There was a moderate sea from the North East with a surface wind of about eight knots, estimated visibility 4,000 yards. At 1910 sighted a light astern that appeared to be a flash of a searchlight. At 1912 changed course to 340° T., and headed away. At 1917 echo ranging was heard on bearing 270° relative. Nothing sighted upon careful observation. At 1927 changed course to 000° T., and went to standard speed on two engines. At 1941 slowed to listen with sound gear. At 1947 simultaneously sighted and picked up with sound a vessel approximately 1500 yards on the starboard beam identified as a Japanese patrol vessel of about 500 tons. Immediately thereafter, the patrol vessel illuminated with its searchlight. The bridge was cleared and a quick dive was made to escape. At

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1949 while at 30 foot depth, a sharp crack was felt in the vicinity of the bridge. The ship was checked quickly for leaks but no flooding was detected. The ship was ordered to run silently at deep submergence. At 1952 upon reaching 100 foot depth, the explosions of three depth charges were felt which were evidently close by. Between 2001 and 2005 eight depth charges were felt and screws and echo ranging heard on sound gear from three different sources. At 2044 one explosion was heard at a long range. Shortly afterwards lost contact with enemy. At 2125 surfaced on course 320° T.

2. A survey of the ship revealed that the following damage had been sustained: (1) Large shell hole approximately 4 feet in diameter in the starboard bulkhead of the cigarette deck. (2) Wooden gratings on cigarette deck splintered. (3) Cigarette deck above engine induction dished in and riddled with shrapnel holes. (4) .50 caliber machine gun mount blown off its foundation and a number of shrapnel holes in the mount. (5) Shrapnel hole about 1/2" in diameter in R.D.F. antenna loop shafting. (6) Port bulkhead and bridge structure including shelter space riddled with shrapnel leaving holes in plating varying from 3 inches in diameter to 1/4" in diameter. (7) Both after radio antennae carried away. None of the damage suffered was of a serious or military nature.

3. The best estimate of the size of the projectile used was of about 4.7" in diameter. It was evidently a high explosive shell with an instantaneous fuze. The shell pierced the bulkhead and exploded approximately three feet beyond its point of impact just above the engine induction. The fragmentation was small with a wide dispersion. The heaviest plating penetrated by the projectile and the shrapnel was 5 pound galvanized iron plate.

4. The damage was repaired by the repair force of the U.S.S. OTUS at Fremantle, W.A.

E. S. HUTCHINSON
Copies to:
COMINCH
BUORD

12-3. The damage to GRAMPUS as the result of this attack was superficial (Photos 12-1, 12-2 and 12-3) and she remained on patrol in the TRUK area until 5 June, when she departed for Fremantle, W.A., arriving on 17 June. The nature of the damage indicates that a 3 or 4.7-inch common projectile was employed. The larger Japanese anti-submarine vessels, such as frigates and large gunboats, usually were provided with one or more 12 cm./45 caliber guns(4.7-inch) with common projectiles having bursting charges ranging from 4 to 7 pounds of TNT or picric acid. Smaller anti-submarine vessels, such as the PC-13 Class, usually mounted one 8 cm./40 caliber gun (3-inch) with common projectiles having bursting charges ranging from 1 to 1.5 pounds of TNT or picric acid. Special flat-nosed anti-ricochet projectiles were frequently used by the Japanese for anti-submarine work.

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12-4. Had the projectile struck a foot or so lower, or had GRAMPUS been a second or two slower in diving, serious damage would have resulted.

12-5. For other cases of gunfire damage to U.S. submarines, attention of the reader is invited to the following briefs of damage in Appendix I: SWORDFISH (SS193), 7 February 1943; SKATE (SS305), 6 October 1943; NAUTILUS (SS168), 19 November 1943: BOWFIN (SS287), 28 November 1943; ROCK (SS274). 29 February 1944; RONQUIL (SS396), 17 November 1944: BERGALL (SS320), 13 December 1944; POGY (SS266) 19 April 1945; MUSKALLUNGE (SS262), 8 August 1945.

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Photo 12-1: GRAMPUS (SS207). Projectile entry hole in starboard bulwark of cigarette deck.

Photo 12-2: GRAMPUS (SS207). View showing fragmentation damage. Projectile is believed to have detonated approximately over the outboard engine air induction valve about two feet above the cigarette deck.

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Photo 12-3: GRAMPUS (SS207). Fragmentation damage, port bulwark forward end of cigarette deck.

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SECTION XIII

U.S.S. GROWLER (SS215)

Collision and Machine Gun Strafing Damage

Off New Britain, Bismarck Archipelago

7 February 1943

Class

SS212

Builder

Electric Boat Co., Groton, Conn.

Commissioned

20 March 1942

Length (Overall)

311 ft. 9 in.

Beam (Extreme)

27 ft. 3-3/4 in.

Submergence Depth (Designed Maximum)(Axis)

300 ft.

Displacements

Standard

1525 tons

Emergency Diving Trim

2050 tons

Submerged

2415 tons

Draft (Mean, Emergency Diving Trim)

16 ft. 10 in.

Type of Propulsion

Diesel Electric Reduction Drive

Main Engines (4)

General Motors Model 16-248

Main Motors (4) and Generators (4)

General Electric Co.

References:

(a) C.O. GROWLER conf. ltr. C-SS215/A16-3, Serial No. 0153 of 17 February 1943 (Report of War Patrol Number Four).
(b) CTF 42 conf. ltr. FF12-15(42)/A16-3/00-jm, Serial No. 057 of 18 February 1943 (Comments on CO. GROWLER Report of War Patrol Number Four).
(c) ComSubRon Eight Conf. ltr. FC5-8/S11/L11, Serial No. 054 of 25 May 1943 (Repairs to GROWLER Battle Damage).

Photographs Nos. 13-1 through 13-8 (furnished by Commander Submarine Squadron Eight).

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13-1. On 7 February 1943, while on her fourth war patrol, GROWLER underwent the unique experience of ramming and possibly sinking a large enemy patrol frigate. Damage to GROWLER due to the collision and subsequent close quarter enemy machine gun fire was not sufficiently serious to prevent her from making a submerged escape and returning to base in a seaworthy condition. This report is based on the information contained in the references and on interviews with various officers attached to GROWLER. The Photographs were furnished by Commander Submarine Squadron Eight.

13-2. GROWLER arrived at Brisbane, Australia, on 10 December 1942 from her third war patrol. Normal refit was undertaken by FULTON (AS11) and completed on 31 December. On 1 January 1943 GROWLER departed Brisbane for her fourth war patrol and on 11 January reached her assigned patrol area in the waters adjacent to New Britain and New Ireland Islands in the Bismarck Archipelago.

13-3. Although many contacts were made with enemy shipping during her first few days on station, GROWLER was able to close to attack position only once. This occurred on 16 January when she sank a medium-sized freighter northwest of Watom Island with two torpedo hits during a daylight periscope attack. On 20 January GROWLER shifted her patrol area to cover the western approaches to Rabaul and on 30 January damaged a medium-sized freighter near Mussau Island by one torpedo hit during a night surface attack.

13-4. On 2 February GROWLER started patrolling toward Rabaul. On the night of 4-5 February, when south of Steffen Strait, radar contact was established with an enemy convoy and GROWLER commenced a surface chase. However, with range closed to about 5000 yards, she was detected, subjected to medium caliber gun fire and forced to submerge. Shortly afterwards, two fairly close depth charge attacks of four charges each were delivered by one of the convoy's escorts, the second of which partially blew oat the gasket to the No. 1 MBT boiler type manhole cover in the deck of the forward torpedo room.

13-5. Water entered in considerable volume through this opening but not in sufficient quantity to seriously affect depth control and GROWLER managed to lose the enemy escorts about one-half hour later. The leak grew steadily worse, however, and by one hour after the initial attack, water was entering the forward torpedo room at an estimated rate of over 1000 gallons per hour. The drain pump was run continuously on the torpedo room bilges and this sufficed to keep the water level within the compartment under control. An effort was also made to close off the manhole by using a sheet rubber gasket backed by deck plates held in place by shores and two jacks. This measure did not stop the leak but was reported to have prevented it from becoming more serious. Surfacing during daylight hours for repairs was not considered feasible due to the close proximity of the searching enemy anti-submarine vessels and, although diving trim control was poor, GROWLER remained submerged. Upon surfacing after dark, repairs were quickly effected by placing the forward

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torpedo room under 7 pounds per square inch air pressure and renewing the manhole gasket. A test dive was then made and the new gasket was found to be satisfactory.1

13-6. During 5-6 February GROWLER remained on submerged patrol off Watom Island. At 2200 6 February orders were received to shift station and GROWLER proceeded to her new area on the surface at 17 knots. At 0110 7 February, while in a position about 50 miles off the northwestern end of New Britain Island, lat. 3° 34'S., long. 151° 09'E., GROWLER established contact with a large Japanese converted patrol frigate. Visibility was poor and limited to about 2000 yards. The enemy ship was just barely discernible off the starboard bow and was proceeding on opposite course. GROWLER immediately turned away, made her tubes ready and then headed directly toward the frigate for a surface torpedo attack.

13-7. When GROWLER was almost in firing position, with radar range of 2000 yards and track angle 130° starboard to the target, the enemy frigate sighted her, immediately reversed course and closed to make a counterattack. This maneuver was apparently not immediately discerned by the bridge on GROWLER although the fire control party in the conning tower is reported to have given accurate radar ranges and to have had the TDC solution. At 0134, after range to the enemy vessel as indicated by TDC track and radar was too close to permit torpedo fire, the bridge gave the order "Left full rudder" and sounded the collision alarm. At 0135, while swinging with left rudder and at speed 17 knots, GROWLER rammed the enemy frigate head on, striking midway between her bow and bridge.

13-8. The impact of collision was terrific, heeling GROWLER to about 50 degrees and knocking most of the crew off their feet. Immediately afterwards, the enemy opened fire on GROWLER's bridge with one or more 13mm machine guns2 at point blank range and on GROWLER the order was given "Clear the bridge". Four of the seven men present on the bridge descended into the conning tower. Two of these men were wounded and had to be helped through the upper hatch. After approximately 30 seconds had elapsed since the last man had come below and still no one else had appeared at the hatch, the diving alarm was sounded, upper conning tower hatch was secured and GROWLER submerged. The enemy continued strafing the bridge with machine gun fire until it was under water. It is believed that the three men remaining topside, the Commanding Officer, the assistant Officer of the Deck and a lookout, were killed or seriously wounded by the enemy fire before GROWLER submerged and for that reason were unable to clear the bridge.


1 As a result of GROWLER's experience and reports of similar casualties from other submarines, the Bureau authorized by ShipAlt SS167 of 12 March 1943 the replacement with welded blanks of the forward and after ballast tank boiler type manhole covers as installed in the torpedo room decks on SS175-284. On SS285 and subsequent submarines, such ballast tank accesses were omitted from the design.
2 Recovered projectiles were measured and found to be 13mm.

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13-9. Damage to GROWLER can be conveniently divided into two categories: (a) damage due to the collision and (b) damage due either directly or indirectly to the enemy machine gun fire. Damage due to collision was limited to the extreme forward portion of the ship. The entire bow structure forward of frame 10, a length of about 25 feet, was either crumpled or considerably distorted and forward of frame 4 was bent about 90 degrees to port (Photos 13-1 and 13-2). This structure consists only of the relatively light plating and framing of the bow buoyancy tank (10-pound MS). Deck plating back to frame 12 was wrinkled and torn. Bulkhead No. 10 was dished in only about 3/4 inch at the centerline in way of the torpedo tube nest but above the tubes was distorted somewhat more extensively (Photo 13-3). Grease lines, bow buoyancy tank vent valves and operating gear, and the torpedo tube shutters and operating gear were completely wrecked. On subsequent docking, it was found that No. 3 torpedo tube shutter had jammed into No. 3 tube outer door gasket groove but that no damage had occurred to any of the forward torpedo tubes proper. The bow planes operated without difficulty and were undamaged with the exception of slight misalignment of the tilting shaft. Depth control was reported as being somewhat difficult after the collision and during the return trip to base. This is attributable to the protruding structure of the damaged bow (Photos 13-1 and 13-2) which acted as both a fixed plane and "plow" at maximum lever-arm distance from the turning center of the boat and also blanked off normal flow of water to the port bow plane, thereby considerably altering its planing effect.

13-10. Direct materiel damage due to the enemy machine gun fire was in itself relatively minor but the indirect damage caused by resultant flooding became quite serious. Although the bridge and conning tower fairwater were hit in numerous places1 (Photo 13-4), fortunately only one projectile pierced the pressure hull. This penetrated the bronze upper conning tower hatch while it was in the open position prior to diving and tore a hole about 1/2 inch wide and 3/4 inch long (Photo 13-5). Two other projectiles struck the No. 1 periscope shear pipe structure in the bridge "covered wagon", jamming the periscope so that it could neither be trained, raised or lowered but caused no damage to the periscope tube itself (Photo 13-6). Electrical cables on the bridge for the collision alarm, IMG, sidelights, target bearing transmitters and bridge steering repeaters were shot away. On submerging, water entered the conning tower in large volume through the sheathing of these punctured cables2 in addition to the hatch bullet hole. Although the leaks were observed as soon as GROWLER's conning tower went under, no attempt was made to surface due to the presence of the enemy vessel above nor was the conning tower abandoned. Efforts were made to plug the leaks but were largely unsuccessful. Depth was maintained at 150 feet in spite of the flooding and the subsequent detonations of two depth charges which were not close and did no damage.


1 The conning tower fairwater and bridge plating on GROWLER were but 5-pound and 7-1/2 pound weight MS. As a result of this and other actions, the installation of 25-pound and 30-pound STS plating for the protection of bridge personnel was authorized by ShipAlt SS177 of 16 April 1943 for all fleet type submarines subsequent to SS197.
2 For further discussion of cable sheathing leaks, see paragraph 19-12.

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13-11. Water overflowed from the conning tower bilges to the control room deck, where it reached a depth of about 6 inches, and further drained to the pump room bilges where it accumulated to a depth of several feet. Both the trim and drain pumps were continuously operated in an effort to control the flooding. Most of the electrical circuits in the conning tower, control room and pump room grounded out or received minor damage from salt water spray or direct flooding. All gyro, I.C., lighting and heater circuits, and the majority of the electrical panels in these spaces were completely disabled. The ST radar range indicator unit in the conning tower was flooded out. In the pump room many auxiliaries were grounded and, as a result of these short-circuits, a small fire broke out in the No. 2 auxiliary power panel aft in the maneuvering room. This was promptly smothered by CO2 fire extinguishers and all circuits were temporarily pulled with the exception of the field circuits for the main generators. Several small hydraulic and air piping and fitting leaks developed in various places as a result of the collision impact, but these were not serious and were either tightened up, isolated, or left as is.

13-12. At 0145, the JK-QC sound gear, which had been temporarily deranged (reason not reported), was placed back in commission. However, no contact could be established with the Japanese patrol vessel. Since the light hull of the enemy ship must have been opened to the sea over a considerable area as a result of being rammed by GROWLER, it is quite possible that she might either have sunk or become completely immobilized by this time due to progressive flooding.1

13-13. At 0201, after approximately one-half hour of submerged running since the collision had occurred, and still not having obtained any sound contacts with the enemy vessel, a battle surface was made. No ships were in sight so GROWLER cleared the area by a surface run to the westward. Topside and internal damage was then surveyed and emergency repairs made where possible. The conning tower hatch leak was plugged with a bolt and lead washers. At dawn the ship submerged once more and remained down until evening. Leaks in the conning tower were still very bad but were under control. A canvas chute was rigged from the conning tower lower hatch through the control room hatch to the pump room bilges and this proved adequate to prevent further water damage. At 1848 GROWLER again surfaced, continued with repair work, and sent a report to Commander Task Force 42 stating that a return to base was being made via the designated emergency routing. During this period the No. 2 periscope, No. 1 high pressure air compressor, No. 1 low pressure air compressor, and refrigeration and air conditioning units were placed in operating condition and grounds cleared. All remaining leaks were effectively stopped. Diving control was reported as still being somewhat difficult.


1 Japanese records obtained upon the termination of World War II contain no mention of any anti-submarine attack or the sinking of any Japanese ship which could conceivably have corresponded to this action of GROWLER. Japanese records were notoriously inaccurate and incomplete, however, and it is entirely possible that the enemy patrol vessel may have been sunk and yet never reported as sunk or even overdue to any central Japanese agency.

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13-14. GROWLER made the return trip back to base by running submerged during daylight hours while in enemy patrolled waters and running surfaced at night. She arrived alongside FULTON (ASH) at Brisbane, Australia, on 17 February 1943.

13-15. After a survey of the damage it was considered both possible and desirable to undertake complete repairs with local facilities, provided damage to the forward torpedo tubes was not extensive. A drydock examination disclosed that the tubes were undamaged and in correct alignment, with the exception of the previously mentioned damage to muzzle door operating gear and shutters. The Evans Deakin Company of Brisbane undertook replacement of the damaged bow structure, prefabricating and installing the new bow in two horizontal sections (Photo 13-7). Fittings were salvaged from the damaged structure where possible. The work was accomplished in the Moreton graving dock, Brisbane. FULTON undertook all other battle damage repairs and in addition gave the ship a regular refit. All work was completed and GROWLER was returned to service on 4 May 1943.

13-16. GROWLER's experience illustrates that, should the tactical situation so require, it is possible for modern fleet type submarines to successfully ram light-hulled vessels such as destroyers or patrol craft without necessarily destroying their own watertight integrity, seaworthiness and ability to conduct submerged operations.1 This is principally attributable to the 30 odd feet of non-watertight bow structure ahead of the forwardmost pressure hull bulkheads, in this case the forward and after bulkheads of the forward trim tank. This bow structure effectively cushions collision shock by absorbing the damage in a non-vital area while depleting the relative momentum of the two ships involved, and tends to prevent serious injury to pressure hull structure farther aft.

13-17. GROWLER's experience also demonstrates the extreme vulnerability of unarmored submarines, when surfaced, to even small caliber projectiles, as from aircraft strafing or light machine gun fire from surface vessels. It was fortunate for GROWLER that the enemy machine gun fire was directed at her bridge instead of her pressure hull or conning tower. Had the latter been the case, the resulting numerous small holes might have prevented GROWLER from


1 Another excellent example is the collision between ARGONAUT (SS475) and HONOLULU (CL48) on 8 January 1946 off the U.S. east coast. The angle of collision was about 30 degrees, ARGONAUT's bow striking about 75 feet aft of the stem on HONOLULU'S starboard bow. Although both ships started backing down just prior to the collision, the relative speed of the two ships at the instant of initial contact is believed to have been in excess of 20 knots. Damage to ARGONAUT was very similar to but more severe than that which occurred to GROWLER. The bow forward of frame 11 was completely crumpled and bent 90 degrees to starboard. Minor damage was sustained to plating, framing and the vertical keel between frames 11 and 16 (MBT No. 1) but no damage occurred to the forwardmost pressure bulkhead at frame 16. The outboard and intermediate sections of all forward torpedo tubes were bent to starboard. No internal flooding whatever occurred on ARGONAUT and she remained seaworthy and could have submerged had the occasion required.

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making a submerged escape after the ramming and in that case the enemy frigate very probably would have completed her destruction. Even presuming GROWLER were to escape the enemy ship on the surface, multiple small holes in the pressure hull and external tanks might still have caused her loss, either by direct flooding or by preventing submergence if again attacked while making the surface run back to base through enemy controlled waters. Ballistic data shows that U.S. 50 caliber AP (M2) and Japanese 13mm AP projectiles, when fired from within 500 yards range at 0° obliquity, will penetrate both the outer and inner hull of a submarine, assuming the plating to be 3/8-inch and 7/8-inch medium and high tensile steel, respectively. Even when fired at 30° obliquity, and assuming the projectiles tumble after penetrating the outer hull so as to strike the inner hull lengthwise, the 50 caliber and 13mm AP projectiles will pierce both hulls within a range of at least 100 yards.

13-18. After completing six more patrols, GROWLER was lost in action with all hands on 8 November 1944 while attacking a Japanese convoy in the central Philippines area during her eleventh patrol. Information furnished by HAKE (SS256) and HARDHEAD (SS365), both of whom were operating with GROWLER at the time, indicates that the loss possibly occurred either as a result of enemy depth charging or the malfunctioning of one of GROWLER's own torpedoes. During her first ten patrols GROWLER sank 17 ships for a total tonnage of 74,900, and damaged 7 ships for 34,100 tons.

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Photo 13-1: GROWLER (SS215). General view looking forward at collision damage to bow. Section forward of frame 4 is bent 90 degrees to port. This protruding structure increased difficulty of maintaining submerged control of ship.

Photo 13-2: GROWLER (SS215). General view from starboard forward showing collision damage to bow.

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Photo 13-3: GROWLER (SS215). Port side view in Moreton Drydock, Brisbane. Most of damaged bow has been removed. Note absence of damage to the torpedo tubes and their outer doors.

Photo 13-4: GROWLER (SS215). 13mm machine gun projectile holes, bridge and conning tower fairwater, starboard side. This plating is only 5-pound and 10-pound medium steel. 25-pound and 30-pound STS plating was later installed on all fleet type submarines for the protection

--145--


Photo 13-5: GROWLER (SS215). View of conning tower upper hatch, showing 13mm projectile hole (1/2" x 3/4").

Photo 13-6: GROWLER (SS215). View showing damage to No. 1 periscope shear trunk in bridge "covered wagon". Arrows point to the two gouges made by 13mm projectiles. The periscope was jammed by these gouges, so that it could not be trained, raised or lowered. However, the periscope tube itself was undamaged.

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Photo 13-7: GROWLER (SS215). Upper horizontal section of prefabricated bow being erected. Lower section already welded in place. Ship is in Moreton Drydock, Brisbane.

Photo 13-8: GROWLER (SS215). Undocking from Moreton Drydock on 1 May 1943 with the new bow completely installed.

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SECTION XIV

U.S.S. DRAGONET (SS293)

Grounding While Submerged

Off Matsuwa To, Kurile Islands

15 December 1944

Class

SS285

Builder

Cramp Shipbuilding Co., Philadelphia, Pa.

Commissioned

6 March 1944

Length (Overall)

311 ft. 8 in.

Beam (Extreme)

27 ft. 3-1/4 in.

Submergence Depth (Designed Maximum) (Axis)

400 ft.

Displacements

Standard

1525 tons

Emergency Diving Trim

2050 tons

Submerged

2414 tons

Draft (Mean, Emergency Diving Trim)

16 ft. 10 in.

Type of Propulsion

Diesel Electric Reduction Drive

Main Engines (4)

Fairbanks-Morse 38-D-8-1/8

Main Motors (4)

Elliott Co.

Main Generators (4)

General Electric Co.

References:

(a) C.O. DRAGONET conf. ltr. SS293/A16 of 20 December 1944 (Report of War Patrol Number One).
(b) CO. DRAGONET secret ltr. SS293/A2-11/L11-1, Serial No. 1 of 26 December 1944 (Report of Damage Due to Grounding).
(c) Comdt.Navy Yard Mare Island conf. ltr. SS293/S11-1(360-718391) of 19 March 1945 (Supplementary Report on DRAGONET Grounding Damage).

Photographs Nos. 14-1 through 14-8 (furnished by Navy Yard, Mare Island).

PLATE XIV

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14-1. On 15 December 1944, during her first war patrol, DRAGONET holed and flooded her forward torpedo room as a result of striking an uncharted reef while running submerged off the Kurile Islands, and sank to the bottom in about 90 feet of water. DRAGONET was able to surface only after expelling the water from the torpedo room with salvage air, and she made the run back to base, through heavy weather, by continuing to maintain an air bubble in the damaged compartment. Although this case cannot be said to have resulted directly from enemy action, it has been included in this collection of war damage experiences to illustrate the problem of a submarine having one end compartment flooded while submerged. It is considered quite possible that other and less fortunate U.S. submarines during World War II may have received damage from enemy action, mines, ramming or grounding, which resulted in the flooding of an end compartment, and that the loss of these vessels may have been caused thereby. This report is based on the information contained in the references and on an informal interview with the then Commanding Officer. The Photographs were furnished by Navy Yard, Mare Island. The PLATE was prepared by this Bureau from data contained in the enclosures to reference (c).

14-2. On 9 November 1944, DRAGONET departed Midway for her first war patrol and on 17 November reached her assigned patrol area in the Sea of Okhotsk and along the Kurile Islands chain. For the next 28 days, until the grounding on 15 December, DRAGONET searched her area thoroughly but no enemy ship contacts worthy of torpedo fire were made. Weather conditions were extremely adverse during this period and strong currents and tide rips were experienced when operating close offshore or between islands.

14-3. During the early morning hours of 15 December, DRAGONET was conducting a surface patrol in an area slightly to eastward of the Kuriles chain. It was planned to submerge at daylight at a point about five miles south of the town of Yamato Wan on the east coast of the Island of Matsuwa To and to patrol across the southern approaches to this anchorage. Study of available hydrographic information indicated that navigational hazards in this area existed only close inshore. At 0515 DRAGONET submerged in Rashowa Strait to a depth of 100 feet in order to trim the boat. Although the sea was flat calm there were pronounced tide rips which rendered depth control difficult.

14-4. At 0717, in a position six miles south of Matsuwa To, DRAGONET was returning to a depth of 100 feet after a periscope observation at 63 feet, and had reached a depth of 70 feet, when a slight jar forward was felt. At this time the boat was running counter to the current in Rashowa Strait on course 090° (T) and had just rung up a change from one-third speed (1-1/2 knots) to two-thirds speed (4 knots). When the jar occurred, the ship had probably reached a speed of only about 3 knots and since observations had indicated that the current was about 2 knots, DRAGONET was probably making only about 1 knot over the ground. A dive angle of about two degrees was being carried. Immediately after receiving the jar forward, the boat assumed a three degree up angle and started to rise.

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14-5. The first reaction on DRAGONET was that a plane or small patrol craft, not seen by periscope, had located the boat and was dropping depth bombs or charges. Reference (b) states that "the feeling was much the same as experienced during depth charging when explosions are not very close". Enemy aircraft bombing was entirely possible, for visibility was unlimited, flying conditions were excellent and DRAGONET was only about 12,000 yards distant from a known seaplane base on Matsuwa To. Available information also indicated that there might be a military air base on the southeast side of the Island.

14-6. Following this reasoning, it was decided to seek safety in depth as quickly as possible and by the time the boat had risen to 58 feet, the negative tank was flooded, a two degree dive angle was ordered and emergency speed was rung up. These actions enabled the boat to gain depth rapidly but when 90 feet was reached, only 10 or 15 seconds after receiving the first slight jar forward, a series of heavy jolts accompanied by loud noises shook the entire boat and caused it to lurch violently. DRAGONET's speed at this time is estimated to have been about 6 or 7 knots by shaft turns, or about 4 or 5 knots relative to the bottom. This second and violent jolting was also at first interpreted as another depth charge or bombing attack and orders were issued to proceed to 150 feet and rig the ship for depth charge. Almost immediately afterwards, however, it was noticed that the boat was hanging at a depth of 92 feet with a dive angle of 20 degrees, the log recorded zero speed, and further jars occurred forward accompanied by loud grinding sounds. It was then realized that the boat had gone aground on a submerged reef or pinnacle and both shafts were stopped at once. The ship had no appreciable list at this time.

14-7. At about 0718, directly after the second grounding had occurred, word was received in the control room that the forward torpedo room was flooding rapidly (PLATE XIV). The collision alarm was sounded and the forward torpedo room was ordered abandoned. Only four members of the crew were present in that space and they promptly retired to the forward battery compartment. A watertight boundary was immediately established at the after bulkhead of the forward torpedo room by closing the bulkhead door and the bulkhead supply and exhaust ventilation flapper valves. Salvage air (225-pound) was then bled into the torpedo room through the bulkhead connection in an effort to halt the flooding, but was secured when the pressure within the compartment had reached about 55 pounds per square inch. Shortly afterwards, word was received in the control room that the torpedo room was "completely flooded". Complete flooding could not have occurred, however, since the rupture in the compartment was just above the watertight deck flat, allowing air to be entrapped in the overhead, and it is presumed that this report was made after the water passed over the top of the sight glass in the bulkhead watertight door. Later inspection disclosed that the water level in the compartment reached a height of about 1 foot above the upper bunks, or about 1-1/2 feet below the overhead of the torpedo room. Since a clock located just below the maximum flood line in the torpedo room stopped at 0720, it appears reasonable to assume that flooding of that space took place in approximately two minutes or less.

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14-8. As DRAGONET was pounding violently and lurching with the surge of the current at this time, it was feared that further serious damage would be sustained and that the hull might possibly break up unless the ship were quickly taken off the rocks. Word was passed to all hands to obtain objects that would float in case the boat might have to be abandoned. At about 0721, 3 minutes after the grounding occurred, the first attempt was made to get off the bottom. All main ballast tanks were blown plus bow buoyancy, negative and safety tanks. Nos. 3, 4 and 5 fuel ballast tanks were empty of oil but due to unfavorable sea conditions had not yet been converted to main ballast tanks by removing the riser blanks, and therefore were not blown since subsequent rapid venting, if the boat were required to again submerge, would have been impossible.

14-9. The increase in buoyancy resulting from the blowing of the main ballast tanks caused the stern of the boat to rise to the surface but the bow remained either on or near the bottom, due to the flooded compartment forward.1 When the stern rose, it acquired sufficient momentum to considerably overshoot its point of static buoyancy and surged out of the water far enough to project the extended No. 2 periscope above the surface for a second or two. The Commanding Officer had time only to make a partial sweep to port, but this brief observation disclosed that all was clear in the direction of Matsuwa To. The stern then settled back in the water until it reached its equilibrium point for the static buoyancy condition, the boat assuming a down angle of about 30 degrees. Since both periscopes went under the surface, no further observations could be taken.

14-10. As the stern was protruding out of water and therefore might be sighted by the enemy, and the bow could still not be raised due to the loss of buoyancy forward, all tanks were again flooded to submerge the ship. This action was taken at about 0730. DRAGONET once more settled to the bottom, in a depth of about 92 feet and with a 16 degree down angle. The ship's heading had now swung from 090° (T) to 110° (T) and the action of the current once again caused DRAGONET to pound heavily on the reef. It was thought at this time that perhaps the bow had been prevented from rising by being wedged in the rocks, so a brief attempt was made to back clear of the reef using emergency power. This proved unsuccessful, however, and the plan was abandoned.

14-11. At 0732 a report was received that the 55-pound per square inch air pressure which had originally been built up in the forward torpedo room had now diminished to 40 pounds and that the water in that compartment was below the eyeport in the bulkhead door and continuing to recede. A few minutes later, air could he heard blowing outside the torpedo room hull, indicating that the water level in the compartment had been lowered to the point of rupture and the down angle on the boat began to decrease slowly. The order was then given to blow the forward main ballast tank group, bow buoyancy, safety and negative tanks. As this caused the ship to trim by the stern, the after group of main ballast tanks was then blown. The ship rose slowly and surfaced at 0738, in clear sight of the shore establishments on Matsuwa To. When 26 feet was reached, the upper conning tower hatch was opened and the tanks were then blown with the low pressure (10-pound) air system as in any normal surfacing.


1 For further discussion see paragraph 17-16.

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14-12. All four main engines were started immediately and the area was cleared as rapidly as possible by proceeding south at emergency speed. All automatic weapons were manned and ammunition was broken out. Fortunately, no enemy interference was experienced as DRAGONET retired. Course was then set for Midway, the nearest Allied base.

14-13. The boat was only slightly down by the head on surfacing but was reported to have assumed about 15 degrees port list, for ruptures in the outer plating of port MBT Nos. 6B and 6D prevented those tanks from being blown below a few feet from the tank tops. Steps were taken immediately to increase freeboard, to reduce trim by the head and to correct the excessive list. Flood valves on Nos. 3, 4 and 5 fuel ballast tanks, both port and starboard, were opened and these tanks were blown in order to increase freeboard. MBT No. 6A and FBT No. 3A on the starboard side were then made free-flooding to compensate for the 15 degree port list. All variable tanks were pumped dry with the exception of No. 3 auxiliary, which was flooded as an additional list correction, and after trim tank, which was left about 3/4 full in order to add weight aft. No. 6 normal fuel oil tank was put on service to add weight aft by displacing fuel oil with heavier sea water. Air pressure was maintained on the forward torpedo room through the salvage air system and this kept the water within the damaged compartment at a low level. The after bulkhead of the torpedo room held tight with the exception of a few minor electrical cable stuffing gland leaks.

14-14. Heavy seas and high winds built up on 16 December. The bow planes were still rigged out and pounded so heavily that the entire ship vibrated and it was feared that further serious hull damage forward might result. A slight air leak developed around the top of the bulkhead door to the forward torpedo room but did not become serious. One of the bulkhead cable packing gland leaks increased somewhat, allowing water to enter the pantry. The gland nut was located in such a position that it was inaccessible and could not be tightened. When the grounding occurred and the forward torpedo room flooded, the Mk. 18 electric torpedoes in tubes Nos. 1 and 4 were in a partially withdrawn position for charging. Consequently, the inner doors of these tubes were open and the outer doors were closed but not locked. As the water level in the torpedo room was noted to be rising during this period of heavy weather, and salvage air had to be used in increasing quantities to maintain the air bubble in the torpedo room, it was believed that air must be leaking through one or both of the torpedo tube outer doors. Both high pressure air compressors had to be run continuously to provide sufficient salvage air. The three air banks on service were never allowed to drop below 2500 pounds pressure while the two emergency banks were kept at full pressure.

14-15. By 1800, the storm had increased in intensity. In order to decrease the draft forward and, therefore, the water level in the torpedo room, the contents of NFO tank No. 1 were blown aft into FBT Nos. 5A and 5B. During this transfer, DRAGONET developed a 20 degree port list, indicating that most of the water and oil in NFO No. 1 had ended up in FBT No. 5B, the port tank. The list shortly

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decreased to about 10 degrees but the ship commenced to roll heavily, reaching a maximum of 40 degrees to port. Compensation was accomplished by opening the floods of FBT No. 5B and blowing its contents to sea but this apparently over-corrected the list, for No. 3 auxiliary tank was then pumped dry.

14-16. By morning of 17 December the seas had abated somewhat, the bow was riding higher and the water in the forward torpedo room was down to about 12 inches above the floor plates and appeared to be maintaining this level. However, the bow planes were still pounding heavily. It was therefore decided to attempt to enter the forward torpedo room to rig in the planes, tighten up the torpedo tube outer doors and to determine the extent of damage.

14-17. A party of three officers and two men entered and secured the forward battery compartment. Rescue breathing equipment and "lungs" were carried in case chlorine gas might be generated should sea water inadvertently enter the battery cells from the forward torpedo room. Air pressure was built up in the battery compartment by the salvage air system and the control room bulkhead was then inspected and found tight. The small line to the salvage air gauge for the torpedo room was then disconnected in order to equalize the pressure between the two forward compartments. Bulkhead flapper valves in the hull ventilation system were not opened to accomplish this for fear they could not be securely closed again. When the pressure between the compartments had equalized, the bulkhead door was opened and the party entered the forward torpedo room. As the water level in that compartment was well below the bulkhead door, no water entered the battery compartment and the rescue breathers and "lungs" were discarded. By working in relays, the bow planes were rigged in by hand and the torpedo tubes were secured. The air in the torpedo room was foul with oil fumes so oxygen was bled into the compartment to improve working conditions.1 When the bow rose in the seaway, daylight could be seen through a ruptured area in the pressure hull plating, centered at frame 23, port side, just above the top of the forward trim tank. This was the first positive information that any of ship's company had as to the nature of the damage causing the flooding. Upon completion of the work, the torpedo room was again abandoned and sealed, and the air in the forward battery compartment was bled into the control room. The success of this well-executed and potentially hazardous operation for the safety of the ship removed many of DRAGONET's difficulties. The bow planes were subsequently further secured by running chains through the rigging gear quadrants in the superstructure.

14-18. Heavy seas and winds of gale force were again encountered late in the evening of 17 December and continued until the afternoon of the next day. At 0245 on 18 December, with the seas approaching from the starboard quarter, DRAGONET took a very large roll to port and "hung"

The introduction of pure oxygen into a compartment containing strong petroleum vapors is a potentially dangerous expedient, for it may result in an explosive mixture which will ignite upon the introduction of a spark or open flame. The safest procedure in a case of this nature is to don rescue breathers or "lungs" when oil fumes become objectionable.

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at an extreme angle for an appreciable period of time. This roll was measured on the clinometer in the control room as 63 degrees.1 Men were thrown from bunks and mercury spilled from the flotation chamber of the master gyrocompass, completely disabling it. Seas filled the port side of the bridge, but fortunately did not reach the upper conning tower hatch. The rudder was put at full left and the ship's heading was swung through 105 degrees before the ship slowly came back to about 20 degrees port. list. When MBT No. 6A and FBT No. 3A were vented, the ship came upright again, indicating that the flood openings of these tanks may have become exposed by the coincidence of a deep wave trough at the extreme roll, allowing the water within to escape and causing air pockets to form. Both MBT No. 6A and FBT No. 3A had been previously flooded to compensate for the port list which DRAGONET had assumed on surfacing.

14-19. DRAGONET arrived at Midway on 20 December 1944 and was docked the same day in ARD8 for inspection and emergency repairs. Temporary patches were installed over the holes in the forward torpedo room pressure hull and the outer plating of MBT Nos. 2B, 6B and 6D. The ship departed Midway on 23 December for Navy Yard, Mare Island, and arrived on 4 January 1945. Complete repairs together with many outstanding alterations were accomplished there and DRAGONET was returned to service on 26 March 1945.

14-20. Structural damage due to grounding was found to have occurred in five different areas along the hull, these being designated hereinafter as damages "A", "B", "C", "D", and "E". The location and nature of each damage is shown in PLATE XIV and Photos 14-1 through 14-8. PLATE XIV also indicates the extent of structural replacements in way of the damaged areas which were accomplished by Navy Yard, Mare Island, to effect permanent repairs. It should be noted that all of the structural damage areas, with the exception of damage "A" and "B" at the bow, occurred along the port side of the ship at about maximum beam of the ship at each point and that no damage was sustained by the keel or adjacent structure. This indicates that the ocean floor itself was soft and that the damage was caused by DRAGONET striking the horizontal promontories of an outcropping of rock.

14-21. In connection with damage at "B" (Photos 14-1, 14-2, and 14-3). it was at first believed that the lower torpedo tubes, and possibly the entire nest of tubes, were out of line. However, when the ship was docked at Mare Island, bore gaging and a careful inspection disclosed that no damage or misalignment of the tubes had occurred. The damage at "C" to the single (pressure) hull plating (37.5-pound HTS) caused the flooding of the forward torpedo room (Photos 14-1, 14-4, and 14-5). Since that compartment was flooded for several days, most of the electrical equipment within had to be replaced and all of the ordnance gear had to be overhauled. Damage at "D" (Photo 14-6) was extensive to outer shell plating but no deformation occurred in the inner hull. The outer hull was breached in only one place in this area, a 12-inch crack at frame 49 below the bilge keel (Photo 14-7) in way of MBT No. 2B. The damage at "E" (Photo 14-8) ruptured the outer shell plating of MBT Nos. 6B and 6D at about the mid-height of each tank. Since these tanks could be blown down only


1 For further discussion see paragraph 17-7.

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to the point of rupture, the resulting off-center water loading caused the ship to assume a port list upon surfacing.

14-22. The 37.5-pound HTS shell plating of the forward torpedo room, which was ruptured over a wide area as a result of the grounding, (damage "C"), was cut out of the ship in one section (Photo 14-4) and sent to the Industrial Laboratory of the Navy Yard, Mare Island, for examination and testing. The mode of fracture (Photo 14-5) had suggested that possibly this plating on DRAGONET possessed insufficient ductility or other undesirable qualities. Physical tests and chemical analysis on seven HTS samples from the damaged area, however, indicated that all complied with the requirements of Navy Department Specifications 48-S5-(INT). Although the granular appearance of the torn edges suggested that the crystalline structure of the HTS plating might have been large, a comparison with another specimen of known quality demonstrated that the damaged HTS was similar to that in general use. It appears, therefore, that the material was sound and failed as a result of heavy concentrated loading when that area of the hull struck a rocky promontory, although the low temperature of the water, 29° F., may have been a contributing factor.1

14-23. DRAGONET's experience illustrates several pertinent matters. First, the great value of the internal salvage air system as fitted in U.S. submarines was once again demonstrated. Second, the damage which occurred to DRAGONET represents the best available example of what should be expected when a modern heavy-hulled submarine grounds forward on a hard reef while running submerged at low speed. With the trend in submarine design now tending toward increased operating depths and higher submerged speeds, it is considered likely that more instances of this nature will occur in the future. Third, this case clearly demonstrates the fact that a submarine on the bottom, with an end compartment flooded, can be brought to the surface in a horizontal attitude only if the longitudinal center of buoyancy resulting from tank blowing is very close to the longitudinal center of gravity. If this condition is not satisfied, only the light end will rise and the ship will assume a spar buoy position, as was the case with DRAGONET on her first attempt to surface. The most obvious method of longitudinally balancing a submarine in such cases is to eject that water which is responsible for the off-balance condition by any means available, usually the salvage air system. This was the method used by DRAGONET which permitted her to surface on her second attempt. If dewatering is found impossible, then longitudinal moment balance may be achieved by flooding the compartment at the opposite end of the ship and/or by flooding and blowing only such a combination of internal and external tanks as will offset the moment of the originally flooded compartment and yet provide the maximum reserve buoyancy possible. On DRAGONET,


1 For further discussion see paragraph 16-25.

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for example, if all external tanks aft of and including the No. 6 MBT groups had been left flooded and the after trim tank and after WRT were completely filled, the ship could then have been surfaced, even though the torpedo room was completely flooded, by blowing the amidships and forward MBT, FBT and variable tanks. This loading would have resulted in a reserve buoyancy after surfacing of about 300 tons, or only about 50 tons less than the emergency diving trim condition. It should be noted that normal fuel oil tanks are also available for blowing should such be considered desirable or necessary to achieve longitudinal moment balance.

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Photo 14-1: DRAGONET (SS293). General view looking aft on port side, showing damaged areas resulting from grounding.

Photo 14-2: DRAGONET (SS293). View from port side showing damage "B" to torpedo tube shutters and fairing structure.

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Photo 14-3: DRAGONET (SS293). View from starboard side showing damage "B" to torpedo tube shutters and fairing structure. No misalignment occurred to torpedo tubes.

Photo 14-4: DRAGONET (SS293). View showing close detail of damage "C" to port pressures hull plating (37.5 pound HTS) of forward torpedo room. Small section of plate has been removed for test.

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Photo 14-5: DRAGONET (SS293). View taken from interior of forward torpedo room looking down and to port, showing close detail of typical fracture in pressure hull plating (37.5 pound HTS) at damage "C".

Photo 14-6: DRAGONET (SS293). View showing damage "D" in way MBT Nos. 2B and 2D. Although considerably deformed, the outer shell plating above the bilge keel was not ruptured.

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Photo 14-7: DRAGONET (SS293). View showing 12 inch vertical crack in A-strake, below bilge keel, at frame 49 in way of MBT No. 2B outer shell plating.

Photo 14-8: DRAGONET (SS293). View of damage "E" showing rupture and deformation of outer shell plating of MBT Nos. 6B and 6D at wing bulkhead 85 dividing the two tanks. Flooding of these two tanks caused boat to assume 15 degrees port list on surfacing.

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Plate XIV: Damage from Grounding While Submerged


SECTION XV

BEHAVIOR OF UNDERWATER NON-CONTACT EXPLOSIONS

15-1. The principal Japanese anti-submarine weapons were the depth charge and bomb, both designed to achieve their destructive effect by non-contact underwater explosion in close proximity to the target. An explanation of the behavior of such non-contact underwater explosions has therefore been included in this report.

15-2. The action of an explosive is the result of a purely internal chemical conversion which liberates a large quantity of gas and heat within a very short period of time. The total quantity of energy produced by the detonation of a conventional explosive is much less than that given off by combustion of equal weight of any of the standard fuels. However, the rate at which the energy is released, due to the velocity with which the reaction travels through the explosive, is very much greater. Detonation is an action characteristic of high explosives. Substantially complete and virtually instantaneous transformation of a high explosive charge into energy and decomposition products is called a "high order" detonation. All underwater explosive weapons are intended to detonate high order.

15-3. The sequence of events which occurs in the water as the result of an underwater explosion is of considerable interest. When a high explosive material, such as used in a depth charge or depth bomb, is detonated underwater, the initial action that occurs is the creation of a detonation wave which travels through the explosive material at a very high velocity, approximately 20,000 feet per second, and converts the solid charge to a dense gas at a high temperature and pressure without appreciable change in volume. It has been estimated that the initial pressure of the gas bubble resulting from underwater detonation of explosives having properties similar to TNT is of the order of one to two million pounds per square inch. Under this tremendous initial pressure, and considering the detonation to have occurred at a sufficient depth so that surface effects do not appreciably alter the subsequent phenomena, the gaseous product of the detonation then suddenly starts to expand, suddenly compresses the water around the charge, and thereby sets up in the water a shock wave. The shock wave consists of the shock front, which is a discontinuity of pressure typified by an almost instantaneous pressure rise, followed by an approximately exponential decay of pressure with time and by, theoretically at least, a long tail of pressure too low to be of practical interest (Figure 15-1). This shock wave travels faster than the subsequent expansion of the gas bubble, leaves the vicinity of the explosion and is propagated radially outward in all directions (Photo 15-1). Except for the regions of very high pressure in the immediate vicinity of the explosion, the shock wave obeys the laws of spherical propagation of sound reasonably well, i.e., as the wave advances its peak pressure falls off a little faster than the inverse of the distance from the center of the explosion, the positive time duration of the pressure pulse increases slightly with increasing distance, and the wave travels only a little faster than the speed of sound in water (about 4900 feet per second). The water, after the wave has passed, remains substantially undisturbed. This initial shock wave or pressure pulse, the positive pressure portion of which lasts for only a few milli-seconds in passing any particular point as it travels radially outward, is believed to account for the major portion of the destructive effect of a

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close underwater detonation and all of the remote action or destructive effect of a distant underwater detonation. When received from a considerable distance, the shock wave is discernible as a "metallic ping" on a submarine pressure hull. In a general way, the cause of damage to a ship from underwater explosions may be thought of as the sudden delivery at the ship of energy at high potential, i.e., the energy delivered by the shock wave. The energy contained in the primary shock wave is approximately one-quarter of the total energy released by the detonation of the explosive charge.

15-4. Simultaneously with the dispatch of the shock wave, the enormous initial pressure created by the transformation of the explosive charge into gas imparts a high velocity in a radial direction to the surrounding water and the gas bubble starts to expand outward with an initial velocity greater than that of an ordinary gun projectile. The kinetic energy thus imparted in mass flow to the water may be a significant damaging factor in very close explosions but is otherwise of only academic interest since the water velocity falls off rapidly with distance from the center of the explosion. Because of the high momentum imparted to the water, the bubble expansion continues beyond the point at which the gas pressure within equals the absolute hydrostatic head of the surrounding water and atmosphere. Eventually, however, the opposing external hydrostatic pressure brings the expansion to a halt, the pressure within the bubble at this point being of the order of only a few pounds per square inch, and reversed flow of water commences inward toward the center of the gas bubble. The gas pressure then increases rapidly as the size of the bubble diminishes, but the motion again overshoots the point of hydrostatic equilibrium due to the inward momentum of the water. At the extreme compression on this first contraction the gas pressure within the bubble reaches a peak estimated to be about 10,000 pounds per square inch. This high pressure initiates a second pressure wave or pulse in the surrounding water, having maximum intensity at the time of minimum bubble diameter. While of considerably less intensity than the initial shock wave, this second pressure wave is of many times greater duration and consequently may be a significant damaging factor to some types of targets.

15-5. The cycle of expansion and contraction may then repeat several more times in the manner described above until all of the energy has been dissipated or the bubble has either vented itself by breaking the surface of the water or has broken up into numerous small bubbles of no consequence. Due to energy losses, the bubble oscillations rapidly dampen out, successive maximum bubble sizes becoming smaller and successive minimum bubble sizes becoming larger. With each succeeding contraction, pressure waves or pulses of progressively decreasing intensity will be emitted. Photo 15-2 is an excellent high-speed camera study of gas bubble oscillations produced by the underwater detonation of a No. 8 blasting cap, roughly equivalent to 1/2 gram of tetryl. Figure 15-1 below depicts the phase relationship between the gas bubble oscillations and the pressure waves.

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15-6. A secondary effect associated with an underwater explosion, which may in certain circumstances be of importance, is that of pressure wave reflection from the surface or from the bottom. If an explosive charge is detonated at a location such that either the sea surface or the bottom is at a distance comparable to or less than the distance to the target, then reflected waves from either the surface or the bottom may greatly intensify or diminish the direct pressure wave at the target by interference. The pressure wave is reflected from the sea surface as a tension wave, subject to the restriction that water can support only a limited negative pressure prior to the occurrence of cavitation. If the detonation is shallow, surface reflections can therefore very materially diminish the main pressure pulse by interference. However, if the detonation occurs close over a hard ocean floor, i.e., rock, sand, etc., the pressure pulse upward and to the sides will be considerably increased over that for a similar detonation in free water where the ocean floor is relatively distant, the amplification being caused by reflection of energy from the hard bottom. The pressure pulse will theoretically be doubled for charges which are detonated on a perfectly rigid surface. This factor would appear to operate in favor of anti-submarine forces attacking a target running close to hard ocean floors.

15-7. The surface phenomena over an underwater explosion is of interest. Three distinct effects can be noted under certain conditions.1

(a) Almost simultaneously with the explosion, the surface of the water is agitated by the pressure wave and a light spray may be thrown up. This effect is not noticeable if the explosion is very deep.

(b) During the first second or two after a shallow explosion, the water rises in a flattish "dome" which is often white in color and may attain a height of 50 feet or more. As the depth of the explosion is increased, the maximum height of the dome diminishes, and finally, at relatively great depths, no dome is formed (e.g., there is none from 300 pounds of TNT 150 feet deep).

(c) Plumes of spray may be thrown up by the gaseous products of the explosion venting through the surface. If the charge is only a few feet below the surface, the plumes break through the dome while the latter is still rising, and may attain a height of many hundreds of feet. As the depth of the explosion is increased, the plumes become less marked and also appear later; they may break through the dome at the instant the latter has attained its greatest height, or when it is sinking again, or the plumes may not appear until after the dome has disappeared. Finally, at great depths, no plumes are formed, but a minute or so after the explosion a mass of creamy water pours up to the surface.

15-8. The phenomenon of repeated impact blows resulting from single underwater explosions, due to the intense pressure waves created by succeeding bubble contractions, was frequently noted by submarine personnel during the war.2 The outflow of water ahead of the expanding gas bubbles has also been commented on in numerous war patrol reports, being typically described as a "rush" of water about the ship or through


1 David Taylor Model Basin conf. Report No. 480 of October 1941.
2 Also observed as early as 1861 by Lt. Col. H. L. Abbot, USA, while investigating submarine mines for the Corps of Engineers, U.S. Army. Observed during TROUT (SS202) depth charge tests off Portsmouth, N.H. in 1941.

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Photo 15-1: German photograph showing gas bubble and shock front 0.000014 second after detonation of 30 milligrams of explosive similar to TNT. This photograph is the result of a double exposure, the first being taken before detonation to show the exact position and shape of the explosive charge.

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Photo 15-2. High speed photographic history of gas bubble oscillations resulting from detonation of a No. 8 blasting cap underwater. This series of photographs is from David Taylor Model Basin conf. Report No. 512 of May 1943.

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the superstructure which could be distinctly heard inside the pressure hull after depth charge attacks. There are many cases on record where submerged submarines have been forced up or down due to these water movements, occasionally by as much as fifty feet. For example, during her fourth war patrol, BALAO (SS285) was forced down from 390 foot depth to 590 foot depth by a series of close depth charge detonations, each detonation causing the boat to increase depth by about 20 or 30 feet. HAWKBILL (SS366), in her action of 18 July 1945, was forced up from periscope depth by depth charges detonating under the hull and broached with a 20 degree up angle, exposing 60 feet of the bow. Various submarines have been heeled over by underwater explosions. GRENADIER (SS210), for example, reported a 10 to 15 degree heel as a result of a close bomb detonation (paragraph 8-5). The following description of depth charge detonations have been excerpted from various U.S. submarine war patrol reports and are representative of how such explosions sound to submarine personnel. BLUEGILL (SS242), while being depth charged at 340 foot depth on her third patrol, reported "The characteristics noted on far depth charges . . . were first a detonator click . . . and then bang!" BLUEGILL also described the more distant explosions as "a deep rumble increasing to the final boom." CABRILLA (SS288), while being depth charged at about 350 foot depth on her fourth patrol, reported "On almost all depth charges the familiar small detonation was followed by a large explosion and then swishing and falling waters were very evident". SALMON (SS182), while being depth charged at 150 feet depth during her first war patrol, reported for relatively distant depth charges that "As each charge went off there would be two pings on the hull which sounded as though two small nuts had been dropped, then after a period of one to two seconds the depth charge would be heard". FLYING FISH (SS229), depth charged at 250 foot depth during her second patrol, compared a depth charge detonation to a "thud similar to that expected when a 100-pound weight is dropped on the hull" followed shortly by the sound of the explosion and then "water would be heard rushing through the superstructure". PARGO (SS264), depth charged at about 350 foot depth during her fourth patrol, reported depth charge detonations which "rocked the boat in three separate and distinct pressure waves" and with a sound effect of "whoom -- whoom -- BO-om." Others described the sound of depth charges exploding in the distance as like a child playing with a toy hammer, very mild and weak, and the sound of fairly close charges as a "hard metallic click-bang". The metallic "click", "thud", or "ping" may be interpreted as the mechanical response of the hull structure to the arrival of the pressure pulse from an explosion and should have been distinguishable from the subsequent audible frequencies generated by the explosion, i.e., the "bang" or "boom", only for an explosion relatively distant from the hull. The increment of time between the arrival of the pressure wave and the audible frequencies will not be perceptible at very close ranges, the two arriving practically simultaneously. That this is so is evidenced by the fact that submarine personnel considered themselves safe if the "click" preceding the "boom" was distinguishable, since they found by experience that the depth charge would then detonate at a range which would not cause much, if any, damage. Contrary to the general impression, the pistols of Japanese depth charges contained no mechanism which could cause a "detonator click". The

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sound of "falling waters" referred to by CABRILLA was no doubt caused by the surface effects of the depth charge detonations, The "two pings" referred to by SALMON were perhaps due to a bottom reflection of the pressure pulse striking the hull shortly after the arrival of the direct pressure pulse.

15-9. The mechanics of damage by underwater explosions are not sufficiently well understood at this writing to permit precise evaluation of the relative effectiveness of the initial shock wave and each of the succeeding pressure waves in producing damage. It is known that for most practical situations, the initial shock wave of a non-contact underwater detonation can be considered the principal agent of damage. However, it has been demonstrated that under certain conditions it is possible for the additional pressure waves from succeeding compressions of the gas bubble to contribute further damage. For example, deep sea explosion tests by the Underwater Explosives Research Laboratory of the Bureau of Ordnance on small-scale (1/23) partial-length models, representing simplified SS285 Class submarine circular hull sections, showed that under combined hydrostatic loading (due to depth of the water) and explosive loading a well defined critical charge distance existed, such that at smaller distances general collapse of the test cylinder occurred whereas at greater distances only small local damage was observed.1 With the explosive charge just within the critical distance, it was found that general collapse did not occur until the arrival of the pressure pulse from the first contraction of the gas bubble. With the charge at approximately two-thirds this critical distance, however, the initial shock wave alone was of sufficient intensity and duration to cause collapse. It should be noted that due to the scale effect in interpretation of small model tests, the secondary pressure pulses from detonations of conventional depth charges and bombs in attacks on full size submarines would be somewhat less effective than indicated by the above tests.

15-10. For an explosion set off at a given distance from a circular submarine structure, secondary pressure pulses will have the greatest damaging effect when the charge is detonated below the hull.2 This is attributable to the tendency of the gas bubble to rise vertically under the influence of its buoyancy, especially in the contraction phase where relatively high velocities of ascent may be reached. It is therefore possible that the pressure pulse generated at the end of the first cycle of the bubble oscillation may be initiated close enough to the submarine to produce new or additional damage although the detonation itself was more distantly removed. Gas bubble oscillations resulting from detonations located near the side or above a submarine can generally be expected to rise and therefore increase their distance from the hull.


1 Office of Scientific Research and Development conf. Report No. 5417.
2 Both the Germans and French considered that for detonations occurring under a submarine, the limiting range within which serious damage could be expected would be double that for similar detonations located horizontally out from the side of the submarine--NavTechMisEu conf. Technical Report No. 227-45 of August 1945.

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For a charge which detonates relatively close to the side of a hull, however, vertical rise may be offset by the tendency of the gas bubble to migrate to the nearby rigid hull. Even for charges which detonate close above a submarine, the gas bubble may oscillate several times in very close proximity to the hull instead of rising.

15-11. Although considerable research and experimental work has been carried on by many nations, including the United States, in an effort to determine the damaging ranges of various anti-submarine non-contact explosive weapons, present experimental and theoretical knowledge is still not sufficient to compute accurate damage versus distance relationships for such weapons. The figures given by different investigators among various countries are considerably at variance. Unfortunately, the great amount of submarine war damage experience available to this country furnishes no precise quantitative information regarding the behavior of submarines when attacked with underwater non-contact explosives since the charge sizes, distances and relative points of detonation are not known in any of the cases. The damaging range for a given weight of specified explosive will of course vary widely among the different types of submarines, depending upon the energy absorption characteristics of the hull structure, the design and mounting of vital systems and machinery, and the circumstances of the attack, i.e., the orientation and distance of the charge with respect to the hull and the depth of submergence of the submarine.

15-12. A study of available data indicates that the detonation of 300 pounds of TNT will almost certainly cause pressure hull rupture and therefore presumed lethal damage when the center of detonation is within 25 feet of the pressure hull of a U.S. light-hulled submarine (SS284 and previous). Between 25 and 50 feet, rupture or marked permanent deformation of the pressure hull and/or serious damage to vital machinery and systems may generally be expected, depending upon the position of the charge relative to the hull and the submergence depth of the submarine. Moderate to minor damage to equipment and fittings can be expected from 50 to 100 feet and beyond. It appears that 40 feet would be a fair range to delineate the boundary between the zones of serious and moderate damage for 300-pound TNT charges used against U.S. light-hulled submarines at relatively shallow depths. The British estimated from their war experience that pressure hull rupture would be certain to occur on submarines of contemporary construction with the following combinations of explosive weights and ranges: 150 pounds of TNT at 14 feet; 300 pounds of TNT at 20 feet; 1200 pounds of TNT at 40 feet. German tests on U-446 in June and December of 1944 indicated that the detonation of 275 pounds of S1 explosive located 33 feet below the surface would cause marked permanent pressure hull deformation when within a distance of about 60 feet from the surfaced submarine.1 French calculations based upon research tests conducted in 1934 indicated that a double-hulled Paskal type submarine submerged to a keel depth of 50


1 NavTechMisEu conf. Technical Report No. 227-45 of August 1945. The German S1 explosive is similar in power to TPX.

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feet would sustain permanent pressure hull deformation from the detonation of a 440-pound charge (type of explosive not stated) when placed at approximately the same depth and closer than 50 feet to the pressure hull.

15-13. Figure 15-2 below contains a plot of the damaging-range curve developed by the Bureau in 1943 for light-hulled SS212 Class submarines (11/16-inch medium steel pressure hull) when subjected to non-contact underwater detonations of varying weights of explosives comparable in power to TNT. The data upon which this curve is based are sparse and incomplete and the accuracy of the curve should be regarded accordingly. Furthermore, it does not take into account the orientation of the charge with respect to the hull or the depth of submergence of the submarine, both of which have a marked effect on the range within which damage will occur. The region below the curve represents charge weight and distance relationships at which marked permanent deformation of the pressure hull and serious damage to vital machinery and systems may generally be expected. The curve should properly be thought of as a "band" rather than an exact line of demarkation. Included in the same figure is a second curve giving distances at which hull rupture can be expected to occur for target submarines having an assumed 7/8-inch high tensile steel pressure hull, equivalent to that of the SS285 Glass. This latter curve was developed by the Operations Evaluation Group from meager experimental evidence plus theoretical considerations and differs appreciably from the Bureau of Ships curve since it is based on positive rupture of a 7/8-inch thick HTS pressure hull rather than on permanent deformation only of an 11/16-inch thick MS pressure hull as in the case of the Bureau of Ships curve.1 The Operations Evaluation Group curve compares closely with the lethal ranges arrived at by the Underwater Explosive Research Laboratory after expanding the results of their small scale SS285 model tests (paragraph 15-9) to apply to a full size SS285 Class submarine (submerged to a depth of 50 feet).

FIGURE 15-2 DAMAGING RANGE CURVES FOR U.S. SUBMARINES (FOR SHALLOW SUBMERGENCE CONDITION ONLY)


1 Operations Evaluation Group conf. Research Report No. 40 of 28 April 1944.

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15-14. The effect of depth of submergence on the strength of submarines under dynamic loading (also termed pulse, shock or explosive loading) from non-contact underwater detonations is naturally a matter of much interest to both design and operating personnel. In the case of the SS285 Class small model tests cited in paragraph 15-9 above, the lethal distance of a given weight of explosive was observed to increase rapidly with depth. For example, the maximum charge distance at which cylinder collapse resulted was two and one-half times greater at 673 feet than at 200 feet.1 Qualitatively such an effect is to be expected, since the stress due to explosive loading is superimposed on that already present in the structure due to hydrostatic pressure and therefore the lethal distance should increase rapidly as the absolute hydrostatic collapsing depth of the hull is approached. In addition, marked permanent deformation of a pressure hull might be sustained from explosive loading at 300 foot depth, for example, without further collapse of the hull occurring due to hydrostatic loading, whereas at a greater depth the same degree of deformation could result in complete hull failure due to hydrostatic loading following the explosive attack. There is considerable question, however, as to the accuracy with which such small scale models represent full scale submarines in their resistance to underwater explosive attack.2

15-15. It is apparent that there is need for further research and experimental studies in order to determine the exact behavior of non-contact underwater explosions and their effect on present and projected submarines under every conceivable condition. It is considered that such studies would be principally of value for the optimum development and employment of underwater anti-submarine explosive weapons. In addition, however, further study of hull deformation short of rupture, and shock effects, should make possible continued improvement of the strength of submarine pressure hulls under dynamic loading, increased shock resistance of machinery and vital systems, and perhaps improved basic characteristics of submarines and their operating doctrine.

15-16. The question naturally presents itself as to what hazard, if any, exists in the possibility of close underwater explosions causing detonation of torpedo warheads when loaded in torpedo tubes having their outer doors open, or of the 50 caliber, 20mm and 40mm and 3, 4 or 5-inch fixed ammunition carried topside on submarines in pressure-proof ready service cases. It is known that projectiles and torpedo warheads are generally subject to detonation under the following conditions: (a) when subjected to the roasting effect of high temperatures applied for protracted periods of time (generally 15 to 30 minutes for TNT-loaded torpedo warheads); (b) when struck by high velocity fragments; sensitivity to detonation in this latter case being dependent upon the velocity of the fragment, the temperature of the fragment,


1 Static collapsing depth of these SS285 scale models was about 870 feet. 2 David Taylor Model Basin conf. Report C-SS/S1-8; C-S81-3 of March 1947.

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the wall thickness of the warhead or projectile concerned and the sensitivity characteristics of the explosive itself; and (c), sudden and violent crushing or pinching of the container walls of dent sensitive explosives. It is believed that condition (a) can be ruled out since even should the gas bubble from a nearby detonation envelop an exposed projectile or torpedo warhead while in a late stage of its expansion, the temperature of the gases would then be relatively moderate and the heat would not be applied for a sufficient length of time to cause detonation. Should the gas bubble make contact during its early and extremely high temperature phase, the point of detonation would then be so close to the hull that destruction of the ship would doubtless in any event occur.

15-17. With regard to condition (b) above, carefully conducted tests and the combined war experience of both submarines and surface ships indicate that for all practical considerations little to no hazard exists in this respect. It has been ascertained that high velocity fragment attack upon an exposed torpedo warhead or projectile will generally not cause detonation when the fragments pass through a few feet of water (4 ft. or more). This is due to the fact that fragment velocities are decreased so rapidly upon passing through the water as to become less than the critical velocity necessary for detonation of even a relatively sensitive explosive such as Torpex. For example, it has been demonstrated in a series of tests, that the detonation of a Mk. 13 mine (675 pounds TPX) would not cause the detonation of an AN-M64 GP bomb (262 pounds TNT) even though both were suspended only four feet apart in free water.1 In this case the bomb was completely enveloped by the gas bubble from the adjacent mine detonation and was also subjected to intense fragment attack. As another example, the British submarine HMS TRIUMPH, while proceeding on the surface on 26 December 1939, struck a floating contact mine almost directly under her bow.2 The resulting detonation demolished the forward 18 feet of the hull back to the muzzle doors of the lower torpedo tubes, and caused immediate flooding of the forward torpedo room plus other damage farther aft. Although the forward lower tubes were loaded with torpedoes, no warhead detonations occurred. No information is available as to whether or not torpedoes were loaded in the two bow external torpedo tubes, which on the TRIUMPH Class are located in the superstructure about ten feet forward of and four feet above the lower nest of four tubes, and therefore presumably would have been more heavily damaged. TNT-filled torpedo warheads are difficult to detonate by fragment attack since the required critical fragment velocity is very high. Numerous cases are on record where TNT-loaded warheads on destroyers have been punctured by strafing or fragment attack from close bomb hits without themselves detonating. Submarine torpedo warheads are currently being loaded with HBX-1, an explosive having a fragment sensitivity comparable to that of TNT.

15-18. Condition (c), detonation by sudden and violent crushing or pinching of the container walls of dent sensitive explosives, appears


1 Office of Scientific Research and Development conf. Report No. 4810.
2 ONI Attaché Report No. 992 of 4 September 1940.

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to offer definite hazard to exposed torpedo warheads when loaded with a relatively sensitive explosive such as TPX. This is due to the fact that the strength of the warhead container walls may not be sufficient to prevent crushing action under close underwater explosive attack. In GATO's (SS212) action of 1 April 1943, for example, the warhead of a torpedo stowed in one of the after tubes was severely crushed by a close depth charge attack aft (Photo 15-3). The tube was flooded at the time, with the outer door closed, but apparently the pressure waves from the depth charge explosions forced the outer door open slightly and thereby admitted full pressure to the warhead. It is not known whether the explosive charge in this warhead was TNT or TPX, both types being still in use by our submarines at this period of the war. If the filler had been TPX, there is appreciable likelihood that the warhead would have detonated and caused the loss of the ship. It appears that torpedo warheads containing dent sensitive explosives should be made of somewhat greater strength than the pressure hull so that destruction of the hull can be expected before appreciable deformation of the warhead container will occur. On GATO the pressure hull adjacent to the torpedo tubes was depressed by as much as 2 inches, indicating that the hull and warhead container were of roughly equivalent strength. Since HBX-1 is understood to have a much lower dent sensitivity than TPX, the hazard with HBX-1 torpedo warheads would be appreciably less. It should be noted that, under explosive attack, substantially the full effect of the attack may reach torpedo warheads even though the outer doors are closed, due to the possibility of gasket damage or fluttering of the door under successive pressure waves.

15-19. Several instances have been reported by U.S. submarines which would seem to indicate that luminous gases, visible shock waves or smoke from close underwater detonations may have entered the interiors of the ships concerned, either through packing glands or hatches which opened momentarily. ICEFISH (SS367) reported "Got to 420 feet just as a barrage of 4 depth charges of blockbuster intensity went off on top of us. The cordite fumes from these filled the conning tower and both periscope packing glands leaked so heavily the bilges could not accommodate the water. . ."1 On KINGFISH (SS234), an EM 2/c stationed in the motor room during the depth charge attack of 23 March 1943, reported: "I was looking at the stern tube as one of the depth charge bombs burst and a ball of fire came through the tube. It came through the stern tube in the shape of a blunt streak two feet wide and extended into the boat about 3 feet. It was an instantaneous streak, flash and it was gone. . . ."2 This phenomenon was also observed by one other witness. Also on KINGFISH, it was reported that two observers saw flame shoot out of one of the after torpedo tubes coincident with a close detonation in that vicinity.3 At the same time, the air pres-


1 C.O. ICEFISH conf. ltr. SS367/A16-3/(011) of 13 November 1944 (Report of War Patrol No. One).
2 Comdt. Navy Yard, Mare Island, Supplementary Report on KINGFISH War Damage, Appendix I (Statement of Witness to Flash through Starboard Stern Tube).
3 BuOrd (Re6) memo dated 4 May 1943, (Report on Inspection of KINGFISH Damage and Interview of Ship's Officers by Dr. A. B. Focke).

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sure in the tube was reported to have increased to 130 pounds per square inch and smoke and burned explosive fumes were detected in the after torpedo room. Several after torpedo tube inner door gaskets were slightly damaged. BREAM (SS243) reported ". . . men in forward torpedo room saw blue flame spurt into the room" during depth charging.1 BLUEGILL (SS242) reported "Forward torpedo room saw flame of exploding depth charges through torpedo loading hatch when it lifted off its seat during many explosions."2 GUITARRO (SS363) reported "Blue flame showed around the periscopes and the after engine room hatch" following mass detonation of an ammunition ship 1900 yards distant.3

15-20. The descriptions of the phenomena noted above are remarkably consistent with each other, although occurring under different conditions. The odor of smoke and explosion fumes could presumably be explained only by the gas bubble having been in contact with the vessel at some time during its history. The reports connect these odors with the first events of the explosion. The connection between the odors and the gas bubble becomes confusing when it is considered that the lethal distance of the average depth charge (300 to 600 pounds of TNT or equivalent) is greater than the maximum radius of the bubble (about 20 to 25 feet for the charges cited above at periscope depth, and about 12 to 15 feet at 300 foot depth), and particularly so when it is noted that the vessels sustained no damage of great consequence. It is possible that the bubble in a later phase may actually be involved in the reports of smelling fumes, since the period of oscillation of gas bubbles from depth charge detonations is about one half of a second under typical conditions, and such an interval of time may not have been distinguished in making the report.

15-21. The observations of flame are even more confusing, since they seemingly point to contact of the hull with a gas bubble while unexploded products are still in combustion, or at least while temperatures are still high. This would almost certainly be limited to the gas bubble in its first cycle. GUITARRO's experience suggests that the gas bubble may not be involved since in her case it was impossible for the bubble of the ammunition ship explosion to have come in contact with the submarine. Shock wave phenomena emanating from explosions in air can sometimes be visually detected by observers in the same media. It is perhaps possible that some similar visual effect may be transmitted from an underwater shock wave to the atmosphere within a submarine through slack packing glands or fluttering hatches and torpedo tube doors. For example, rapid expansion of saturated air upon the passage of a shock wave will pro-


1 C.O. BREAM conf. ltr. SS243/A16-4, Serial (03-45) of 22 March 1945 (Report of War Patrol No. Five).
2 C.O. BLUEGILL conf. ltr. SS242/A16-3, Serial 039 of 25 November 1944 (Report of War Patrol No. Three).
3 C.O. GUITARRO conf. ltr. SS363/A16-3, Serial 044 of 16 November 1944 (Report of War Patrol No. Three).

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duce momentary precipitation of water vapor and this would appear as an instantaneous light haze. Air within a submarine is generally at or near saturation when running silent with the air conditioning system secured. This explanation seems to be a relatively unlikely one, but is felt to be the most reasonable hypothesis which the facts reported, assuming them to be true, will support. It is not improbable that the reports of flame may have been due to vagaries of vision. It is known, for example, that slight changes in the pressure, volume or velocity of blood in the retina will cause some people to see momentary grayish or purplish luminous clouds that sweep over the field of vision. Others may see rivers of light or a succession of scintillations that resemble fireworks.

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Photo 15-3: View showing damage sustained by torpedo warhead on GATO (SS212) as the result of a close depth charge explosion aft in her action of 1 April 1943. Torpedo was stowed in an after tube, with the tube flooded and outer door closed.

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SECTION XVI

HULL DAMAGE AND STRENGTH

16-1. A thorough search of available records indicates that throughout the entire war there were but fifteen reported cases, excluding losses, in which permanent deformation of the pressure hull was sustained by U.S. submarines as the result of non-contact underwater explosions of bombs and/or depth charges. In none of these fifteen cases was the pressure hull ruptured or torn nor is there any instance on record where a U.S. submarine has survived pressure hull rupture which occurred through war damage while the vessel was submerged.1 This is to be expected since rupture of the pressure hull of a submerged submarine should normally be lethal inasmuch as the flooding of one or more main compartments will render submerged control impossible, and the boat must then either surface, where it probably would be destroyed by enemy action,2 or must proceed to the bottom. Even assuming the bottom to be at a depth less than the collapse depth of the pressure hull and compartment bulkheads, experience shows that, under war conditions, self-salvage of the boat or ultimate escape and survival of personnel is quite unlikely.3

16-2. In three of the fifteen cases where pressure hull deformation is known to have been sustained, the boats were damaged so extensively that they were subsequently scuttled by their own crews to prevent enemy capture.4 In the other twelve cases,5 the boats successfully evaded the enemy after receiving damage and returned to base. Ten of these submarines were repaired and returned to service while two6 were scrapped.


1 (a) DRAGONET's (SS293) forward torpedo room was holed as the result of striking a reef while submerged, but she was not under attack at the time. See Section XIV for DRAGONET narrative, (b) BERGALL's (SS320) pressure hull was torn open above the waterline by an 8-inch shell hit (dud). The vessel was on the surface when struck and returned to base running surfaced for the entire distance. See brief of damage in Appendix I (13 December 1944).
2 One such possible case is the loss of ARGONAUT (APS-1) on 10 January 1943. See brief in Appendix II.
3 The loss of TANG (SS306) on 24 October 1944 is the only known instance where personnel have made underwater escapes from a U.S. submarine sunk through war action.
4 PERCH (SS176), GRENADIER (SS210), and SCULPIN (SS191). See Sections IV and VIII for narratives on loss of PERCH and GRENADIER, and Appendix II for brief on loss of SCULPIN (19 November 1943).
5 GUDGEON (SS211), 26 January 1943; KINGFISH (SS234), 23 March 1943; GATO (SS212), 1 April 1943; TUNNY (SS282), 26 August 1943; GATO (SS212), 20 December 1943; SCAMP (SS277), 7 April 1944; CREVALLE (SS291), 14 May 1944; TUNNY (SS282), 1 September 1944; SALMON (SS182), 30 October 1944; HALIBUT (SS232), 14 November 1944; REDFISH (SS395), 19 December 1944; GREENLING (SS213), 25 January 1945. See narratives in Sections V, VI, VII, IX and briefs in Appendix I.
6 SALMON (SS182) and HALIBUT (SS232)

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16-3. Since the strength of submarine hulls is naturally a subject of great interest to both operating and repair personnel, a brief discussion of the elementary design criteria of such hulls, and their probable mode of failure, has been included below. The information has been obtained from the considerable investigations conducted by the David Taylor Model Basin and this Bureau.

16-4. Weight considerations are a determining factor in submarine design since the sum of the weights of the various components of the ship, i.e., hull, propulsion machinery, armament, control gear, etc., must equal the weight of the water displaced by the intact volume of the ship when submerged. It is apparent that weight saved by the use of an efficient hull structure can be utilized for the benefit of the other components or for further increasing the strength of the pressure hull to permit a greater operating depth. Submarine pressure hulls are therefore usually made circular for as great a proportion of the length as possible. For the sake of simplicity, in the preliminary design study of a projected submarine the diameter of the pressure hull can be considered as the principal variable determining the amount of weight which will be available for the various ship components. The length of the hull is usually fixed by the arrangement study, i.e., the space requirements of armament, stores, crew, propulsion machinery sufficient to achieve the desired surface and underwater speeds, etc. The diameter and length determine the submerged buoyancy which, after subtracting the weights of the other components, determines the amount of weight that can be utilized for the hull structure and therefore the collapse depth of the vessel. In actual practice, the preliminary design phase may consist of a series of studies to determine the effect of varying length, diameter, hull form, types of propulsion plants, arrangements, etc., on such operating characteristics as speed, range, and submergence depth, in order to achieve the best compromise possible. Once the diameter of a projected submarine and its operating depth (including a reasonable factor of safety) have been decided upon, the detailed structural design of the pressure hull can proceed.

16-5. Under external pressure, the collapse strength of a transversely framed cylindrical vessel of circular cross-section is determined by the physical properties of the structural material used for the shell, the shell thickness/diameter ratio (t/D), and the unsupported length between frames/diameter ratio (L/D). By varying these factors, failure of the shell plating can be made to occur, under sufficient external pressure, in one of the following three manners: (a) by stresses in the shell reaching the yield strength of the material; (b) by instability or buckling of the shell at stresses below the yield strength of the material; and (c), by what can be considered as a combination of failure by both instability and yield. Assuming constant diameter (d) of the transverse section and adequate but not excessively heavy framing, the relation between the thickness of the shell (t) and the unsupported length between frames (L) will then determine which of the above modes of failure will govern. If the shell is relatively thick and the unsupported length between frames relatively small, the shell will not fail until the material

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is stressed to its yield strength by the combined effect of tangential and longitudinal stresses. The tangential stress resulting from radial compression (i.e., the compressive ''hoop" stress) is the determining influence in this mode of failure. The longitudinal stresses which result from end compression of the cylinder, from flexure of the entire hull as a beam, and from inward bending of the plating between frames under radial hydrostatic pressure, will have only minor influence in bringing about collapse in this case. This type of failure is analogous to the compression failure of a short, thick column. The first manifestation of failure will be the characteristic formation of a series of in and out bulges in the circumferential belt of the shell between frames (See Photo 16-1). However, if the shell is relatively thin and the unsupported length between frames is relatively large, buckling of the shell between frames similar to that just described will occur before the shell has been stressed to the yield strength of the material. In this latter case, the buckling action is called failure by "elastic instability" and collapse will occur at a much lower hydrostatic pressure than in the first case. The action is analogous to the failure by elastic instability of a long slender column. It is of interest to note that in the first type of failure the buckles form after the shell commences to yield plastically, whereas in the second case buckling starts while stresses are still in the elastic range.

16-6. Assuming adequate rigidity, the frames have considerable influence on the strength of the vessel by maintaining the original circular hull form. For a constant shell thickness and diameter, and assuming frame spacing initially of such distance that failure of the hull will occur by elastic instability, then as the frame spacing is decreased (i.e., as the L/D ratio becomes smaller), the collapsing pressure of the vessel will increase, since, although failure will still occur by elastic instability, the "hoop" stresses in the shell when failure occurs will become progressively larger and will approach the yield strength of the material. The collapsing pressure will continue to increase as the frame spacing decreases until the L/D ratio is reduced to that value at which the frames carry a sufficient portion of the load to prevent the shell from buckling until the combination of the "hoop" and longitudinal stresses in the shell material reach the yield strength. The collapsing pressure for the shell then becomes practically independent of further decrease in frame spacing. Once their spacing has been determined, the frames are designed so that they will collapse at a pressure slightly above the pressure that will cause buckling of the shell between the frames.

16-7. A sturdy column is one which will not collapse until stressed to the compressive yield point. The sturdiness of a column depends upon its slenderness ratio (L/r), where (L) is the length of the column and (r) is the least radius of gyration. Generally speaking, the sturdiness increases as the slenderness ratio decreases. Likewise, the sturdiness of a pressure vessel, assuming rigid framing, depends upon

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an analogous slenderness ratio which can be expressed in a manner corresponding to the column theory as below:

When this ratio is modified to include the physical properties of the shell material (S = yield strength, E = modulus of elasticity), it is referred to as the "thinness factor" and is expressed as:

The sturdiness of a pressure vessel increases as the thinness factor decreases. It can be seen that increasing the yield strength of the material, while holding the other factors constant, increases the thinness factor and therefore the prospect that the vessel will fail by elastic instability before the "hoop" stress in the shell due to hydrostatic loading approaches the yield point. If a light, and efficient construction is to be attained, the "hoop" stress in shell material should approach the yield stress before buckling occurs and this requires that a proper balance be achieved between t, L, and D for the yield strength of the steel selected. High strength steels, for example, require relatively close frame spacing if the full yield strength of the material is to be realized.

16-8. Circular submarine hull designs currently in use by the U.S. Navy are considered as thin shell vessels stiffened by rather closely spaced frames that are sufficiently rigid to maintain the circular form until the shell between frames starts to fail. It is intended that the various strength factors be so balanced that when the hydrostatic collapse depth is passed, the hull will commence to fail by buckling of the shell plating between frames at a "hoop" stress close to the yield strength of the steel. This buckling will first occur as a series of in and out bulges or "lobes" distributed around the circumferential belt of the shell between frames, the bulges in adjacent frame spaces being at an angle of approximately 45 degrees to each other.1 Complete failure will follow by rupture of the shell plating at some point of high stress concentration, induced by the plating tearing away from a frame and merging two or more bulges into one large bulge, bending of the frames out of their normal plane or circular shape, or by a tendency of the hull to twist and close up the frame spacing in accordion-like folds due to end pressure. High stress concentrations at hatches, or any type of stress raiser, may very possibly cause a rupture even before the bulge pattern between frames becomes evident.


1 A series of 14 distinct and separate inward bulges (1/2 lobe) should theoretically occur around the complete circumferential belt between each frame space on SS285 Class submarines.

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16-9. In the hope of attaining added safety during attack, and also to better avoid detection, the pressure hull of the SS285 Class was designed to permit a much greater depth of submergence than that of any previous submarines in the U.S. Navy. The increased strength was attained partly by increasing the thickness of the pressure hull plating and partly by use of steel of greater strength, i.e., high tensile steel rather than medium steel. In addition, H-frames were used instead of the I-frames and T-frames employed in previous designs, since H-frames, due to their wider flanges, possess greater torsional and transverse rigidity for a given sectional area and are therefore less susceptible to buckling or upsetting (Photo 16-1)1 It is interesting to note that only two submarines of this Class reported sustaining permanent pressure hull deformation as the result of underwater explosive attack, although many were subjected to close detonations of bombs and depth charges.2 No SS285 Class submarines are known to have sustained any indications of failure due to overdepth.

16-10. Near the forward and after ends of U.S. submarines, the inner circular pressure hull terminates and the outer hull becomes the pressure hull. These single hull ends conform to the lines of the submarine, gradually fairing into a shape which approaches that of an ellipse in cross section. Frames of the single hull portion are internal while those of the cylindrical double hull portion are external to the inner hull. The internal frame, together with a strip of shell acting as a flange, is designed to take the full load, and the shell, except that portion considered as the frame flange, although very heavy and capable of withstanding large loads, is considered primarily as an envelope to keep out the water. The internal frames are designed so that their neutral axis will, as nearly as possible, approximate a circle. The single ends are made slightly stronger than the circular hull to provide some protection against collapse of end structure by reason of trim angle. Past experience and tests have been the guide in progressive development of non-circular hulls rather than theoretical formulae. Several cases have occurred where the single hull ends of U.S. submarines have sustained extensive plating and moderate frame deformation


1 David Taylor Model Basin Conf. Report No. 515 of May 1943 (Hydrostatic Test of a 1/12-Scale Model Pressure-Hull Section of the SS285 Class of Submarines).
2 REDFISH (SS395), depth charged on 19 December 1944 during her second patrol and CREVALLE (SS291), depth charged on 14 May 1944 during her third patrol. See briefs of damage in Appendix I.

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under severe depth charge or bomb attack.1 No serious weaknesses were disclosed in these single hull ends, although areas of plating proved susceptible to local failure. On both TUNNY (SS282) and HALIBUT (SS232), the section of the top pressure hull plating between the forward escape trunk and the forward torpedo loading hatch was markedly depressed, whereas adjacent plating was not affected;2 also on TUNNY, the boss for the bow plane tilting gear in the overhead pressure hull of the forward torpedo room was depressed to a depth of about 2 inches, whereas adjacent plating was not affected;2 on KINGFISH, local depressions occurred in way of the shell plating for engine lubricating oil stowage tank No. 5.3

16-11. Flats bounding tanks exposed to full sea pressure, such as those of the forward and after ballast tanks on SS285 Class and previous submarines where the torpedo room decks form the tank tops, must be capable of withstanding, without excessive de-formation, the maximum pressure corresponding to the collapse depth of the other portions of the vessel. The stiffening for such flats is usually provided by an intersecting system of floors and longitudinals. The plating is divided by these floors and longitudinals into approximately square panels and the welding connecting the flat to the stiffening system makes these members integral components. The design of flats, as in the case of non-circular hulls, is based to a large extent on empirical data derived from tests and service experience. There are three cases known to the Bureau where forward or after ballast tank flats were deformed inward as the result of close bow or stern depth charge or bomb detonations (Photo 16-2).4 In none of these instances was the distortion such that any portion of the plating was torn loose from the stiffening members. In each case, the adjacent single hull plating was also deformed, and to a greater extent than the flats in two of the three cases. It is interesting to note that although TUNNY (SS282) twice sustained extensive shell deformation in her single hull ends, in way of the forward torpedo room in her action of 26 August 1943 (Section VI), and in way of the after torpedo room in her action of 1 September 1944 (Appendix I), in neither case was damage to the torpedo room flats reported.

16-12. The primary function of the main divisional bulkheads on U.S. submarines is to preserve the watertight integrity of the several compartments of the vessel in the event of damage and subsequent flooding from sea. Unlike bulkheads of surface ships, they are neither intended to serve as racking members nor are they primarily designed to support loads on decks above. These bulkheads make no contribution to the collapse strength of the hull and are not intended to take any load


1 TUNNY (SS282), 26 August 1943, Section VI, and HALIBUT (SS232), 14 November 1944, Appendix I, are excellent examples of damage to single hull ends.
2 See paragraph 6-15.
3 See paragraph 5-12.
4 KINGFISH (SS234), 23 March 1943, Section V; HALIBUT (SS232), 14 November 1944, Appendix I; and REDFISH (SS395), 19 December 1944, Appendix I.

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except in the case of flooding or where portions of the bulkheads form the boundaries of pressure tanks. Escapes were enabled from both SQUALUS (SS192) and TANG (SS306) when watertight boundaries which prevented further flooding were established at bulkheads by quick action on the part of the crews. Although in both of these instances the holding bulkheads were not subjected to pressures near the maximum for which they were designed, it is interesting to note that the doors and fittings remained substantially intact under deflection. The bulkhead on SQUALUS showed no signs of permanent set on subsequent examination although it withstood a head of about 230 feet of water for several weeks. One interesting case of bulkhead damage was that which occurred on HALIBUT (SS232) in her action of 14 November 1944, during which the forward portion of her pressure hull received severe damage as the result of close depth charge attacks. The after bulkhead of the forward torpedo room was deflected forward, both port and starboard, but only in that portion at the outer periphery which formed the junction between the inner and outer hulls (Photo 16-3).

16-13. While the factors controlling the strength of submarine hulls to withstand hydrostatic pressure are now well understood, no accepted theory exists as to the strength of a submarine pressure hull under the condition of combined hydrostatic loading and dynamic loading that occurs when a submarine is undergoing attack by explosives at a considerable depth. Experimental data now available is not sufficient to serve as a guide in the formulation of such a theory. However, new and significant information was obtained from the series of deep sea explosive tests conducted on small scale submarine models by the Underwater Explosives Research Laboratory of the Bureau of Ordnance (paragraphs 15-9 and 15-14).

16-14. The modes of failure of submarine structures under combined explosive and hydrostatic loading can be divided into two general classes as follows: (1) immediate splitting or tearing of the pressure hull due to direct action of contact or close detonations; (2) deformation of the pressure hull due to explosive loading, but without splitting or tearing occurring, followed by collapse or tearing due to hydrostatic loading on the weakened structure (if the depth is great enough). The combined effect of hydrostatic loading due to depth, and explosive loading from bomb or depth charge detonations, is greater than either alone, and the lethal distance of a given weight of explosive increases rapidly as the depth of a submarine is increased.1 TANG (SS306), TULLIBEE (SS284), ROBALO (SS273), and FLIER (SS250) are known to have been lost through destruction of a portion of their pressure hulls from close or contact detonations. As stated previously, no U.S. submarines are known to have survived war damage which breached their pressure hulls while submerged. It should be noted that the range at which a given weight of explosive will cause permanent deformation only of a submarine pressure hull is but slightly greater than the range at which the


1 See paragraph 15-14.

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same weight of explosive will cause rupture or complete failure of the hull to occur. The distance increment between the range at which permanent deformation only will occur, and that which will cause complete destruction, considerably decreases as the submergence depth of a submarine increases.

16-15. It is considered that the most serious structural hazard to a submarine from underwater detonations which are located at distances slightly greater than the limiting distance which would in any event cause splitting of the pressure hull, is the possibility of rupture or tearing occurring at a "hard spot" or discontinuity of structure which produces local areas of high stress concentration. There is hardly any portion of a submarine hull structure which is entirely free from these stress raisers, and as a consequence the hulls are vulnerable to failure at such points. Photos 16-4, 16-5 and 16-6 show typical pressure hull failures in areas of stress concentration as obtained during tests conducted by the Bureau on full scale submarine sections at the Navy Yard, Portsmouth, in 1942. The detail specifications for all recent submarines outline methods of attachment of the ends of stiffeners to the strength hulls to insure a measure of protection against dynamic loading from underwater explosions. Liners and pads are provided to protect the hulls against tearing when dented or deflected in the way of the ends of stiffener brackets. Welding is so designed that the stiffeners will pull away from the pads before the pads tear the hull plating. The design details are based on information obtained from many explosion tests, and war experience has shown that the methods are generally satisfactory. An elastic connection is less liable to sustain damage than one that is rigid and forms a hard spot. Hard spots, abrupt changes in area of members, nicks, and unsupported edges of holes are potential starting points of failure and should be avoided. Efforts are made to reduce the locked-in welding stresses both in the design and building of submarines.

16-16. The damage which occurred to SCAMP (SS277) in her action of 7 April 1944 illustrates features of both correct and incorrect detail design. The pressure hull of SCAMP broke free from several frames in way of the heaviest damage (Photo 9-8). This was obviously far less serious than the same damage accompanied by a tear in the hull plating would have been. The frames on SCAMP were I-sections. It is perhaps possible that had H-section frames been installed, as on the SS285 Class, the frames might not have broken free from the hull since inward bending of the wide faying flanges of an H-beam will absorb considerably more energy and deformation than the relatively narrow faying flanges of I-section frames. With either type of frame, however, it is preferable to employ welding of such strength that the frames will break free without tearing the pressure hull. This is insured by the welding design and is facilitated by the fact that the frame welding can only be as heavy as the flange thickness will permit, and, with present frame sections, the maximum strength of such welding is less than that of the shell plating. Undesirable designs for conditions

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of high explosive loading were illustrated by two failures which occurred on SCAMP: (1) tearing of the outer hull tank top plating at frame 79, as detailed in paragraph 9-24 and Photo 9-7; and (2), tearing of the main engine air induction line at its welded bracket supports, as detailed in paragraph 9-22 and Photo 9-5. Both of these failures were caused by high stress concentrations. SCAMP's narrative demonstrates the serious effects such apparently minor design defects may have on the survival of a submarine when attacked.

16-17. The collapse strength of a submarine circular hull is reduced markedly when there is any appreciable departure from a truly circular section. Hydrostatic tests of submarine models demonstrated that those models having even a small degree of out-of-roundness failed at pressures below that required to cause failure of more perfect models. Where the out-of-roundness was limited to a lobe length (see paragraph 16-8) between two adjacent frames, the first bulge to appear as pressure approached the failure value was almost always at this initial buckle or dent, and the bulge patterns spread out from this point. Deep sea explosion tests on SS285 Class pressure hull models conducted by the Underwater Explosives Research Laboratory demonstrated that out-of-roundness was even more detrimental to submarines under combined explosive and hydrostatic loading than under hydrostatic loading alone.1 Current specifications require that at no place shall the maximum radius of the circular hull exceed the minimum radius by more than one-half the shell plating thickness. Tests show that if this tolerance is not exceeded, no appreciable reduction in strength will result. The importance of maintaining the circularity of the pressure hull to within the above tolerance can not be overemphasized. Checks of hull circularity should be made in all cases where submarines have sustained pressure hull deformation.

16-18. Dishing of pressure hull plating between frames due to over-depth operations has occasionally occurred (SALMON Photo 7-5). While it is true that such dishing cannot be considered to have weakened the hull from the standpoint of hydrostatic loading alone, and that the submarine should be able to again safely descend to the depth at which the dishing originally occurred, the resistance of the dished hull to bending stresses and explosive loading is definitely decreased. Once a dish has formed, the plate in the vicinity has absorbed energy which it cannot again absorb and is therefore more susceptible to failure under explosive attack. In all cases where marked pressure hull dishing has occurred, whether due to hydrostatic pressure or explosive attack, the original geometry of the structure should be restored and new plating is recommended.

16-19. Expedients should not be adopted which will in any way weaken submarine hulls or introduce areas of doubtful structural strength. The welding of pressure hull structure back into place falls in the category of restrained welding in which there are always locked-in stresses.


1 OSRD conf. Report No. 5417.

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These stresses may result in the immediate formation of cracks (which for grooved "tee" joints may not be discernible by magna-fluxing or other methods of inspection), or in the failure of the structure under loads considerably below the full strength of the material. Certain alterations and war damage repairs occasionally leave no other course than to cut the hull plating and structure and to install replacement material. Patches, except when worked flush with plating in a cut-out section, are stress raisers, and because of the hard spots introduced are potential danger points even though perfectly welded. The original geometry of the hull should be restored in all cases. Any attachments such as padeyes, cleats, etc. are stress raisers and should be avoided. Even slight nicks, such as those caused by striking a welding arc, will tend to produce notch effects. Experience during the war has demonstrated that the utmost care must be taken on submarine pressure hull repairs and that X-ray or radiographic examinations must be conducted if defects are to be avoided. It is also extremely important to check the physical and chemical properties of the replacement material when any doubt exists as to its meeting the required specifications for the hull area concerned.

16-20. The Bureau has issued rigid instructions on the methods to be employed in cutting and welding of submarine pressure hull structures and structural fittings subject to deep submergence pressure. The reader is invited to refer to the following letters for further information: BuShips conf. ltr. SS/S11-1(515-692) of 8 May 1944; BuShips conf. ltr. SS/S29-6(515) of 15 May 1944; and BuShips conf. ltr. SS/S11-1(515) of 2 April 1945.

16-21. The marked improvement of welded construction over riveted construction in resistance to war damage has been repeatedly demonstrated in both surface vessels and submarines. There is no reported instance where welds in U.S. submarine pressure hulls have failed as the result of war damage. This fact of course does not preclude the possibility of such failures having occurred, since the results would very likely have proven fatal to the submarine concerned. That welding has proved so satisfactory on our submarines is attributable to the constant emphasis placed by the U.S. Navy on improving welding methods and materials, adequate training of welders, qualified supervision, frequent inspection, and the correct design of ship welding details. Experience has demonstrated the importance of proper welding sequence in the control of shrinkage, distortion, locked-in stresses and cracking during construction. The importance of good workmanship cannot be overemphasized. Poor workmanship engenders fracture, since failure may originate at a small notch such as is occasioned by peened-over cracks, undercut welds, porosity and inclusions in the weld, improper joint preparation resulting in incomplete penetration which leaves voids at the center of the joint, incomplete backside root chipping on grooved joints, etc. The importance of maintaining the welding standards set forth by the Bureau for production and repair welds for submarine pressure hulls cannot be overemphasized.

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16-22. It is interesting to note that there are several submarines which have been quite heavily depth charged and on which laminated pressure hull plates were subsequently found. In theory, laminated plates involve a loss in strength. However, this assumes the lamination to be complete; that is, that there is a free plane of cleavage which would permit the separated plates to move freely relative to each other. In practice, the laminations are not free planes but are irregular and partially fused surfaces. It is believed that such surfaces will act in shear substantially as if joined and that no important loss in strength will result. When encountered, they should not be regarded as cause for alarm. Nevertheless, laminated plates should never be worked into submarine structure, and when found during construction or repair should be removed if possible.1

16-23. War experience indicates that riveted and bolted access plates as fitted in submarine pressure hulls have been generally satisfactory in strength compared with other portions of the pressure hull, but that when extreme shell deformation occurs, the joints of such plates tend to open and may develop serious leakage. For example, on GRENADIER (SS210)2 during the action leading to her loss on 22 April 1943, the riveted plate over the maneuvering room tore partially free from adjacent plating when the pressure hull in that area was damaged. This allowed a stream of sea water to cascade upon the main control cubicle beneath and was one of the factors which caused loss of propulsion. Riveted plates, however, appear to withstand moderate deformation without tearing or developing excessive leakage. On both SALMON (SS182) and KINGFISH (SS234), the riveted plates in way of the areas of pressure hull damage were themselves considerably deformed but remained tight or nearly so.3 However, on KINGFISH, several riveted keystone frame joints started to separate (Photo 5-2).

16-24. Riveted and bolted plates, when properly designed and fitted, are not structurally weak from the standpoint of normal hydrostatic loading. However, double butt-straps act to create hard spots and thus may weaken adjoining structure rather than in themselves constituting a weakness, and riveted construction is not fundamentally desirable from the standpoint of watertightness when subjected to large deformations. In addition, the reinstallation of riveted plates, once removed, usually involves considerable time and expense. New butt-straps and plates are frequently required; oversize holes must be welded


1 BuShips ltr. SS283/S11(515) of 4 November 1944.
2 See GRENADIER narrative, Section VIII.
3 See KINGFISH narrative, Section V, and SALMON narrative, Section VII.

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up and redrilled; caulking edges may have to be built up by welding; faying surfaces on adjacent pressure hull structure occasionally develop ripples; obtaining metal to metal contact along the longitudinal seams is often a long and arduous process; and reriveting may be substandard. It now appears possible that the use of riveted portable plates may be discontinued in favor of welded plates on both new construction and submarines in service. However, it is intended that bolted access plates will be retained in those locations where repeated removal may be necessary, such as for battery and parts replacement.

16-25. The rupture of the forward torpedo room 37.5 pound HTS pressure hull plating on DRAGONET, as the result of striking a rocky promontory while submerged, is an excellent example of the type of failure to be expected when heavy concentrated loading is applied to restrained plating panels. In DRAGONET's case, it is quite likely that the force of grounding was sufficient to cause the shell to fracture in any event. This is indicated by the fact that one of the frames supporting the plating also broke. However, the plating was greatly restrained in the area of rupture by extremely strong and rigid internal frames, spaced on 24 inch centers, which acted to prevent vertical movement and tended to increase the likelihood of early fracture. The capacity of restrained material to absorb energy is reduced markedly since the ability of the material to flow plastically is less than that of unrestrained plating. The fact that DRAGONET was operating in water at a temperature about 29°F.1 may have been a contributing factor in the failure of the pressure hull plating. It has been definitely established that low temperature greatly reduces the ability of both MS and HTS to absorb energy. The temperature below which the capacity of steel to absorb energy decreases rapidly is generally referred to as the transition temperature. Below the transition temperature, fractures show a brittle, crystalline surface in contrast to the fibrous type associated with the same steel at higher temperatures. The few test results available seem to show only a negligible change in yield strength as the temperature is lowered. Therefore, under static or slowly applied loads, it is not considered that appreciable change in strength is to be expected. Temperature effects are reflected in impact and notch tests rather than in static tests. Since the transition temperature has been found by actual tests to vary from -20°F. to well over 100°F. with different samples of MS and HTS, although all of the samples satisfied the specifications, it is impossible without actually testing the material in the region of the failure on DRAGONET to determine its transition temperature. The appearance of the fractures on DRAGONET suggests that low temperature may have been a factor in the plating failure, although as previously stated, the force of grounding was no doubt sufficient to have caused the failure. It should be noted that the average transition temperature of high tensile steels, as in the pressure hulls of SS285 Class and subsequent submarines, (less SS361-364), is considerably lower than the average for the


1 Temperature measured at engine injection (saltwater).

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medium steels used in previous submarine classes, and therefore the use of HTS material can be considered as a definite improvement over MS in this respect.

16-26. Ballistic protection on U.S. submarines has been limited to the installation of 20 and 30 pound STS for the protection of bridge personnel and 40 pound STS for ready service ammunition. In addition on SS285 Class submarines the entire conning towers, including the ellipsoidal end bulkheads, were fabricated from 40 pound STS for this purpose. Ballistic protection was authorized in April 1943 for all fleet type submarines subsequent to SS197 when the need for shielding the vulnerable bridge, conning tower and ready service ammunition was demonstrated by several aircraft strafing and small caliber surface engagements, such as GROWLER's action of 7 February 1943.1 Generally speaking, and disregarding a possible high velocity of approach of the firing weapon, 20 pound STS will provide protection against normal impact of .50 caliber projectiles fired from a range of 1000 yards and 40 pound STS will provide similar protection at 100 yards. In at least two instances the STS plating on our submarines was penetrated.2 With the exception of the conning tower hatch on GROWLER, there were no instances where either conning towers or pressure hulls were penetrated by small caliber enemy projectiles. This is attributable to the low incidence of such attacks rather than to the meager protection afforded by the small amount of STS plating provided for our submarines. The design problem in ballistic protection of submarines is one of calculated risk in any event since weight and stability considerations will not permit extensive use of STS in thicknesses sufficient to insure defeat of small caliber projectiles fired at close range.

16-27. The structural design of modern submarines is the result of evolution over a period of many years. Research, particularly with full scale caissons, initiated by the Bureau and accomplished mainly at Portsmouth, N.H., and model tests and theoretical analyses by the David Taylor Model Basin have contributed greatly to present knowledge and design practices. While marked advances have been achieved in the past several years, further improvements appear definitely possible. The elimination, where possible, of hard spots and potential points of stress concentration in pressure hulls is a matter which should be borne in mind by the operating personnel in establishing requirements and features which require pressure hull penetration. Hull openings should be held to an absolute minimum. Theoretical investigations and further controlled testing of models and full scale vessels are required to widen the field of knowledge on the behavior of submarines under explosive attack. Steels are currently under development which it is hoped will combine the desirable qualities of high yield strength; high ductility; notch toughness; increased energy absorption characteristics at the high strain rate conditions which result from explosive loading; weldability; and low transition temperatures. Submarine hull designs for operation at depths of as much as 1000 feet may then become feasible within the percentage of submarine total weight which can be devoted to hull structure.


1 See GROWLER narrative, Section XIII.
2 See briefs of damage in Appendix I for SKATE (SS305), 6 October 1943; and POGY (SS266), 19 April 1945.

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Photo 16-1: View of Model No. 107 after hydrostatic test at U.S. Navy Experimental Model Basin. Note typical example of bulge formation in shell and failure of frame having insufficient rigidity. The need for wider frame flanges is clearly indicated, such as provided in the H-frame sections used on SS285 Class submarines.

Photo 16-2: HALIBUT (SS232). View showing deformation which occurred to MBT No. 1 tank top flat in forward torpedo room of HALIBUT (SS232) as a result of her action of 14 November 1944. Washboard effect on port side is shown.

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Photo 16-3: HALIBUT (SS232). View showing buckled area of after bulkhead of forward torpedo room on HALIBUT (SS232) as a result of her action of 14 November 1944. Bulkhead was deflected forward in peripheral strip between the junction of the inner and outer hulls, from about 40° below top center to about 90° from top center, both port and starboard.

Photo 16-4: Typical example of tearing of inner shell at stress concentration formed by incorrect junction of bulkhead stiffener as obtained by explosive tests on a full scale submarine partial length section at the Navy Yard, Portsmouth in 1942.

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Photos 16-5 and 16-6. Typical failures of inner hull as obtained by explosive tests on a full scale submarine partial length section at the Navy Yard, Portsmouth in 1942. Above: tear in pressure hull plating at tank top margin plate. Note that I-frames are torn from pressure hull. Below: tear in pressure hull at junction of I-frame with tank top margin plate.

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SECTION XVII

STABILITY, BUOYANCY AND FLOODING

17-1. The stability, buoyancy and trim of a submarine present a unique problem, involving three main phases: (1) operation as a surface vessel, (2) the period of submergence or surfacing and (3) underwater operation. While operating on the surface, the stability and trim of a submarine and calculations thereof are the same as for an ordinary surface ship. The calculation of stability for the submerging period is based on the same principles as for the surfaced condition but is considerably more complicated since arbitrary assumptions must be made as to the rate of flooding of various tanks, the angle of trim while the boat is diving, etc. Calculation of stability in the fully submerged condition is a very simple matter since both the transverse and longitudinal metacenters move to the center of buoyancy. The metacentric height or GM, uncorrected for free surface, is then measured both transversely and longitudinally by the vertical distance between the center of gravity and center of buoyancy. Balance calculations for weight and buoyancy changes in the submerged condition involve only weight and moment computations and are familiar to all submarine officers.

17-2. War experience has repeatedly demonstrated that changes in stability and weight and buoyancy distribution on submarines will frequently be caused as a direct or indirect consequence of damage and that where such changes are relatively large, ship control submerged may be lost or excessive list and trim angles may result on surfacing. In several instances our submarines have been subjected to serious military hazard following damage sustained while submerged due to inability to retain depth control, forcing bottoming or surfacing, and in at least one instance an excessive list assumed by a U.S. submarine upon surfacing after damage would probably have caused her loss had the enemy been more alert (paragraph 17-4).

17-3. DRAGONET, SALMON and SCAMP are among those submarines which assumed large lists upon surfacing after receiving damage.1 In each of these instances, the lists were caused by unsymmetrical liquid loading in external tanks. DRAGONET was reported to have assumed approximately 15 degrees port list due to inability to expel water more than a few feet below the tops of two ruptured port main ballast tanks, a fact unknown to her at the time the remainder of the ballast tanks were blown dry on surfacing. In DRAGONET's case, the list caused by the heeling moment of the two partially flooded port tanks was also slightly aggravated by the free surface effect of the water in the flooded forward torpedo room. However, calculations indicate that the reduction in metacentric height resulting from the free surface and added weight of the water in the forward torpedo room, considering the water level to have been approximately two feet above the forward torpedo room flat, was only about 0.18 foot. This was a minor reduction compared with


1 See Sections VII, IX and XIV for narratives of SALMON, SCAMP and DRAGONET.

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DRAGONET's total probable GM before damage of about 1.50 feet,1 and caused the list to increase by only about one degree. Calculations also indicate that the list was probably of the order of 10 degrees rather than the reported 15 degrees. SCAMP assumed about 17 degrees port list upon surfacing, due to inability to expel water from two port main ballast tanks and the displacement of fuel oil in one port fuel ballast tank with heavier sea water through a rupture in the tank top plating. SALMON assumed about 15 degrees starboard list on first surfacing, due to leaking starboard ballast tank master vent valves and the displacement of fuel oil in one starboard fuel ballast tank with sea water through a damaged riser. In both of these latter cases, the lists were no doubt increased to a minor extent by loss of GM due to the free surface effect of the sea water which accumulated in internal compartments from various sources' of leakage.

17-4. It should generally be expected that a submarine which sustains damage to external tanks, risers, master vent valves or the low pressure blow system to individual tanks will almost invariably assume a large list upon first surfacing. This will occur primarily because the extent and nature of such external damage will not be known while still submerged and will manifest itself only when the ship actually does list upon breaking the surface or after following normal tank blowing procedure. Large lists assumed upon surfacing should not normally be dangerous since rapid compensation can of course be made either by venting ballast tanks on the high side or by selective blowing of ballast tanks on the low side. It has been demonstrated on several occasions that submarines can quickly get underway on their surface Diesel propulsion plants even with lists as high as 15 degrees. SCAMP and DRAGONET are two such examples However, should a large list persist on a submarine after surfacing, and if the submarine were unable to resubmerge if attacked during this period, due to damage, low air reservoirs or depleted batteries, gun operations and ship handling would certainly be hampered, if not impossible. For example, SALMON would very probably have been destroyed after surfacing in her action of 30 October 1944 had the enemy escorts not delayed their attack until the ship's force had taken damage control measures and successfully righted the boat.

17-5. Calculations made for SS285 Class submarines show that a boat which is initially in normal diving trim will assume a 45 degree list if all main ballast and fuel ballast tanks on one side only are completely flooded to the tank tops while the corresponding tanks on the opposite side remain dry. This might be considered to represent the maximum possible listing moment for a surfaced submarine. Calculations have also been made to determine what angle of heel might result in the hypothetical case occurring if all main ballast tanks on one side only (not including fuel ballast tanks) were blown completely dry while submerged. The boat would then surface rapidly, of course, and while rising would steady at a list of about 70 degrees, assuming the boat rises through a sufficient distance for equilibrium conditions to occur before surfacing. On surfacing, the list would be sharply reduced to about 33 degrees since the introduction of water plane area greatly increases the


1 Condition VII-B, Emergency Diving Trim, Revised Inclining Experiment Data for DRAGONET.

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metacentric height (note that in this case only 33 degrees list results after surfacing rather than the 45 degrees calculated for the case above, since the fuel ballast tanks on both sides are considered to remain flooded).

17-6. The freeboard and reserve buoyancy of U.S. submarines now in service are sufficient even in emergency diving trim condition to permit several main ballast tanks to remain free flooding for list control, when necessary. However, if a large number of ballast tank master vent valves or risers are damaged, a submarine may then experience difficulty after surfacing in blowing up far enough to achieve satisfactory seaworthiness. For example, SALMON remained just barely awash for several minutes after surfacing due to loss of tank air through leaking master vent valves and was not able to blow up until the emergency vent valves were closed. This delay, in addition to her large list, hampered damage control efforts and gun operations.

17-7. While returning to base with her forward torpedo room partially flooded, DRAGONET reported reaching a roll of 63 degrees from upright to one side as measured by the control room inclinometer.1 At the time this occurred, heavy quartering seas and winds of gale force were being encountered. There are many other similar cases on record where submarines have reported extreme rolls. For example, SNAPPER (SS185) on her eighth war patrol and SEADRAGON (SS194) on her shakedown cruise after commissioning reported rolls reaching 45 degrees or more at times. Also, while operating off Newfoundland on 17 November 1946, DOGFISH (SS350) and SABLEFISH (SS303) reported maximum rolls from upright to one side of 52 degrees and 63 degrees, respectively, and average rolls from upright to one side of 35 degrees and 20 degrees, respectively. In all of these five cases the rolls were measured by inclinometer. It should be noted that this type of instrument is not accurate for recording large angles of roll and will in such cases indicate somewhat greater angles than actually occur. The circumstances attendant at the time the extreme rolls occurred were quite similar in each case: high wind velocities and heavy quartering seas. The periods of roll were long and the vessels seemed to "hang" at the end of the large angle rolls before returning to upright. In three of the five cases, water was shipped through the outboard induction valves and conning tower hatches. SABLEFISH reported that on her 63 degree roll it was necessary to blow ballast tanks on the low side with high pressure air in order to right the ship. DRAGONET reported that on her 63 degree roll it was necessary to swing the ship's heading through 105 degrees before the vessel slowly commenced to right herself and then steadied at about 20 degrees list. With the exception of DRAGONET, all of the above vessels are believed to have been in emergency diving trim condition.

17-8. As nearly as can be determined, SNAPPER and SEADRAGON each had a GM of approximately 1.00 foot and DRAGONET, DOGFISH and SABLEFISH each had a GM of 1.25 feet or larger. As mentioned previously, the loss in stability on DRAGONET due to the flooded forward torpedo room was minor, having the effect of reducing her GM from about


1 See paragraph 14-18.

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1.50 feet to 1.32 feet. These values of GM are more than sufficient to assure a range of stability considerably beyond 90 degrees and it is difficult to explain the tendency of the submarines cited above to "hang" at extreme angles. This "hanging" behavior is similar to that which is often reported by destroyers and minesweepers, or occasionally even larger surface vessels, under identical conditions, i.e., heavy quartering seas. The extreme rolls evidently occur as the vessels roll away from the crests of waves which are momentarily in synchronism. All vessels are subject to this action in a seaway under the right conditions. The extreme example is the broaching of landing craft in a surf. The smaller the vessel, the larger the part that must be played by seamanship to avert disaster. On a submarine, the tendency to "hang" under certain wave and wind conditions is probably aggravated by the fact that the tank tops and part of the superstructure deck will be submerged at large angles of roll, these surfaces tending to act as a plane to hold the submarine at the extreme angle of roll while it is displaced sideways due to the dynamic action of the waves.

17-9. Another factor which may contribute to the tendency to "hang" is that at large angles of roll it is possible for a submarine to spill air from ballast tanks on the low side and take on water through the flood openings, with resultant increase in heeling moment. A study made in 1942, taking into account the loss of air and consequently the partial flooding of low side main ballast tanks, indicated that statically the effect on stability was maximum between 50 degrees and 60 degrees of heel but was only a minor consideration, the loss of righting arm being less than 0.10 feet. This study also indicated that the statical stability improved beyond 60 or 70 degrees due to the addition of low weight by partial flooding of the low side tanks. The additional heeling effect of such weight would be large, of course, and tank blowing may be required in order to again right the ship. Tank blowing will only partially remove the water in the low tanks at extreme angles but should have some beneficial effect and is probably the correct course of action to take when such a case is believed to exist. It should also be noted that when air spillage occurs from low side tanks, the submarine upon righting itself will not return to the vertical but will assume a list in the direction of the low side tanks, due to the added water in those tanks, and tank blowing will then become necessary to reach the fully upright condition. Whether "hanging" at an excessive angle is due only to the synchronism of dynamic wind and sea forces, or whether progressive loss of tank air with increasing roll angle contributes appreciably to the "hanging" tendency, is not clear at present. Rolling, heaving and pitching, accompanied by heavy seas, will result in variation in head over the tank flood openings and will tend to cause loss of tank air, allowing partial flooding which will in turn reduce stability due to increased free surface effects.

17-10. Although submarines have a very poor hull form for surface transverse dynamic stability, nearly circular in cross section with very little freeboard and extreme tumblehome, the possibility of capsizing

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through loss of stability is remote. They have a positive righting moment over a wider range than most ships due to a lower center of gravity and have a smaller area exposed to the force of the wind. Submarines now in service have a range of stability beyond 90 degrees and, in addition, the hull is kept more completely closed in normal operation than in other types of vessels, the conning tower hatch and engine air induction outboard valve being the only openings. The criterion of surface stability in current use for modern fleet type submarines is that the GM in normal diving trim condition shall not be less than 1.25 feet. This figure was decided upon as a result of Bureau studies of wind heeling moments combined with synchronous rolling, and the curves of righting moments of fleet type submarines. It results in righting arms throughout the range of stability which provide a considerable margin of safety over those of SNAPPER at the time of her reported heavy rolling.

17-11. When submerging or surfacing, submarines pass through a period of low metacentric height. This condition occurs when the moment of inertia of the reduced waterplane reaches a low value concurrently with free surface effects due to partially filled ballast tanks. In modern double-hull submarines, this point of minimum GM occurs when the ballast tanks are about 70 to 80 per cent full. The detail specifications for these vessels require a minimum GM of 3 inches when submerging or surfacing. However, even with slightly negative GM when trimming down, the righting moment soon becomes positive as angle of heel increases and no real danger exists for the vessel. In addition, the condition of minimum stability is transitory, existing for probably less than a second during a normal dive.

17-12. Damaged stability and flooding studies have been made for submarines as for other combatant vessels. The amount of flooding a submarine can sustain and still operate submerged is limited at most to the relatively small capacity of the variable ballast, safety and negative tanks plus a small additional amount which can be compensated for by use of the diving planes and angles on the boat at high submerged speeds. Usually the amount of flooding which can occur while submerged without causing loss of depth control will be much less than the capacity of the above tanks since any longitudinal moments introduced by the flooding must also be balanced by the use of the same tanks, assuming that diving planes and angles on the boat are not used for moment compensation. For surface conditions, however, a submarine can absorb a considerable amount of flooding of internal compartments and tanks before upending or capsizing of the vessel will occur, particularly when the flooding occurs in amidships compartments and the submarine is in normal rather than emergency diving trim, i.e. when the fuel ballast tanks are empty.

17-13. The table below presents several hypothetical cases of flooding for SS285 Class submarines and the resulting effects

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on transverse stability and longitudinal trim when surfaced. The calculations were made for both the normal and emergency diving trim conditions. The submarine is considered to upend when the longitudinal moment tending to trim the ship after flooding remains greater than the opposing longitudinal moment of buoyancy until a near vertical position is reached. The initial transverse GM in normal diving trim was taken as 1.63 feet and in emergency diving trim as 1.59 feet, both figures being considerably greater than corresponding values for SS285 Class submarines now in service. Therefore, the figures given for lists resulting from off-center flooding are somewhat lower than would actually be the case for SS285 Class submarines in service.

Spaces Flooded
(to new water line)

Normal Diving Trim

Emergency2 Diving Trim

Trim on Boat
After Flooding
Occurs

Loss in
Transv.
GM

Trim on Boat
After Flooding
Occurs

Loss in
Transv.
GM

Forward Torpedo Room

4'- 4" By Bow

0.43'

6'-11'' By Bow

0.61'

Forward Torpedo Room and MBT No. 1

7'-11" By Bow

0.17'

Ship upends

- -

Forward Torpedo Room and For'd Battery Comp't.

Ship upends

- -

Ship upends

- -

For'd Battery Comp't.
Control Room
MBT No. 2A

6'-8" By Bow
(List-5.3° Stbd)

0.38'

Ship upends

- -

Control RoomAfter Battery Comp't.
FBT No. 3A

2'-7" By Bow
(List-7.7° Stbd)

0.59'

Ship upends

- -

After Battery Comp't. For'd Engine Room
FBT No. 5A1

1'-9" By Stern
(List-9.5° Stbd)

0.77'

1'-7'' By Stern
(List 3.6° Stbd)1

1.26'

For'd Engine Room
After Engine Room
MBT No. 6C

5'-8" By Stern
(List-12.6° Stbd)

1.04'

Ship upends

- -

After Engine Room
Maneuvering Room

7'-1" By Stern

1.01'

Ship upends

- -

After Torpedo Room

4'-3" By Stern

0.56'

4'-9" By Stern

0.78'

After Torpedo Room
MBT No. 7

6'-6" By Stem

0.77'

9'-0" By Stern

0.77'


1 Assuming FBT No. 5A full of sea water and FBT No. 5B full of oil.
2 Now called Maximum Diving Trim

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The above table emphasizes the marked increase in ability of a surfaced submarine to absorb flooding when in normal diving trim as compared with emergency diving trim, due to the additional freeboard and reserve buoyancy of the lighter load condition. The extreme susceptibility of a damaged submarine to upend through reduction of longitudinal stability should also be noted. A submarine will usually be lost by upending, rather than by capsizing or bodily sinkage. These studies indicate that recent types of submarines, while surfaced and in emergency diving trim, i.e., in usual wartime surface condition, can probably survive the flooding of one major compartment and adjacent tanks with the possible exception of flooding of the forward torpedo room. In the latter case, blowing the bow buoyancy tank, if such remains possible after damage, should assure that upending will not result.

17-14. Also to be considered as a possible damaged condition is the flooding of the conning tower while submerged combined with the damage control measure of blowing the safety tank to maintain neutral buoyancy submerged. For modern submarines, the loss of GM will be only about 0.13 feet when submerged, and 0.18 feet after surfacing. In either case, this slight decrease in GM will not have a serious effect on the ship. It should be noted that the capacity of the safety tank is purposely designed to be slightly greater than that of the conning tower so that it can provide a rapid means of compensating for a flooded conning tower.

17-15. The longitudinal GM of a completely submerged submarine is very small as compared to the surfaced condition, being essentially equal to, or, considering free surface effect, slightly less than the transverse GM, both being a function of the distance between the center of gravity and the center of buoyancy. Consequently, relatively small changes in longitudinal moment will have relatively large effect on trim and therefore on the ability to maintain satisfactory ship control when submerged. In addition, changes in total weight will place a submarine in a condition of either positive or negative buoyancy and will affect depth control. When considering the ability of submerged submarines to sustain war damage, it is apparent that this sensitivity to small changes in moment and weight constitutes one of their most vulnerable aspects.

17-16. The flooding of a submarine major compartment when submerged is a serious matter. If the damaged compartment is at either end of a submarine, and if flooding is rapid, blowing of all ballast tanks to surface would probably result in serious loss of air and in upending. Under such conditions the pressure in the tanks at the high end is less than in the low end and the blowing would therefore unwater the tankage at the high end first and increase the trim angle to such an extent that the air would be spilled out of the flood openings and blowing would become comparatively ineffective. It would be far better to first blow the tankage at the low end and decrease the trim angle before unwatering the tankage at the other end. In the case of SQUALUS, it is believed that had only the after tanks been blown at first, the ship might have been surfaced.

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If a submarine settles on the bottom after flooding a major compartment, and assuming the bottom at a depth less than the designed collapse depth of the hull or of the watertight compartment bulkhead, various methods of self-salvage may be attempted. The first and most logical method is, of course, to dewater the flooded compartment by use of the internal salvage air system, as was successfully accomplished in DRAGONET's case.1 If, for some reason, dewatering of the flooded compartment is not feasible, then it is still possible to surface the submarine, without upending, by calculating moments and blowing only those tanks which will provide both a slight margin of reserve buoyancy and an overall longitudinal moment balance such that reasonable trim control can be maintained while rising, either by use of propulsion and the diving planes or by such means as shifting men and pumping, blowing or flooding forward and after variable tanks. In the case of a flooded end compartment, or where more than one compartment is flooded, normal fuel oil tanks should be considered for blowing as well as main ballast, fuel ballast and variable tanks. Blowing should progress from the damaged end. After surfacing, certain additional tanks may then be safely blown to provide additional freeboard and reserve buoyancy since the longitudinal GM will increase tremendously when water plane area is once established.

17-17. An interesting example of flooding in amidships compartments is the experience of CREVALLE (SS291) during her fifth war patrol. On 11 September 1944 CREVALLE surfaced with her ballast tank vents unintentionally still open and the bridge was manned. Fifteen seconds later the ship took a large down angle and resubmerged with the upper and lower conning tower hatches still open. The ship was making standard speed on battery propulsion at this time and as she submerged the ahead motion accelerated her descent and the down angle increased rapidly. Water poured into the conning tower and thence to the control room and pump room. The forward and after bulkhead doors of the control room were quickly closed and prevented flooding forward and aft. At 150 feet the upper hatch seated but by this time the water in the conning tower had reached armpit depth, the pump room was completely flooded and the control room was flooded above the door to the forward battery compartment (at the large down angle). At about this time, full speed astern was ordered by a quick thinking MoMM 1/c who had tried in vain to contact the control room and conning tower and then telephoned the maneuvering room. With propulsion reversed, descent was checked at 190 feet with a down angle of about 42 degrees. The ship then surfaced, backing full all the way. Since all electrical equipment in the conning tower, control room and pump room was grounded out, CREVALLE was forced

17-18. In over twenty-five instances during World War II, U.S. submarines suffered marked loss of ability to retain depth control after sustaining damage from enemy action while operating submerged. In most of these cases, loss of control was only temporary and had no serious consequences. In several instances, however, loss of depth


1 See Section XIV for DRAGONET narrative.

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control was prolonged or permanent and resulted in oscillations over a wide range of depths, broaching, bottoming, or forced early surfacing with consequent increase in hazard.

17-19. Derangements which prevented use of either or both the bow and stern planes for short periods of time were responsible for most of the cases of temporary loss of depth control, although added weight due to relatively minor flooding was sometimes an additional or the sole factor involved. The instances in which serious or prolonged loss of depth control was experienced were for the most part caused by the additive effect of several of the following factors: flooding of engine air induction and ship's supply ventilation systems; flooding of sanitary, trim and auxiliary tanks; relatively large intake of water into one or more compartments through various sources of leakage; loss of propulsion power; temporary or permanent derangement of bow and stern planes; and displacement of fuel oil with heavier sea water in damaged external fuel tanks. The suddenness with which damage occurred was often a contributory cause of loss of depth control. For example, rapid flooding of an induction system or sudden disabling of diving planes when set on large rise or dive angles frequently resulted in a boat assuming a considerable angle or large change in depth before corrective measures could be taken. In such cases restoration of control therefore became more difficult. The outflow of water ahead of the expanding gas bubbles of close underwater detonations in some cases also forced submarines to assume large angles of inclination or changes in depth (See paragraph 15-8).

17-20. The following instances of loss of depth control are particularly interesting and serve to illustrate typical situations which submarine officers may expect to occur following war damage: KINGFISH (SS234), Section V; TUNNY (SS282), Section VI; SALMON (SS182), Section VII; SCAMP (SS277), Section DC; SARGO (SS188), 4 March 1942, Appendix I; JACK (SS259), 26 June 1943, Appendix I; GURNARD (SS254), 6 July 1943, Appendix I; ALBACORE (SS218), 10 November 1943, Appendix I; TINOSA (SS283), 22 November 1943, Appendix I; BLUEGILL (SS242), 22 May 1944, Appendix I; SAILFISH (SS192), 4 November 1944, Appendix I; and HAWKBILL (SS366), 18 July 1945, Appendix I. The methods which were employed to regain depth control varied with the circumstances of each case. Weight compensation by flooding, venting, pumping or blowing variable, safety and negative tanks was resorted to whenever the tactical situation permitted. With extreme weight and trim changes, submarines were forced to blow ballast tanks or back with both propulsion shafts in order to check downward descent. After becoming heavy overall as a result of damage, several submarines managed to retain fairly satisfactory depth control by resorting to fast speeds ahead at large up angles. Two such examples are the experiences of SCULPIN (SS191) on 28 September 1942 and WHALE (SS239) on 30 October 1942, briefs of these actions being contained in Appendix I. It should be noted that once a submarine becomes heavy and has to use pumps, air or high speed to maintain depth control, the resulting noise increases the possibility of detection by enemy vessels using sonic listening gear.

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17-21. The maximum extent of flooding which a submarine can sustain and still operate submerged depends on the ships ballasting, condition of loading, location of flooding and ability to maintain depth control by use of planes, "bubbles" in tanks, and angles on the boat at high speeds. Flooding introduces added weight plus a trimming moment, both of which must be counteracted if depth control is to be retained. Weights added in amidships areas are obviously easier to compensate with the means available than weights added either forward or aft since the safety tank, which is amidships, can be blown, the resultant of the lift forces obtained by putting an up angle on a submarine at ahead speeds is exerted amidships, and the trimming moment introduced by an amidships weight is much less than an equivalent weight added forward or aft. Calculations based on SS475 Class model tests indicate that an added weight amidships of at least 50,000 pounds can be compensated by proceeding at an ahead speed of six knots with an up angle of 20 degrees on the boat.1

17-22. Several interesting tests were made on ENTEMEDOR (SS340) during April 1946 to determine how quickly the descent or rise of a heavy or light submarine could be stopped when not under propulsion.2 The submarine was first balanced dead in the water. Then, with the boat about 5000 pounds light or heavy, and allowing sufficient time for the limiting velocity of rise or descent to be reached, it was found that in every case the vertical motion could be stopped in from 10 to 20 feet of travel by cancelling the 5000-pound force and adding 5000 pounds in the direction opposite to the motion. A test was also conducted during this same period to determine the hull angle required on ENTEMEDOR to counteract the effect of the bow planes at various angles so that depth control could be maintained with the stern planes alone. At speed 6.4 knots and with neutral buoyancy, it was found that if the bow planes were locked on 25 degrees rise angle, a 5 degree down angle was required on the boat to maintain constant depth. With the bow planes locked at 25 degrees dive angle, a 2.5 degree up angle on the hull was required. Since there are many war damage cases where bow planes have been temporarily or permanently disabled, such as occurred on TUNNY (Section VI), it is interesting to note that even with the bow planes locked on hard rise or dive angles the effect on depth control is not serious provided the stern planes and propulsion remain available.

17-23. As the safety tank is a pressure tank located near the center of balance and has a capacity of about 20 tons which can be quickly blown with high pressure air, it is ideally suited for rapid compensation of a submarine which suddenly becomes heavy overall due to damage. Upon recommendation by ComSubPac in May 1943, the installation of liquidometer gauges in the safety tank of all fleet type submarines was authorized to permit finer control when necessary to blow the safety tank partially and quickly, and to afford a means of avoiding the release of an air bubble through over-blowing if ever necessary to blow the safety dry during evasion maneuvers.3 The inboard vent lines from this tank were also cross-connected and led into the control room to permit operation at that location.4


1 Experimental Towing Tank conf. Report No. 309 of December 1946, prepared by the Stevens Institute of Technology (Hydrodynamic Coefficients of a Self-Propelled Model of the SS475 Class Submarine).
2 Preliminary Report entitled "Performance Characteristics of Submerged Submarines, Tests on U.S.S. ENTEMEDOR (SS340)", dated 23 April 1946, prepared by The Woods Hole Oceanographic Institution.
3 ShipAlt SS206 of 5 December 1943.
4 BuShips ltr. SS/S48-23(515) of 13 August 1943.

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SECTION XVIII

SHOCK PROTECTION

18-1. The vulnerability of a submarine to damage from underwater non-contact explosions depends upon the shock resistance of its vital equipment and fittings at least as much as on the dynamic strength of its pressure hull. From the standpoint of vulnerability to underwater explosive attack, the ideal submarine can be considered as one with a hull having maximum damage-resistance for the weight of material devoted to it, and with all other equipment, appurtenances, systems, etc., of such strength or so well protected from shock that the pressure hull itself will be critically damaged before other vital components sustain serious damage.

18-2. The term "shock" implies a transient or sudden and violent change in the state of motion of the component parts or particles of a body or medium, resulting from the sudden application of a relatively large external force, such as a blow or impact.1 There are two distinguishing characteristics associated with shock motion: (1) the time duration of the motion is limited, and (2) generally the motion is non-periodic, that is, it does not repeat itself at regular intervals of time, as does, for example, a sustained steady-state motion such as a "forced vibration".

18-3. An object will acquire shock motion upon the application of a sufficiently intense force system whose characteristics vary with time. The nature of the motion will be determined by the nature of the applied force system and by the characteristics of the object, principally its mass distribution and elasticity. Shock motions may vary widely in character and type. The initiating force systems which produce shock motion on submarines when subjected to underwater explosive attack are the pressure wave or waves created in the water by the explosives (see Figure 15-1). It is fairly well established that, except for damage caused by the subsequent "whipping" of the hull, shock damage from underwater non-contact explosions is due almost entirely to the initial steep-fronted pressure wave created at the instant of detonation. Contrary to what might be expected, the most serious and extensive cases of shock damage to surface naval vessels have been the result of non-contact underwater explosions rather than contact explosions, probably because water is a more effective transmission agent than the structure of a vessel for distributing the shock throughout the vessel. In submarines, only the problem of non-contact explosions need be considered since contact explosions would invariably cause lethal damage by rupture of the pressure hull and, in any event, the magnitude of shock damage resulting from non-contact explosions is greater than for contact explosions.

18-4. Upon application of pressure pulse loading to a submarine through underwater explosive attack, a very complex transient motion may be induced in the hull structure. Structural members may acquire a very high velocity which endures


1 A detailed study of shock and shock protection methods is contained in NavShips Publication 250-660-26 entitled "Mechanical Shock on Naval Vessels".

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for a sufficiently long time to impart a substantial displacement to, and within, these parts. The motion of these structural members is eventually arrested by other parts of the ship's structure and by their own internal damping and elastic properties. This results in a reversal of the initial motion, followed by a transient roughly periodic damped vibration which characterizes the return of the members to their original position in cases of elastic deformation or to some new position in cases of permanently distorted structure. The sudden initial acquisition of velocity is by definition characterized by a high acceleration acting for a short time. Since objects directly mounted upon these structural members are restrained to move with their supports, they must also reach closely equivalent velocities and as a result be subjected to high accelerations. These high accelerations can produce extremely high inertia forces in certain parts of the equipment. The stress effects produced by these forces may be varied and numerous, e.g., breakage of materials having low impact resistance, rupture of pipe joints, misalignment of machinery, mal-functioning of relatively delicate mechanisms such as circuit breakers, relays, tripping and latch mechanisms, and derangement of relatively delicate equipment such as gauges, meters, radio and sound equipment. The classic equation which determines the magnitude of these forces is F = Ma, where "m" is the mass of the equipment being accelerated and "a" is the acceleration imparted thereto. Instead of considering "a" as a peak value only, it should be regarded as varying with time. The force "F" therefore also varies with time. Multiplying the peak acceleration by the mass of the object being accelerated will give the true peak force applied to the object at that instant but an erroneous impression of the response of the object to this force may result unless the time duration of the acceleration is taken into consideration. For example, certain materials, such as medium steels, can withstand the high forces resulting from application of a high acceleration for a virtually instantaneous period of time but may fail if the time duration is increased, whereas other materials, such as glass, may fail when subjected to the brief but high acceleration only. The force "F" may induce stress in a member of the ship's structure due to accelerating a piece of equipment mounted upon such structure; it may result in a stress component induced in the casing or chassis of a piece of equipment due to a difference in acceleration of the components mounted upon such casing or chassis; or it may induce stresses in an internal component of a piece of equipment due to the relative acceleration of a sub-component. Damage to equipment may be reduced or prevented by interposing a flexible mount between the equipment and the structural member of the ship so that motion can take place between the structural member and equipment mounted thereon. The equipment is thus gradually accelerated to the velocity of the ship's structure or to some lower velocity, if at all; i.e., the acceleration lasts for a longer time at a reduced magnitude.

18-5. Because of the importance of shock resistance to submarines, consideration has been given over a long period of years to this factor in the design of submarines and their components. Research in this

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field became more active in 1935 with the explosion testing of riveted and welded full scale caissons and has been continued since by this Bureau and by many naval field activities and private concerns. Included in the shock protection program for submarines were: (1) the further replacement of low impact materials with high impact materials; (2) use of resilient shock mounts, principally rubber, felt and molded phenolic material, for small items such as gages, lighting fixtures, electronics equipment, and resilient mounts plus common foundations for auxiliary machinery vital to submerged operation (in conjunction with sound-isolation); (3) use of fitted foundation bolts and/or large diameter dowels plus common foundations to retain alignment and reduce the effect of impact forces for various auxiliaries not used in submerged operations and hence where sound-isolation was not required, and for massive equipment such as reduction gears, main motors, etc., for which resilient mounting was not easily adaptable; (4) shock mounting on resilient rubber mounts of the entire propulsion control cubicle; (5) careful detail design of equipment, where possible, to absorb deflection if necessary without failure, i.e., increasing the energy absorption ability of the equipment; (6) careful detail design of mechanisms to produce characteristics which were inherently shock-proof or which could be made so by the use of simple anti-shock devices; (7) proper location of equipment so that the most favorable supporting structure could be utilized, and arrangement of equipment so that ample external clearance was available for movement of the equipment as a whole, and ample internal clearance so that component parts, such as vacuum tubes, could move relative to each other without causing damage, and (8) numerous other improvements such as laminated main battery cell jars, substitution of silver-brazed and welded piping joints for cone and bolted joints, and such small details as lock washers to prevent nuts from backing off and anti-shock retaining devices for ferrule type fuses, vacuum tubes, etc.

18-6. As the National Emergency was at hand and the research work being conducted with caissons and models was not being completed as rapidly as deemed necessary, it was decided that the task would be completed more rapidly by tests with a full scale submarine. Accordingly a series of such tests was conducted at Portsmouth, N.H. in 1941 with TAMBOR (SS198), TROUT (SS202), GAR (SS206) for the purpose of determining the vulnerability of all of the features of modern submarines to underwater explosive attack. Each of the three submarines was submerged to periscope depth and subjected to the detonations of 300-pound charges of TNT placed at depths of about 60 feet and at varying ranges and orientation with respect to the vessels. The closest charges in all three of the submarine experiments were 33 yards from the hulls. These tests revealed important deficiencies and the data obtained from them by expert observers formed the basis of practically the entire shock protection program for U.S. submarines. Information from these tests, obtained before our entry into the war, influenced the course of shock-proof design on U.S. submarines more than the combined total of the subsequent voluminous war experience since very few deficiencies

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were brought to light by actual war service that had not already been disclosed by the 1941 tests.

18-7. As a measure of the effectiveness of the various shock protection measures incorporated in our submarines, the controlled depth charge tests on DRAGONET (SS293) during April, May and June of 1944 off Portsmouth, N. H., provide interesting comparative data.1 Explosive charge weights, number of shots, ranges, and depths of DRAGONET and the charges were selected to be identical with the tests conducted on TAMBOR, TROUT and GAR in 1941 except that the ranges were corrected for the increased thickness of hull plating on DRAGONET so as to obtain approximately the same severity of shock loading. During all of the shots, DRAGONET was submerged to periscope depth. Fifteen charges were fired at a depth of approximately 60 feet, the first containing 600 pounds of TNT and each of the others 300 pounds of TNT, and at various ranges from 1500 to 75 feet as shown in Figure 18-1 below. The depth of water was approximately 150 feet. The observed damage to the vessel and equipment for the various shots is contained in Table 18-1 below.

FIGURE 18-1


1 David Taylor Model Basin conf. Report No. R-283 of April 1945 (Shock Measurements During Depth Charge Tests on USS DRAGONET (SS293).

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TABLE 18-1

Observed Damage to DRAGONET During 1944 Vulnerability Tests

Shot

Location of Charge

Damage

1-5

Charges 1500 to 300 feet from the midship section on the port side.

No damage resulted.

6

Charge 200 feet from the midship section on the port side.

During this shot various running lights and upper deck instruments broke. Within the ship, the water circulating pump of main motor No. 2 was thrown out of alignment.

7

Charge 150 feet from the midship section on the port side.

No damage resulted. This was undoubtedly due to the fact that the charge was unintentionally fired close to the surface of the water, rather than at the usual depth, 60 feet.

8

Charge 138 feet from the midship section on the port side.

The auxiliary gyro compass spilled mercury, causing the instrument to operate improperly.

A pipe hanger in the pump-room was broken.

9

Charge 100 feet from the midship section on the port side.

The outer prism in periscope No. 2 was cracked and the instrument was jarred out of collimation.
Periscope No. 1 became defective on low power.
The selector switch for the conning tower lights was broken.
The vent of main ballast tank No. 1 leaked.
The gyro repeater lens on the bridge was broken, and the instrument was flooded. All gyro repeaters were affected.

10

Charge 75 feet from the after quarter on the port side.

Vents on a number of main ballast tanks were jarred open.

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Shot

Location of Charge

Damage

10 (cont'd

Charge 75 feet from the after quarter on the port side.

Both forward and after battery cells moved. Some wedges and strong-backs were loosened. Slight fissures appeared in the sealing compound of some cells.

An SJ-1 radar rectifier tube, Type 5U4, in the pump room was broken. This tube was not shock-mounted.

The voltmeter on lighting motor-generator set No. 2 was broken. The voltmeter on motor-generator set No. 2 was sticking. This meter was mounted on the control cubicle.

The ammeter on main generator No. 1 in the engine room was sticking. The gyro repeater system was rendered inoperative.

A non-shockproof lamp in a shock-mounted light fixture in the after engine room was broken.

The rudder steering gear became defective.

Sound heads, both port and starboard, became noisy when training.

The radar training mechanism became noisy.

Contact makers on a number of vents gave wrong indications.

The port shaft transmitter was jarred out of alignment.

Fuse retainers on the radar panel were jarred out of place.

Mercury was splashed from the master gyro compass. In addition there were various air, hydraulic, and water leaks, and some equipment had shifted position.

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Shot

Location of Charge

Damage

11

Charge 75 feet from the midship section on the port side.

A rough-service light bulb was broken.

The telephone selector was not operating.

The telephone ringer was broken.

(The preceding three items were in the forward torpedo room.)

12

Charge 75 feet from the forward quarter on the port side

Only minor damage was reported.

13

Charge 75 feet from the midship section on the starboard side.

The master gyro follow-up in the control room became inoperative.

A light bulb in the control room was shattered.

Three cells in the forward battery tank showed fissures in the sealing compound.

Threads were stripped from several strongback holding rods in the after battery tank.

14-15

Charges 75 feet from the after and forward sections, respectively, on the starboard side.*

* No examination was made between Shots 14 and 15.

The hand training gear of the starboard sound head became stiff; the repeater was off 2.5 degrees.

The port sound head became noisy when training; the repeater became erratic.

The WDA motor-generator became very noisy, and vibrated excessively.

The RBO speaker in the forward torpedo room was broken.

A voltmeter in the forward battery room was broken.

Several strongbacks in the after battery tank showed signs of springing.

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Shot

Location of Charge

Damage

14-15*

(cont'd)

Charges 75 feet from the after and forward sections, respectively, on the starboard side.

The F.W. tank on the starboard side of the after battery room showed a pronounced displacement, and the hangar bolts were bent.

A hanger holding a resistance box in the forward engine room was broken.

An ammeter on No. 1 main engine board in the forward engine room became sticky.

A voltmeter on No. 2 main engine room board in the forward engine room became sticky.

The after torpedo firing mechanism was not working.

18-8. DRAGONET represented a submarine on which practically all of the numerous items in the shock protection program had been accomplished. It is therefore significant to note that the shock damage resulting from the 1944 tests on DRAGONET was minor, even though the closest shot was fired at a range of 75 feet, whereas the 1941 trials of TAMBOR, TROUT, and GAR, on which only moderate shock protection had been accomplished, resulted in relatively serious shock damage although the closest shot was fired from 100 feet. The DRAGONET experiment demonstrates that considerable improvement has been made in the shock resistance of our submarines. However, it is known that the modern submarine can withstand depth charge attacks at ranges somewhat closer than the minimum range employed in the DRAGONET tests.

18-9. Several cases are available from war experience which afford a rough means of estimating the shock resistance of our submarines when subjected to near destruction from underwater explosions. The damage narratives of KINGFISH, TUNNY, SALMON, SCAMP and HALIBUT, included elsewhere in this report, represent five instances where considerable permanent pressure hull deformation was sustained by submarines on which all or a substantial portion of the shock protection program had been accomplished prior to their damage. A study of that portion of the damage suffered by these vessels which can be attributed to shock alone indicates that while properly shock-mounted vital equipment remained for the most part unaffected, although the submarines in each case were on the verge of being destroyed through failure of their pressure hulls, further improvements in shock protection is necessary particularly

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in piping and electrical systems. For example, damage to the control cubicles of TUNNY and SCAMP very nearly caused the loss of those vessels. It is interesting to note that in none of the cases cited above did sound-isolated equipment mounted on rubber compression type resilient mounts sustain any damage, nor has any report come to the knowledge of this Bureau, so far as can be determined, which indicates that equipment so mounted has ever received disabling shock damage on any U.S. submarine. This is significant since the problem of combining shock protection with sound-isolation is by its very nature a compromise, neither the shock protection nor sound-isolation reaching their optimum possible efficiency when provided concurrently by the same mount. War experience indicates that the degree of both shock protection and sound-isolation provided by properly mounting equipment on compression type rubber mounts is adequate. Various items of directly mounted machinery did sustain shock damage in all of the above actions, e.g., on HALIBUT the bedplates of the TBL motor generator, the ice machine compressor and the No. 2 air conditioning compressors were cracked. Damage to directly mounted auxiliary machinery has also occurred in cases where no pressure hull damage was sustained. In TAMBOR's (SS198) action of 3 February 1944, the bedplates of both high pressure air compressors in the pumproom were cracked around their complete periphery and both low pressure blowers were dislodged from their foundations. In GREENLING's (SS213) action of 25 January 1945, the bedplate of the No. 2 high pressure air compressor was cracked. In SARGO's (SS188) action of 14 June 1943, the crankcase of the No. 1 low pressure air compressor fractured, disabling the compressor.

18-10. General remarks regarding the shock resistance of various components of our submarines can be drawn from war experience as follows:

(a) Pressure hull structure. (Excellent) Areas of stress concentration under shock loading appear to have been held to a minimum through careful detail design (based on experience gained in controlled explosion tests of full scale models).

(b) Propulsion Diesel engines. (Excellent) With few exceptions, Diesel engines have remained operable even on vessels sustaining severe pressure hull deformation in way of machinery spaces.

(c) Main generators and propulsion motors. (Excellent) No reports have been received where direct shock damage has disabled propulsion motors or main generators.

(d) Propulsion electrical control equipment. (Good) Several cases occurred where propulsion was disrupted due to derangement of control equipment.

(e) Main reduction gears. (Poor) Very susceptible to tooth damage, causing high noise level.

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(f) Main battery. (Good) Laminated battery cells have occasionally cracked on vessels sustaining severe shock damage but the number where electrolyte was lost has in all cases been small.

(g) Resiliently mounted sound-isolated auxiliary machinery. (Excellent) No known cases of failure through shock damage.

(h) Directly-mounted auxiliary machinery. (Good) Several instances have occurred where directly mounted machinery has sustained fractured bedplates, misalignment, etc. However, directly mounted auxiliaries have in general been limited to those not essential for submerged operations.

(i) Piping. (Fair) Close attacks almost invariably cause piping leaks, frequently of serious nature.

(j) Auxiliary Power Systems. (Fair) Close attacks have frequently caused damage to or maloperation of relays, switches, controllers, etc.

(k) Torpedo tubes and firing gear.  (Fair) Frequent shock damage has occurred to outer doors, gyro setting and depth setting spindles, stop bolts, guide studs, etc.

(l) Instruments, gauges, meters and light bulbs. (Poor) Close attacks generally caused extensive derangements to such equipment.

(m) Periscopes. (Poor) Periscopes were very susceptible to damage of disabling nature. Periscope derangements were reported in over 30 separate actions. In at least three instances, periscope damage forced termination of patrols.

18-11 The Bureau is cognizant of the need for further improvement in the shock protection of our submarines and is currently engaged in a research and development program toward this end. Particular emphasis is being given to correction of weaknesses disclosed by war experience for those components whose performance has been only fair or poor. It is apparent that shock protection is a continuing and expanding problem in view of the present tendency towards submarines of greatly increased hull strength for operation at extreme depths. However, shock protection is not the problem of the design and research agencies alone. It is incumbent upon building and repair activities and ship's force to install and maintain such protection in thorough and complete agreement with the best and latest data available. Shock protection and sound isolation standards should be as vigorously observed in time of peace as in war.

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SECTION XIX

ENGINEERING NOTES

19-1. When it is considered that the propulsion plant of a modern U.S. submarine, including the batteries, occupies about one-half the length and over one-third the volume of the hull, it is certainly remarkable that the incidence of serious damage to such equipment due to war action was extremely low. In only one known instance, GRENADIER'S (SS210) action of 22 April 1943, was a propulsion plant completely and permanently disabled, and in only one other known case, PERCH's (SS176) action of 2 March 1942, was a propulsion plant damaged so heavily as to be a significant factor in the eventual loss of the vessel.1 However, propulsion power submerged was temporarily disrupted on our submarines in over fifteen separate occasions as the result of underwater explosive attacks, and with serious consequences in a few instances. All of these temporary power disruptions were caused by failure of electrical equipment, principally through tripping of relays and contactors due to shock or jarring together of energized control cubicle busses. They occurred for the most part early in the war on older ships, where shock protection measures had not yet been carried out. That serious damage did not occur more frequently to U.S. submarine propulsion plants was due principally to the following: (1) the inherent ruggedness of the propulsion motors, generators, batteries, reduction gears, Diesels, shafting and propellers; (2) the improvements made in the shock design and shockmounting of vulnerable equipment, particularly the introduction of laminated main storage battery cells, shock-proof relays, shockmounted propulsion control cubicles and fitted foundation bolts to prevent misalignment of the propulsion motors and reduction gears; and (3) effective casualty control through split plant operation.

19-2. Although many casualties were sustained by U.S. submarine propulsion and auxiliary Diesel engines in the course of normal service, there are only a very few instances in which these engines are known to have sustained damage as the result of war action. War experience has conclusively demonstrated that modern U.S. submarine Diesel engines, both propulsion and auxiliary, regardless of make, are practically impervious to damage of disabling nature, even at those explosive ranges which will cause near destruction of the pressure hull. The experiences of KINGFISH (SS234), SALMON (SS182), SCAMP (SS277), and HALIBUT (SS232) are excellent examples since all four of these vessels sustained permanent pressure hull deformation in way of the machinery spaces.2 No damage at all was received by the Diesels on KINGFISH and HALIBUT. On SCAMP, No. 2 propulsion engine (FM Model 38-D-8-1/8) was disabled when the pressure hull bulged sufficiently to come hard up against the scavenging blower of that engine (Photo 9-11). SCAMP's other engines remained completely operable, however. On SALMON, all engines


1 GRENADIER narrative, Section VIII and PERCH narrative, Section IV.
2 KINGFISH, Section V; SALMON, Section VII; SCAMP, Section IX; HALIBUT, Appendix I.

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(GM Model 16-278A) either partially or completely flooded through leaking exhaust lines, but none were physically damaged by the attack. However, the drive shaft of the scavenging blower for No. 1 propulsion engine subsequently fractured when an attempt was made to start the engine before dewatering had been completed. SALMON's other three engines operated satisfactorily. On GRENADIER, in the action leading to her loss on 22 April 1943, the propulsion Diesels apparently remained operable after the bomb attack although severe hull damage was sustained in way of the machinery spaces, for it was reported that smoke was cleared from the interior of the boat, after surfacing, by running the engines. On PERCH, two engines remained operable after the first series of depth charge attacks but only one engine could be run after the second series of attacks. One engine limited her surface speed to about five knots. One of the three damaged engines (Winton Model 16-201A) was disabled by a broken camshaft. The cause of failure of the other two engines was not reported. The auxiliary Diesels were not damaged.

19-3. The most frequent casualties which occurred to Diesel engines incident to close underwater explosive attacks were the following: engines flooded through leaking exhaust valves;1 lube oil, fuel oil and circulating water lines ruptured or developed leaks, usually minor; engine foundation bolts sheared; and engine thermometers and other gages were broken or deranged. Such casualties are of minor nature, in no case have disabled an engine for more than a temporary period, and are not peculiar to war damage since similar casualties have occasionally resulted during normal service operations, due to leaking exhaust valves or excessive engine vibration. That our submarine Diesels have withstood close attacks with out minor or no damage occurring is attributable to the following reasons: (1) the rugged welded steel construction of the engine frames, resulting in high energy absorption characteristics, (2) the rugged construction of the engine components, and (3) the large mass of the engines. Assuming both to be directly mounted, the relative shock strength of a heavy item of equipment, such as a propulsion Diesel engine, need not be as great as the strength of a small and light item, as for example, a relay or an instrument. This is because a large, heavy item has a weight comparable in magnitude to the weight of the ship's hull and the foundation in the immediate vicinity of the equipment, and consequently the large mass and rigidity of the engine and its structural foundation modify the shock motion of the hull locally. Moreover, the rigidity of a Diesel engine is comparable to or may exceed that of the foundation and hull, so that for severe shock motions the hull and foundation will tend to absorb a relatively large percentage of the shock displacement, whereas the engine will remain almost stationary. In the case of a heavy machine, the forces that can be transmitted to the machine by shock may be limited by the strength of the foundation.

19-4. The propulsion motors and generators have also been singularly free from war damage casualties and for reasons similar to those


1 SALMON, Section VII; and PERMIT, 13 February 1944, Appendix I.

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enumerated above for the Diesel engines. There is no known case where propulsion motors or generators have been disabled on U.S. submarines through direct war damage to the motors or generators themselves, regardless of their type and make. In one case, SAILFISH's (SS192) action of 7 December 1943,1 a propulsion motor arced to ground and sustained brush rigging damage which disabled it until repairs were accomplished by ship's force, but this casualty was caused by failure of control equipment in the cubicle rather than direct damage to the motor itself. There are a few instances where brush rigging on propulsion motors has been slightly deranged or has jarred slightly out of position but the effects have been minor in all such cases. Reports have also been received where brush rigging on propulsion motors has been dislodged through shearing of rivets, or where brushes have overheated or chattered, and these casualties have been attributed to close depth charge or bomb attacks. However, it is believed that most of the latter cases were due to improper securing of the brush pigtails since such casualties also resulted from normal service operations. Corrective steps were taken in the manufacture of these brushes in 1944 and, so far as is known, no further brush difficulties were encountered thereafter. No reports have been received by the Bureau of any war damage having occurred to main generators. This is partly attributable to the fact that the generators are not energized during submerged operations and therefore derangements of control equipment will not cause minor damage to the generators, as has occurred in a few cases to propulsion motors.

19-5. The only component of submarine propulsion plants which war experience demonstrated to be particularly vulnerable to damage and which frequently caused loss of propulsion, was the propulsion electrical power and control gear, principally the equipment contained in the propulsion control cubicle. Of the fifteen cases known to the Bureau where propulsion failed temporarily on submarines while submerged and undergoing attack, all were due to electrical casualties. These casualties can be divided into three general types: (1) tripping of propulsion overload relays due to shock (later replaced by shockproof overload relays), (2) operation of relays due to momentary movement and short-circuiting of energized bus bars in the control cubicle and (3) control cubicle electrical fires caused by short-circuiting of energized circuits. The urgent need for improving the shock resistance of submarine propulsion electrical control equipment was demonstrated by the controlled depth charge tests conducted with TAMBOR (SS198) and TROUT (SS202) early in 1941, before our entry into the war. Two principal corrective measures were proposed: (1) improving the shock resistance of the separate components, such as switches, contactors and relays, and (2) the shockmounting of the entire propulsion control cubicle to reduce the acceleration forces on vital equipment contained in that enclosure. Following the tests on TAMBOR and TROUT, the submarine GAR (SS206) was provided with the first experimental installation of a shockmounted propulsion control cubicle, designed and constructed by the General Electric Company and employing


1 See Appendix I for brief of SAILFISH damage.

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rubber pads as the resilient material for shock reduction. Several experimental overload relays were also installed in GAR to test the relative merit of various designs. Controlled explosion tests were then conducted which demonstrated that shockmounting of the entire control cubicle was a practicable method of reducing damage to the vital electrical control gear and that the designs of switches, contactors, and relays could be so improved as to provide a high degree of inherent shock protection. The Bureau therefore authorized the shockmounting of propulsion control cubicles on both submarines in service and new construction.1 In addition, overload relays in the main battery power and propulsion motor and generator circuits were replaced with shockproof types and, on applicable submarines, lock-out cams were installed to prevent maloperation of the series and parallel contactors in the main control cubicle.2 As a result of TUNNY's (SS282) experience of 26 August 1943, where propulsion power was disrupted temporarily due to a fire which started when the positive and negative main battery busses in the control cubicle jarred together momentarily, the installation of small phenolic bumpers between the cubicle main battery busses was authorized for all applicable submarines to prevent recurrence of similar casualties.3

19-6. The effectiveness of the shock protection afforded by the above alterations can best be judged by the fact that so far as is known, with only four exceptions, all cases of loss of propulsion power traceable to derangement or maloperation of electrical equipment occurred prior to 1944 and on vessels which were not provided with shockproof relays and/or shockmounted control cubicles. The four exceptions were as follows:4 (1) TUNNY's action of 30 March 1944 in which energized bus bars short-circuited by movement against the control cubicle frame. This damage is believed traceable to the fact that, although the cubicle had been shockmounted, the shock protection afforded by the resilient mounts was reported to have been nullified by one support frame which was improperly mounted so that it made direct metallic contact with the cubicle cage. (2) PICUDA's (SS382) action of 20 May 1944 in which a close depth charge detonation tripped the starboard propulsion motor contactor in the control cubicle. The contactor was immediately closed, however, and propulsion was restored. (3) SANDLANCE's (SS381) action of 7 August 1944 in which the starboard propulsion control cubicle controllers were jammed by a broken washer and limited the maximum speed on the starboard shaft to two-thirds until repairs were made. (4) COBIA's (SS245) action of 14 May 1945 in which the battery and generator busses in the control cubicle arced, causing flame and smoke and the welding together of the contactors. Power was secured and the ship went to the bottom.


1 Authorized for new construction by BUSHIPS Itr. SS212-284/S41 (3660) of 11 December 1941 and for ships in service by ShipAlt SS131 of 7 August 1942 (delay for ships in service was due to priority assignment of materials and design work for ships being constructed).
2 ShipAlt SS218 of 17 November 1943.
3 ShipAlt SS222 of 6 November 1943.
4 Briefs of damage sustained by each of these four ships are contained in Appendix I.

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19-7. The importance of insuring that foreign objects and inadequately attached fittings are removed from areas over or adjacent to propulsion control cubicles has been illustrated by several experiences where propulsion power was lost and/or fires were started due to short-circuiting of energized power circuits by small objects falling from the overhead or being hurled into the cubicle from the sides. SCAMP's action of 7 April 1944 (Section IX) is such an example.

19-8. The presently accepted standard U.S. submarine main storage battery jars are of laminated construction having a hard rubber exterior and a soft rubber inner layer. War experience has demonstrated that battery jars of this type are highly resistant to shock and can be considered generally satisfactory for war service. The introduction of laminated battery jars together with improvements in the design and support of the battery tanks are major factors in the resistance of submarines to damage. The lining of the battery tanks with rubber also probably contributes to the shock-proofness of the batteries. Submarines which have sustained close attacks, but where no pressure hull deformation occurred in the vicinity of the battery tanks proper, have in all cases either had no battery jar damage at all or the jars have cracked on only a very small number of cells. It is also significant to note that in the majority of those cases where jars were reported as having cracked, no loss of electrolyte occurred since only the outer hard rubber exteriors of the jars cracked and the inner soft rubber portions remained intact. Even where jars have lost electrolyte and caused short-circuiting, no serious consequences have resulted since the damaged jars were easily disconnected. In only two instances have relatively large numbers of battery jars been damaged on U.S. submarines which survived close attacks; on HALIBUT (SS232), 14 November 1944; and on REDFISH (SS395), 19 December 1944. In both of these cases the battery jars were of laminated construction. On HALIBUT, the hull forward of frame 55 was extensively damaged and the pressure hull plating in way of the forward battery well was dished in by as much as from one to two inches. About seventy percent of the 126 jars in the forward battery developed cracks through their outer hard rubber casings (Photo 19-1). On all but eleven jars, the soft rubber inserts were undamaged and no leakage of electrolyte occurred. On the eleven jars which lost electrolyte, the leakage occurred through cracks in the jar bottoms. The fact that only eleven jars actually leaked, although a total of about eighty jars had cracks in their outer casings, is convincing evidence of the value of the laminated soft rubber insert construction. No damage was reported to have occurred to the after battery jars. On REDFISH, the forward portion of the pressure hull was also considerably deformed although no dishing was reported in way of the forward battery well itself. Twelve jars of the forward battery were cracked and lost electrolyte. No damage was sustained by the jars of the after battery. In neither of the above two cases did the damage to the batteries have serious effect on ship operation. When the extensive pressure hull damage which occurred close to the battery wells on both HALIBUT and REDFISH is compared with the battery damage on those two vessels, it appears that current submarine battery cells and their method of installation approach the shock resistance of the hull itself.

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19-9. In numerous instances, full battery grounds have developed as a result of close attacks. In most cases these have been traceable to short-circuits in the emergency lighting systems or short-circuiting of one or more cells caused by electrolyte spillage through cracks which developed in the battery cell top sealing compound and thence establishing leakage paths to uninsulated tie-rods and strongbacks connected to hull structure. Cracks occurred in the sealing compound due to shock but in many cases this tendency was aggravated by improper wedging or faulty tightening of strongbacks. To eliminate casualties due to acid spillage through cracked sealing compound, two steps were taken: (1) all tie-rods and strongbacks in the battery wells were insulated with a rubber compound, and (2) improved sealing compounds were developed. To facilitate locating the cause of battery grounds, switches were installed in the emergency lighting circuits on all fleet type submarines to permit separation of emergency lighting from the battery for battery ground readings.1

19-10. War experience has repeatedly demonstrated that reduction gear drive propulsion plants are unsuitable for modern submarine warfare in that the main reduction gears are extremely susceptible to tooth damage when subject to underwater explosions at even moderate ranges. Tooth damage causes high noise level, usually described as 'clicks", "thumps", or "knocks", which reduces or invalidates the military effectiveness of submarines since approach and evasion tactics then become hazardous or impossible when enemy vessels are equipped with sonar listening gear. In approximately eighteen instances, U.S. submarines have reported that excessive reduction gear noise developed as the result of enemy depth charge or bomb attack. In at least three actions, reduction gear damage forced early termination of patrols and the subsequent repairs to achieve quiet operation were long and expensive.2 Reduction gear damage has in no case prevented the gears from operating mechanically but has been objectionable from the standpoint of the introduction of high noise level. Tooth damage has apparently resulted either from sudden and violent movements of the pinion and bull gear masses relative to each other or in some cases perhaps from longitudinal movement of the entire propeller shafting. For example, a clicking noise developed in the reduction gears of APOGON (SS308) when forward area repair forces removed a damaged propeller on that ship, without drydocking, by detonating small explosive charges on the forward blade faces. Since the shaft coupling in the motor room was not broken, the shaft tended to move aft as a whole and caused sudden relative movement of meshing tooth surfaces in the reduction gear. A similar action could probably occur on a submarine when subjected to close underwater explosive attack In addition, the continuous reduction in self-generated noise accomplished by design improvement of components and by sound isolation measures resulted in the noise caused by reduction gears, even though undamaged, to become a prominent noise feature, whereas in earlier fleet submarines, the re-


1 ShipAlt SS224 of 21 December 1943.
2 SAND LANCE (SS381), 7 August 1944; BARBERO (SS317), 27 December 1944; and BERGALL (SS320), 13 June 1945. See Appendix I and Section XIV for details on damage.

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duction gear noise was not as high as that of other items. This, together with the war experience in regard to damage, led the Bureau to change from reduction gear drive for submarines to direct drive. The move, which required considerably more weight for the low speed direct drive motors, was made possible by weight savings that had been realized through careful design of various components and by the elimination of unnecessary ones.

19-11. Main engine air induction and ship's supply ventilation hull flapper valve discs and/or their seats have in several instances been deformed by close explosive attack. When the induction line itself concurrently flooded, as sometimes occurred, sea water then entered the machinery spaces, occasionally in considerable volume. Early in the war, leakage which developed around these hull flapper valves was in several instances successfully stopped or reduced to a minor quantity by forcing the valve flapper against its seat with the aid of a chain fall as on KINGFISH during her action of 23 March 1943 (paragraph 5-21, Photo 5-8). In July of 1943, gagging dogs were authorized for installation on engine air induction and ship's ventilation hull valves on those submarines not previously provided with emergency means of securing such valves.1 It should be noted that leakage through induction valves will always accumulate in after compartments and therefore may cause a submarine to become heavy aft, flooding of the topside induction piping also contributing to this tendency. The majority of instances where U.S. submarines have lost depth control due to flooding have been the result of added weight aft through induction hull valve leakage. The introduction of welded joints for the induction piping topside, commencing early in 1944, practically eliminated cases of flooding of such piping and therefore the prospect of flooding into the interior of the hull through distorted induction hull valves has been reduced markedly. Projected submarine designs will incorporate a snorkel type air intake and consideration will be given to running the induction piping system leading from the snorkel intake to the machinery spaces entirely within the confines of the pressure hull. The number of large openings in the hull for air purposes would thereby be reduced to only that at the snorkel itself.

19-12. Wiring passing through the pressure hull to external instruments or fittings exposed to full sea pressure has proved to be quite vulnerable to damage unless special precautions are taken. The failures encountered have been of two general types: (1) leakage through cable sheathing causing direct shorting of the cable conductors or allowing water to reach terminal boxes, switchboards, or equipment, and (2) leakage around pressure hull stuffing boxes. As an example of the former, the experience of SCULPIN (SS191), on her second patrol is interesting. On 7 February 1942, while undergoing depth charge attack at a depth of 345 feet, the multiple conductor to the port annunciator flooded through the annunciator box on the bridge. Water then passed


1 ShipAlt SS201 of 7 July 1943.

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through the length of the cable to the IC board in the control room, started a small fire, grounded numerous circuits, and ultimately placed the entire torpedo firing circuit and battle order transmitter and indicator systems out of commission. There are many cases on record where cables passing through the pressure hull have been forced inward through their stuffing tubes during close attacks, some by as much as one or two feet. In such cases, leakage has usually occurred at the stuffing tubes. Several corrective measures were taken to eliminate such casualties. Following a method developed by the Naval Shipyard, Portsmouth, rubber stop rings were vulcanized directly to cable sheathing at the outboard sides of all pressure hull stuffing tubes, using special molds for each size of cable, to prevent cables from being forced in.1 Cable ends external to the pressure hull were terminated with vulcanized seals to prevent water entering the sheathing. Similar methods were developed for packing terminal tubes and sealing cable ends for cables entering pressure proof fixtures. On older vessels, external cables no longer required for ship operation were removed and the hull stuffing tubes blanked. Cables leading from conning tower equipment to the main pressure hull, which formerly were routed outside the hull and therefore exposed to full sea pressure, were rerouted through a specially enlarged conning tower hatch trunk so as to be entirely within the pressure hull,2 and an additional cable trunk was authorized for installation between the conning tower and control room to accommodate the additional cable required for SJ radar and other new equipment. Casualties to external cables were practically eliminated in those vessels on which the above alterations were accomplished. In those few cases where cable sheathing leaks did occur subsequent to the above alterations, it is believed that the cause of leakage can be traced to improper cable end sealing.

19-13. On 17 August 1942, a serious fire occurred in the after battery tank of BASS (SS164) while operating off Balboa, C. Z., on her fourth war patrol. The fire was believed to have been caused by a short circuit resulting from leakage paths across phenolic insulation. Twenty-six members of the crew in after compartments, most of whom were asleep when the fire started, were trapped and died either through asphyxia or from the toxic effects of the fumes generated by burning phenolic material. In order to eliminate the possibility of similar casualties on other submarines, instructions were issued to remove phenolic material from certain places in submarine battery tanks.3 On 7 April 1944, another serious casualty resulted from burning phenolic material, this time on SCAMP (SS277), and very nearly caused the loss of the vessel.4 On that ship, large quantities of toxic phenolic smoke were generated by a very small electrical fire at a phenolic-insulated rotary switch in the control cubicle. The Bureau was long aware of the undesirable properties of phenolic resins for shipboard insulation use and during the war years many research and development contracts were let with industry with


1 Authorized by BuShips ltr. SS/S62-2(660u-815); EN28/A2-11 of 31 March 1944.
2 Authorized by BuShips conf. ltr. SS/S62-2(515) of 2 March 1944.
3 BuShips ltr. SS/S39-1(8660-3660); EN28/A2-11 of 10 October 1942.
4 See SCAMP narrative, Section IX.

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the view of obtaining a more satisfactory material. By early 1944 a new organic insulation material made of melamine resin rather than phenolic resin had been accepted. Tests demonstrated that the insulation and shock properties of melamine were equal to or greater than those of phenolic but that melamine would not support combustion. Phenolic material, once ignited, will continue to burn and will generate large quantities of toxic fumes, whereas the combustion of melamine will result in only 40 percent toxic gases as compared with phenolic material, will only decompose when actually subjected to high temperature, as from an electric arc caused by short-circuiting, and all combustion will immediately stop when the source of heat is removed. It is possible on SCAMP, for example, that the volume of toxic gases given off by the burning phenolic material was very much greater than the volume of gases which would have been generated had melamine material been installed. By May of 1944, melamine production had reached a sufficient volume so that its use as an insulation material combined in laminated construction with glass cloth was authorized for submarines, the first installations being made in the split-type control cubicles on direct drive submarines then under construction. The introduction of melamine insulation for submarine electrical equipment is considered to have greatly reduced the hazard from toxic gases originating from electrical fires and constitutes an important peacetime safeguard as well as a wartime necessity.

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Photo 19-1: HALIBUT (SS232). View showing cracks in hard rubber outer casing of laminated battery jars on HALIBUT (SS232) as a result of her action of 14 November 1944. Although about 80 jars of the forward battery developed cracks in their outer casings, only 11 jars lost electrolyte.

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SECTION XX

PIPING

20-1. Leakage from air systems in submarines as a result of war damage can be a matter of great concern, particularly in the case of air leakage which occurs in main ballast tanks or at other points external to the pressure hull. The high pressure air system naturally constitutes the greatest potential air leakage hazard on submarines since that system is normally maintained at a pressure of about 3000 pounds per square inch, the piping extends throughout the entire length of submarines, and the major portion of the air reservoir is contained in air banks located in ballast tanks external to the pressure hull.

20-2. Depth charge vulnerability tests conducted with TAMBOR (SS198), TROUT (SS202), and GAR (SS206) early in 1941 demonstrated conclusively that cone joint connections in high pressure air systems did not satisfactorily withstand attack at close range. In so far as shock is concerned, cone joints are fundamentally undesirable since such joints are relatively loose and will pound when subjected to sudden and violent movements. This will cause large stresses to be built up, and, as the tightness of a cone joint is dependent upon metal to metal contact of the "belled" portion, any accompanying distortion of the sealing surfaces will result in leakage. The Bureau therefore authorized an extensive program to convert the high pressure air system joints on all fleet type submarines to silver-brazed connections and special union-type fittings having plastic annular ring seals.1 Although this program commenced in November 1941, the magnitude of the work involved required that the changes be accomplished on submarines during their regular overhaul periods, and consequently many of the submarines then in service were not modified until late in 1942 or early in 1943. In addition, the high pressure air systems on submarines in service and those in late stages of construction were in most cases only modified to cover the joints in the ballast tanks, battery compartments and easily accessible internal fittings, so that cone joints still remained in numerous locations on many ships even up to the end of the war. As a corollary alteration to the joint modifications, it was directed that all high pressure air flasks in fuel tanks be removed and reinstalled in main ballast tanks to eliminate the possibility of air leaks in fuel tanks causing oil slicks or tank rupture.

20-3. Throughout the war, there were at least twenty-five instances in which high pressure air systems on U.S. submarines developed leakage following depth charge or bomb attacks. In most of these cases, the air leakage was relatively small and had no serious consequence. The KINGFISH, TUNNY, TANG, and HALIBUT actions are among the few instances where there was important internal air leakage.2 On


1 Authorized by ShipAlt SS62 of November 1941. The modification of fittings in tanks external to the pressure hull was classed as a Class "A" Alteration. Modification of fittings within the pressure hull was classed as a Class "B" Alteration.
2 See KINGFISH narrative, Section V; TUNNY narrative, Section VI; TANG narrative, Section X; and brief of HALIBUT damage, 14 November 1944, Appendix I.

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KINGFISH (SS234) and TUNNY (SS282), the leakage occurred at cone joints of the high pressure air receiving and distributing manifolds. The resulting increase in internal air pressure on KING FISH, was reported to be one of the factors which eventually forced her to surface. In the case of the air leakage which occurred on HALIBUT (SS232) one of the "tee" fittings at No. 1 high pressure air bank in the forward battery compartment carried away and the entire bank bled down rapidly.

20-4. Although many instances were reported where high pressure air lines within ballast tanks developed leakage, in none of these cases was a submarine forced to surface due to increase in buoyancy through rapid accumulation of air pockets in the tanks. In at least one case, THRESHER's action of 9 July 1944, air bubbling to the surface from main ballast tank high pressure air leaks (vent valves were open) is believed to have enabled detection by the enemy.

20-5. Instances where high pressure air leakage developed as the result of enemy attacks continued to occur up to the end of the war. However, these casualties were limited for the most part to older submarines in which the cone joints of existing high pressure air systems had either been modified for silver-brazing or were still installed. There were remarkably few cases of high pressure air leakage on those later vessels which were built with air systems having all connections either silver-brazed or fitted with special union joints. Silver-brazed connections are believed to be completely resistant to depth charge attack when properly installed. The most important factor in proper installation is to insure that the clearance between the fitting and the piping is correct so that the brazing material will flow by capillary action. A good installation is facilitated by the use of fittings of the approved pre-inserted ring type, and tests have demonstrated that failure should occur in the pipe or fitting rather than the joint. It is believed that all cases where silver-brazed high pressure air system joints failed on submarines were due to one or more of the following reasons: imperfect brazing technique; excessive clearances in joint assemblies; the use of existing fittings which perhaps were excessively weakened when modified for silver-brazing, or the use of fittings which were reheated too many times either during the initial installation or through repeated use. The resistance of silver-brazed joints to explosive attack is dependent in very large measure upon the skill of the silver-brazing operator, the quality of the supervision and the methods of inspection. The special union-type joints using plastic annular ring seals have proved remarkably resistant to damage, there being no reported case in which serious leakage can be identified as having occurred at such joints through war action.

20-6. The forward and after main ballast tank vent risers, as installed on submarines prior to SS417, pass through the forward and after torpedo rooms and are subject to full sea pressure at all times. In addition, when a submarine is under attack these risers are exposed to explosive loading from close detonations. During the war a number of cases of leakage at the flange joints were experienced. In one case, the copper riser had been dented in installation to clear an interference and under depth charge attack the dent was straightened out, fouling a passing shaft. As a result of these factors there was considerable concern in the submarine service over the hazard involved in having these risers, open to the sea, passing through the torpedo rooms. There were in

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service two types of risers, steel and copper. The copper risers had been installed to avoid corrosion and loss of strength in service. Both types were stronger than the pressure hull. However, the copper risers and their bronze flanges were subject to plastic deformation and were thus more vulnerable to flange leakage than the steel risers. The flanges of the steel risers involved no greater hazard, if properly installed, than any other flanged hull connections. It was usually possible to stop any leakage by tightening the flange bolts. However, in one case, TUNNY's action of 1 September 1944, damage by bomb attack caused leakage at the flanges of the internal port vent riser of main ballast tank No. 7 in the after torpedo room and this leakage was the determining factor in the Commanding Officer's decision to terminate the patrol (Photo 20-1).1

20-7. Measures were instituted during 1943 in an effort to improve the resistance of internal ballast tank vent risers to flange leakage. The copper risers and bronze flanges then in service were replaced with new risers of seamless drawn or specially welded steel tubing fitted with steel flanges.2 All new construction submarines were already being provided with steel risers. Steel is a more satisfactory material for such service since its strain energy within the elastic range is much greater than that of copper. Instructions were issued to make special efforts to secure tight joints during the assembly of internal riser piping by truing the flanges to avoid bolting strain, by using pressed asbestos gasket material rather than rubber or cloth inserted rubber gaskets, and by installing lock washers under the flange nuts to prevent backing off. In addition, branch lines were eliminated in order to reduce the number of joints. It is believed that the major cause of trouble with these risers was improper installation in which the flanges were not properly regulated and in which the bolts were overstressed or thick rubber gaskets were used to correct improper flange fit. However, it was recognized that the psychological effect of such risers should be eliminated and a rearrangement of tankage in new construction submarines was undertaken in order to relocate the torpedo room main ballast tanks so that no vent risers would be required. Commencing with the SS417 Class, the forward ballast tank was located ahead of the forward torpedo room in the position previously occupied by the forward trim tank, and the after ballast tank was eliminated completely, displacing it with a variable fuel oil tank. Although the internal risers on submarines previous to SS417 will continue to be a source of concern under attack, and are therefore undesirable, it is considered that the hazard is one of flange leakage, usually in controllable amounts, rather than of sudden rupture leading to the loss of the vessel. The strength of the steel vent risers is considerably greater than that of the hull and consequently the risers are less liable to rupture than the adjacent pressure hull. War experience demonstrated that the strength of the risers was sufficient to prevent failure even in cases where adjacent pressure hull structure was considerably deformed.


1 See brief of TUNNY damage of 1 September 1944 in Appendix I.
2 Ship Alt SS171 of 16 March 1943.

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20-8. The hydraulic systems of U.S. submarines extend throughout the entire length of the vessels but, unlike the high pressure air system, are wholly confined to the spaces within the pressure hull. Hydraulic power has been extensively developed by the U.S. Navy for submarine applications and on vessels now in service the following vital equipment is hydraulically operated: rudder, diving planes, periscopes, radar masts, negative and safety tank floods, main engine air induction outboard valves, ballast tank vents, engine exhaust valves, sonar hoists and torpedo tube outer doors. Hydraulic system piping must therefore be extremely resistant to depth charge attack. War experience demonstrated that such piping frequently developed minor leakage at joints and connections as a result of close attacks, but that, with few exceptions, the numerous cases where failures in hydraulic power occurred could generally be traced to causes other than loss of hydraulic oil through leakage. By far the most frequent cause of hydraulic power failure was the loss of auxiliary electrical power supplying the main hydraulic IMO pump motors and the motors driving the Waterbury hydraulic pumps for the diving planes and steering gear. These failures occurred when the submarines concerned were not rigged for silent running and in such cases hydraulic control of equipment was usually quickly regained by shifting to hand hydraulic power. Although there were numerous cases where minor leakage developed at cone joint fittings and a few instances where leakage occurred at silver-brazed or special joints as the result of close attacks, such leakage was generally of small amount and, at cone, flanged or union joints, usually could be easily stopped.

20-9. There are several instances where hydraulic piping derangements caused loss of power to vital equipment. For example, SALMON (SS182), in her action of 30 October 1944, temporarily lost steering control when the hydraulic supply line from the Waterbury pump tore loose at the steering hydraulic manifold.1 However, steering was soon restored by shifting to hand power and later to emergency power. THRESHER (SS200) was forced to terminate her tenth patrol when, as a result of depth charging on 13 November 1943, sea water entered the hydraulic system through a leak in the external replenishing tank or piping forward of the conning tower. These external hydraulic oil replenishing tanks constituted an obvious weakness and were subsequently removed on all submarines to prevent recurrence of sea water contamination, as on THRESHER, and to place hydraulic systems entirely within the protection of the pressure hull. On REDFISH (SS395), as a result of a depth charge attack on 19 December 1944 during her second war patrol, the entire main hydraulic system was temporarily put out of commission by loss of hydraulic oil due to leakage at piping connections at the pump-room accumulator, steering manifold aft, and sonar and bow plane tilting piping forward.2


1 See Paragraph 7-31.
2 See brief of REDFISH damage in Appendix I.

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Photo 20-1: TUNNY (SS282). View showing damage which occurred to port vent riser of MBT No. 7 in after torpedo room of TUNNY (SS282) as a result of her action of 1 September 1944. Patrol was terminated due to excessive leakage which occurred around bolts of the two flanges shown, rendering submerged operations dangerous. Pulling of flanges is indicated by the absence of the cork insulation in their immediate vicinity.

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20-10. As a result of the TAMBOR, TROUT and GAR tests in 1941, which disclosed that the cone joints in hydraulic systems would start minor leaks when subjected to shock and that such leaks could be a considerable nuisance when located in relatively inaccessible areas, the Bureau directed that hydraulic piping on new construction submarines thenceforth be provided with silver-brazed sleeve type joints in lieu of cone joints, with the exception that special joints approved by the Bureau, such as union plastic seal ring joints or Van Stone joints, were to be used where piping must be dismantled to permit overhaul of machinery. The resistance of submarine hydraulic systems to shock damage was markedly increased by the introduction of silver-brazed and union plastic seal ring joints in lieu of the cone joints. However, the fact that close attacks continued to cause hydraulic system leakage up to the end of the war certainly indicates that further improvements are required before these vital systems can be considered to be as invulnerable to damage as their importance warrants. The experience of REDFISH (SS395), mentioned in paragraph 20-9 above, is illustrative of this need. Van Stone type joints, of which many remain in current hydraulic installations, appear to be fundamentally less desirable for severe shock service than silver-brazed and union plastic seal ring joints. Unfortunately, those reports received from submarines noting hydraulic system leaks have rarely identified the types of joints or connections at which the leakage occurred. Leakage has occurred at silver-brazed joints, however, and the remarks in paragraph 20-5 above apply with equal force to the quality of silver-brazed joints in hydraulic systems.

20-11. Impulse air systems for the forward torpedo tubes have on several occasions developed leakage at points outside the pressure hull as the result of close attacks. The air reservoir for the forward impulse air system on U.S. fleet type submarines consists of shatterproof flasks located in the forward superstructure. Since this location is external, the air flasks and piping to the pressure hull are subject to full explosive loading, and any leakage which may develop external to the pressure hull will result in air bubbles rising to the surface. Unfortunately, sufficient space is not available in the forward torpedo room to permit interior stowage of these bulky impulse air flasks. In at least one instance, external leakage from the forward impulse system had serious consequences. On 14 January 1943, during her sixth war patrol, PIKE (SS173) was heavily depth charged by several Japanese destroyers.1 Six hours after the initial attack, PIKE planed up to periscope depth but was promptly bombed by an enemy plane. Periscope observations at this time disclosed that large air bubbles were rising to the surface from the impulse air system forward and this evidence of PIKE's location undoubtedly enabled the enemy to make the prompt attack. The external portions of the forward impulse systems are considered to be inherently vulnerable to damage for the following reasons:


1 See brief of PIKE damage in Appendix I.

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(a) the flasks are in an exposed location;

(b) the joints in the piping leading from the flasks to the torpedo room are of bolted flange type construction;

(c) the bolted through-connection for each pipe at the hull is particularly vulnerable to damage should the adjoining pressure hull sustain deformation;

(d) on war patrol, the flasks are normally maintained with air at pressures in excess of 300 pounds. It is hoped that investigations now underway on methods of ejecting torpedoes without the use of air may perhaps eventually permit the removal of torpedo impulse air systems.

20-12. Main engine air induction and ship's supply ventilation outboard piping sections as installed on U.S. submarines through 1943 were connected with bolted flanged joints. These joints were the source of leakage into the induction and ventilation systems in numerous instances where close attacks were sustained. In approximately 20 cases, the leakage was serious enough to warrant mention in war patrol reports as a major defect. Sudden flooding of induction systems in several instances caused immediate loss of depth control on the submarines concerned. In addition, when the induction or ventilation hull valves were damaged at the same time the outboard piping flooded, leakage occurred into the engine and maneuvering spaces, in some cases with serious consequences.1 As a result of numerous casualty reports, authority was granted in January 1944 to eliminate all bolted flanged joints and substitute welded joints in the main induction and ship's supply ventilation piping.2 There are only a few instances on record where submarines have sustained main induction or outboard ventilation leakage after this alteration was performed, SEAHORSE's (SS304) action of 18 April 1945 being one notable case. It is significant to note that although three submarines received very heavy damage on patrols subsequent to being provided with welded joints, on none of these three boats was leakage into the main induction piping reported.3

20-13. In two instances, main induction piping partially or completely collapsed under close attack: SALMON (SS182), Section VII; and SCAMP (SS277), Section IX. In addition, on SCAMP the main induction pipe wall was torn in four places by its welded bracket supports.4 The fact that collapse of main induction piping occurred on the above mentioned ships demonstrates that the strength under explosive loading of the induction


1 See WHALE (SS239), 30 October 1942, Appendix I; PERMIT (SS178), 13 February 1944, Appendix I; GRENADIER (SS210), Section VIII; and KINGFISH (SS234), Section V.
2 BuShips conf. ltr. C-SS/S48-23(515); EN28/A2-11 of 10 January 1944.
3 ICEFISH (SS367), 26 October 1944; HALIBUT (SS232), 14 November 1944; REDFISH (SS395), 19 December 1944. See Appendix I for briefs of damage.
4 See SCAMP, Paragraph 9-22 and Photos 9-5 and 9-6.

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and ventilation outboard piping on those two Classes was less than that of the pressure hulls. There are no known cases where induction piping has collapsed on SS285 Class and subsequent submarines. It should be added, however, that these large tubes running for long distances outside the pressure hull with large exposed areas and rather light connections to the pressure hull constitute a hazard, the elimination of which would make an important improvement in the resistance of a submarine to damage. Future designs will probably incorporate an internal induction line leading directly from a snorkel intake to the engine spaces.

20-14. Close underwater detonations have frequently caused numerous valves in submarines to leak due to rotation of the disc and spindle or distortion of the valve discs or stems. For example, COD (SS224), during her sixth war patrol, reported "During the depth charge attack on 24 April 1945 the first string of charges was of such intensity as to cause the discharge sea and stop valves in the officers' head to open violently; the sea valve operating handwheel was observed to spin rapidly and the stop valve operating lever was thrown to the open position with such force as to shear the pin joining the hand lever to the vertical operating shaft. The stop valve was closed with difficulty, using a wrench." COBIA (SS245) similarly reported that, on 14 May 1945 during her fifth patrol, the water closet valves spun to full open on each of several close detonations. War patrol reports occasionally contain mention of valves which were reported to have opened by as much as three to five full turns as the result of depth charge or bomb attack. In most instances, the opening of valves or leakage due to valve deformation has constituted a nuisance value only. The usual consequences were that full sea pressure was transmitted to internal piping systems, sanitary tanks flooded, inboard vents sprayed water or oil, etc. One of the most frequent damage control measures which submarine personnel were forced to take during attack was the simple task of closing valves which opened. The numerous war patrol reports which mention that valves backed off indicate globe valves were particularly susceptible to rotation and that generally valves throughout the length of the boats were affected rather than those confined to localized areas. The action was not limited to valves exposed to sea pressure for there were many reports where hydraulic and air system valves were affected.

20-15. In a few instances, the chain of events caused by the opening of a valve had serious effects. The following experiences are illustrative:

(a) On 26 October 1944 during her first patrol, ICEFISH (SS367) lost the use of her entire hydraulic system when the 225-pound air supply valve to the hydraulic system vent and replenishing tank jarred open and caused the loss of much of the oil in the system1 This in turn disabled the diving planes and steering until the hydraulic system could be refilled with oil. In addition, a fuel tank inboard vent valve on ICEFISH jarred open in the after battery compartment, causing profuse leakage of oil into that space, and the forward sanitary tank flooded from sea when the discharge line valves opened.


1 See brief of ICEFISH damage in Appendix I

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(b) On 4 November 1944, during her twelfth war patrol, the No. 7 torpedo tube inboard vent valve on SAILFISH (SS192) jarred open as the result of a bomb attack. The large volume of water which entered the after torpedo room through this vent caused the boat to assume a 25 degree up angle and depth control was lost.

(c) On 26 June 1945, during her sixth war patrol, No. 2 sanitary tank on PARCHE (SS384) flooded through the outboard vent which jarred open under attack, and a considerable amount of seawater entered the crews' mess and washroom through the inboard vent of the same tank.

20-16. A program of development and design of explosion resistant valves and locking devices to prevent rotation is currently underway at the Portsmouth Naval Shipyard. One of the features of this program is the actual explosive testing of various valve designs under simulated conditions. It is interesting to note that no large amount of valve rotation has yet been observed as a result of the tests, a 30 degree or one-twelfth full turn rotation being the maximum so far obtained. However, it has been found that deformation of valve stems and discs occurs such that a one-fourth turn of valve handwheels is sometimes necessary to secure tightness after a test. It is of course extremely desirable that valves remain tight during depth charging but the most important requirement is that submarine valves be so designed that although leakage may occur due to deformation or rotation under attack, they will be capable of being made tight again by simply taking up hard on the handwheel.

20-17. In the case of a globe valve, the factors that keep the valve closed under normal conditions are the friction of the thread surfaces in combination with the lead angle of the screw thread, and rotational inertia, the latter being a negligible influence. Under explosive attack, the valve and its supporting structure are set in vibration and it is believed that the friction loads will from time to time be zero or appreciably reduced during the vibrating process. At such a time, it is believed that asymmetrical rotational accelerations can easily make the valve rotate. For example, one way to unscrew an obdurate bolt is to vibrate it while simultaneously applying a torque. In practice, a depth charge attack consists of a series of impulses and the vibrations in submarines are prolonged. One factor which would certainly increase the prospect of rotation of a globe type sea valve would be where the valve disc is deformed by direct pressure pulse loading so that it no longer seats, thus reducing the friction on the threads and rendering it relatively easy for later rotational forces to spin the valve. It is considered that the Portsmouth tests may have failed to produce appreciable valve rotation because the test structure used was more rigid than that of a submarine hull, the test valves may have been initially tightened to a greater degree than would normally be the case with many valves aboard a submarine in actual service, and consecutive explosions were not employed.

20-18. In an effort to reduce the possibility of war damage, various alterations were authorized in order to reduce the number of piping connections passing through the hull and to provide various piping connections subject to sea pressure with both sea and stop valves where such had not been originally installed and war experience indicated to be desirable. Among the many items eventually eliminated on sub-

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marines in service and omitted from the designs for new construction were the following: secondary drainage lines external to the pressure hull; external piping systems penetrating more than one tank; outboard battery exhaust lines; external voice tubes; external conning tower ventilation lines; magnetic compass binnacle tubes; salvage air connections to normal and reserve fuel oil tanks; conning tower flooding line and escape gage sea connections; trim line deck hose connections; various water closet overboard connections; differential gage lines on main ballast tanks; and auxiliary engine exhaust piping. Hull stop valves were provided for the following lines where only sea valves had been previously installed: fuel ballast tank differential gage lines; fuel ballast tank filling and transfer lines; and fuel oil filling connections. The cumulative benefit of these and similar alterations, most of them minor, certainly reduced the vulnerability of our submarines to damage and decreased the number of items to which damage of "nuisance" value was commonly experienced.

20-19. In summing up the lessons learned from war experience with regard to submarine piping systems, the following general observations can be made:

(a) silver-brazed, welded or special union joints and connections should be used wherever possible on all piping where subjected to severe shock loading, both within and without the pressure hull, and even at the expense of increasing the time and cost of repairs;

(b) further development work is required to obtain flanged type joints which will be as shock resistant as silver-brazed, welded or special union joints under war service conditions;

(c) proper sectionalization of vital piping systems to isolate damage, and training of the crew in the use thereof, are of great importance;

(d) the number of hull openings should be held to an absolute minimum;

(e) explosion resistant sea valves and anti-rotational locking devices must be developed;

(f) piping should not penetrate external tank divisional bulkheads;

(g) sea chests or piping leading to sea chests should not be located in fuel tanks;

(h) brackets should not be welded directly to exposed steel piping, as in the case of the induction piping on SCAMP;

(i) the utmost care must be taken in the design, installation and maintenance of piping systems and detail fittings to prevent weak points;

(j) war experience has demonstrated that piping systems on submarines have been more subject to damage, although usually of a nuisance type, than the hull structure, main propulsion plant and principal auxiliary machinery.

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SECTION XXI

HABITABILITY

21-1. Habitability aboard a submarine is a measure of the adequacy of provisions for light, air, humidity, temperature, water, food, rest and recuperation facilities for the crew. In patrol reports submitted by our submarines during World War II, those conditions most frequently commented upon as adversely influencing habitability were: the deficiencies of ventilation and air conditioning while surfaced, submerged or running silent; poor breathing conditions incident to prolonged periods submerged due to accumulation of CO2, depletion of oxygen and increase of air pressure within the boat; the discomfort of cold, wet and rough weather while running surfaced; overcrowding; the inadequacies of water supply and sanitary facilities; the presence of certain noxious or toxic agents such as chlorine gas, carbon tetrachloride, oil fumes, and combustion products incident to fires; and material damage incident to enemy action or accidental flooding.

21-2. In a survey conducted by a representative of the Bureau of Medicine and Surgery of the reports of 1406 war patrols made by fleet type U.S. submarines during World War II, it was found that 658 war patrol reports contained no mention of habitability and conditions on those patrols are therefore presumed to have been fair or better, 106 reported "excellent" habitability, 408 reported "good" habitability, 171 reported "fair" habitability and 63 (4%) reported "poor" habitability. Of the 63 patrols reporting poor habitability, marked inefficiency resulted in only 23 of these due to unfavorable conditions and in only seven patrols was poor habitability in one form or another a deciding factor limiting patrol endurance. Five of these seven patrols were terminated due to contamination or shortage of fresh water and two were terminated due to prolonged conditions of high heat and humidity resulting from lack of air conditioning. Habitability conditions improved notably during the war as new submarines came into service and older submarines were modernized during overhaul periods. After 1942, the percentage of "excellent" reports received was doubled and the percentage of "fair" reports was considerably lowered. During 1943 and 1944 the percentage of reports of "poor" habitability was better than halved and remained at an all time low in 1945. However, the number of reports of only "fair" habitability at no period dropped to an insignificant level, indicating that much room for further improvement exists.

21-3. The program of installation of air conditioning equipment on U.S. submarines, which commenced in the PLUNGER Class in 1936, constituted a major improvement in the military utilization of our submarines for it made possible extended patrols in tropical waters. The principal benefits of air conditioning for submarine use are twofold:

(a) the insulation life of electrical equipment can be greatly lengthened by a reduction in humidity, and casualties due to water condensation or dripping on exposed and energized electrical circuits can be avoided;

(b) comfortable and healthful atmospheric conditions for ship's company can be maintained.

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21-4. There is no more important measure of the habitability of a submarine operating under war conditions than the adequacy of its ventilation and air conditioning systems. Since the earliest installations, the cooling and dehumidifying capacity of air conditioning equipment as installed aboard submarines has been continuously improved, keeping ahead of tremendous increases in crew carried and heat dissipating equipment installed. Frequent casualties during the war were experienced which temporarily disabled the air conditioning systems or, in a few instances, put the equipment out of commission for the major portions of patrols. It is to be noted, however, that U.S. submarines were not only the first to be air conditioned but at the end of the war, virtually the only ones with any significant air conditioning.

21-5. Unfortunately, under war conditions air conditioning and ventilation equipment could not be operated at all times. When conducting an attack approach or employing evasive tactics to escape enemy antisubmarine measures, U. S. submarine operational doctrine calls for the establishment of "silent running". In such circumstances, Commanding Officers usually followed the practice of securing inboard ventilation and air conditioning machinery to achieve minimum noise level, even though this equipment was sound-isolated on many submarines. Lack of air conditioning and ventilation while operating submerged in tropical or semi-tropical waters has almost invariably resulted in high humidity and excessive heat conditions within a very short period of time. Numerous patrol reports have stressed the deleterious effects on personnel of extended periods of silent running and in a few cases the military efficiency of our submarine crews was reported to have been seriously reduced during critical periods. For example, PLUNGER (SS179), while submerged and in contact with the enemy on 1 March 1943 near Makin Island, reported "Noisy air conditioning equipment was shut down as we went in across the bow of the escort. Temperature in the maneuvering room was 130°F. and the engine rooms were about the same . . . men in these two compartments were near prostration from the heat; one man was already receiving treatment. The men on the wheels and planes were being rotated every 5-10 minutes by which time they were totally exhausted . . . Response was slow and acuity dull. Errors were prevalent. It was evident that the ship no longer was in condition to fight or defend itself". PLUNGER thereupon broke off the action without attacking.

21-6. As an example of difficulties encountered when without the benefit of air conditioning during even normal submerged operations, the following excerpts are quoted from TAMBOR's (SS198) second and third patrol reports. "Due to faulty air conditioning units (leaks in Freon piping) the boat was oppressively hot and humid and there was a strong tendency for electrical grounds and short circuits to develop and for finely adjusted contraptions and mechanisms to become inoperative through corrosion. After two weeks of all day submergence all the bunks were wet and stinking. Clothing in the lockers in the forward and after torpedo rooms was green with mildew; practically everyone had a heat rash. There were two cases of heat exhaustion. . . . 30% of the crew developed some type of fungus infection . . . men and some of the officers resorted to sleeping in the torpedo room bilges where it was not quite so hot . . . Lack of air conditioning decidedly had a debilitating effect on the crew and slowed their reactions".

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21-7. During prolonged periods of submergence, further deterioration of the atmosphere has generally been experienced due to excessive accumulation of CO2 and depletion of oxygen. The physiological effects of prolonged exposure to such conditions are well known to submarine personnel. To revitalize depleted air, oxygen replenishment with or without the use of compressed air was commonly employed in conjunction with removal of CO2 by use of chemical absorbents. Foul air together with high humidity and extreme heat due to lack of air conditioning have in several cases seriously reduced the efficiency of our submarine crews. For example, enemy action forced PUFFER (SS268) to remain submerged for 38 hours during her first patrol, the longest known dive made by a U.S. submarine during the war. It was reported that "at the end of 38 hours submerged the men were breathing heavily and almost completely exhausted in spite of all available means being used to purify the air . . . With the air conditioning shut down, the temperature within the boat went to a high figure. A temperature of 125°F. was reported in the maneuvering room. All of the men were nauseated and 75% were vomiting. Both CO2 absorbent and oxygen were used but despite that, the air was very foul towards the end. . . Headaches were severe. A good many men were in a state of physical collapse . . . towards the end, stations were manned by volunteers who had the stamina and will to move and think. Many of the others were past the stage of caring what happened". In PUFFER's case, as in many others, it is impossible to differentiate between the relative deleterious physiological effects of increased CO2, depleted oxygen, increased air pressure, and high humidity and extreme heat caused by lack of air conditioning. Any one of these causes acting alone is sufficient to cause discomfort.

21-8. Before submerging, whenever circumstances permitted, most Commanding Officers followed the practice of thoroughly ventilating their submarines so that the air within at the onset of the dive would be as pure and fresh as possible. In extreme cases, such as PUFFER's prolonged dive, the condition of the ship's atmosphere at the time of diving may be a major factor in determining the maximum possible time of submergence. According to Chapter 38, Bureau of Ships Manual, the established limiting concentrations for minimum safe breathing conditions of 17 per cent oxygen and 3 per cent CO2 will not be reached, assuming fresh air to start with, until the expiration of a period of hours calculated by the following formula T = 0.04 V/N where T is the number of hours, V is the volumetric content of the submarine in cubic feet and N is the total number of men in the crew. By this formula, the limiting values for SS212 and SS285 Class submarines should be reached in about 18 hours. If time spent submerged under ordinary operating conditions is less than the period listed above, oxygen or compressed air replenishment and carbon dioxide purification should normally not be necessary. However, if it is predicted that the time of submergence will be greater than the limiting period, then air purification with CO2 absorbent should be resorted to when the CO2 concentration reaches 2% and oxygen replenishment should be undertaken at the end of the period.

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21-9. Study of some 89 cases of prolonged submergence where foul atmosphere was commented upon and recorded values of the CO2 and oxygen content of the air were reported, indicates that the limiting period of time allowed by the above formula is not always applicable to wartime operations. In 22 of the above reports, the actual limit of viability of the air was from one to six hours less than the calculated figure. Early use of CO2 absorbent should certainly be resorted to whenever long dives can be anticipated. It should be noted that a given weight of the CO2 chemical absorbent will always absorb a given amount of CO2 and that no absorbent can be saved by waiting for high CO2 concentrations.

21-10. An additional factor which often has affected the habitability of submarines operating under war conditions is the increase of internal air pressure usually experienced during prolonged dives due to the cumulative effect of small air system leaks, venting of tanks inboard and firing of torpedoes. Increases in barometric pressure as high as 12 inches (Hg) from these sources were reported in several cases. When not in contact with the enemy, the common practice during the course of a long dive, and often in conjunction with the revitalization of the air supply and use of CO2 absorbent, was to reduce the excessive pressure by pumping air from the ship's atmosphere into the air flasks with the high pressure air compressors. A much more effective measure, however, is to operate the low pressure blower, discharging the air into one or more ballast tanks and thence overboard through the ballast tank vents. Increase in air pressure can be annoying not only from the standpoint of headaches and decreased efficiency induced by the higher than normal pressure alone, but also because some members of the crew may not be able to equalize this pressure within their middle ears and will suffer consequent sharp pain and decreased hearing ability. In addition, increased air pressure will tend to accelerate the poisoning effects of CO2 and whatever other toxic gases may be present.1

21-11. In several cases, toxic or noxious gases have been released in our submarines as a direct or indirect result of war damage. When operating submerged, the military efficiency and even the survival of a submarine can easily be affected by the contamination of the atmosphere with objectionable or deadly gases since these, if present, cannot be ejected. Fires have been the principal source of such gases.2 Chlorine gas formation has been reported in several instances following the introduction of salt water into torpedo batteries or main propulsion batteries. HAMMERHEAD (SS364) on her fourth patrol reported "Battery compartment of torpedo flooded during attack, emitting chlorine gas into boat". PETO (SS265), while submerged and undergoing depth charge attack on her first patrol, detected chlorine gas in the after battery compartment. It was discovered that salt water had been introduced into the main battery from a leaking engine air induction drain and battery ventilation drain which were interconnected. Fortunately, only five cells received a small quantity of salt water and release of chlorine was slight. On GRENADIER's (SS210) fourth patrol,


1 See paragraph 22-15 and TANG narrative, paragraph 10-25.
2 See GRENADIER narrative, Section VIII, and SCAMP narrative, Section IX, for illustrations of the effect of combustion products from fires on personnel and ship operation.

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as the result of a depth charge attack, salt water leaked into the after battery sump from a watercloset that overflowed due to its sea valves jarring open. Sufficient chlorine gas was released from contact of this salt water with the battery acid accumulation in the sump to cause acute discomfort to all hands. Symptoms were aching joints, headaches, pains in throat and lungs, rasping cough, and some cases of vomiting. The efficiency of the whole ship's company was adversely affected for several days. GRENADIER's experience demonstrates the desirability of routine periodic flushing of battery sumps with fresh water and soda lime solution to prevent accumulation of acid. On S-27 and S-36, both of which went aground and were abandoned, salt water entered the battery compartments and chlorine gas was generated.

21-12. In a few instances, fumes from fuel oil leaking into the hull through inboard vents or leaking compensating and transfer lines have caused minor discomfort. For example, TUNNY (SS277), heavily damaged on her seventh patrol, reported "All hands had headaches from breathing oil fumes from the oil leaking into the boat from the No. 7 normal fuel oil tank".

21-13. The type of refrigerant used in air conditioning and refrigerating systems is a matter of much importance on submarines since, on several occasions, depth charge attacks have caused release of refrigerant gas through damaged joints and fittings. Freon 12 is currently employed for air conditioning and refrigerating purposes on U.S. submarines and is ideally suited for such use since it is non-inflammable, non-explosive, odorless and non-toxic in quantities up to 20 per cent by volume. No ill effects were reported in those instances where Freon escaped. An interesting example of what can happen through the use of less suitable refrigerants is the experience of the Dutch submarine HNMS O-19. 0-19 was heavily depth charged on the night of 9 January 1945, while operating under the command of ComSubsSoWesPac during her third war patrol, and was forced to the bottom by the first attack. While still on the bottom, another close depth charge attack was received, one of the most serious effects of which was to cause CO2 to leak from the engine room air conditioning system. The stern compartment and the engine room were immediately evacuated but in spite of closing all bulkhead watertight doors, CO2 reached the control room and made it necessary for personnel to evacuate to the conning tower, the CO2 being heavier than air. The pressure in the boat rose steadily due to internal air leakage from various air systems and accelerated the physiological effect of the CO2 on personnel. Escape breathing equipment (Draeger), fitted with soda lime containers, was used to absorb excessive CO2 content in areas of dangerous concentration. The telephones were out of action and personnel in the various compartments had no way of ascertaining what was going on in the other spaces. Two hours later, the boat was surfaced with the engine room still secured but was immediately placed on the bottom again when two enemy vessels were sighted close aboard. It was then decided to re-enter the engine room while submerged, ready the engines and then attempt to escape at high speed on the surface. A small party of men using rescue breathing equipment (DSEA) managed to enter the engine room and rig the engines for immediate starting. The engine room was found half flooded, the leakage

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occurring through sea valves which had jarred open during the last depth charge attack. Some men who removed their DSEA sets in order to reach valves located in confined areas were overcome by the CO2 All of the men in this party suffered after effects to some extent from CO2 poisoning. The ship was then surfaced and escaped without difficulty, the enemy having departed. Repairs were undertaken at Fremantle, W.A., at which time the air conditioning plant was converted for use with Freon gas.

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SECTION XXII

SUBMARINE ESCAPE NOTES

22-1. The problem of escape and rescue of personnel from sunken disabled submarines is currently undergoing review and study by the Navy Department. As projected submarines will be capable of operating at depths greatly in excess of 500 feet, it is evident that currently available escape devices, rescue chambers, search aids, and doctrine for their proper use, must be reconsidered as to their applicability for use at such depths. This is particularly apropos in view of the tragic war experience of TANG (SS306) where only six of some forty men were able to escape from underwater although the submarine was sunk in only 180 foot depth.1 It has become apparent that new devices and techniques must be developed before escapes from submarines disabled at relatively great depths will be feasible.

22-2 There are at present but three accepted methods considered practicable for our submarine service by means of which personnel can successfully transit from a sunken disabled submarine through the intervening water layer to the surface. The first and most obvious method is based on rescue by the use of a structural chamber designed to withstand hydrostatic pressure throughout its operating depth and which can be brought down from the surface to specially designed hatch openings on the disabled submarine below, enabling relatively safe group escapes. This instrument was developed by the U.S. Navy and is known as the "submarine rescue chamber". The second method calls for individual escape, personnel exiting from the disabled submarine through either a small intermediate enclosed air-lock or a skirted-type trunk built into the pressure hull, and then slowly ascending to the surface with the aid of a mechanical breathing device known in the U.S. Navy as the "lung". Rate of rise to the surface of the escaping personnel using this second method is regulated by ascending a line secured from the submarine to a surface buoy. An escape breathing apparatus has been used by all major navies and in the U.S. Navy a certain amount of "lung" training under simulated escape conditions is normally a mandatory requisite for all submarine service candidates. The third method may at the present time be considered an emergency variation of the second method. Individual escape is made through the same air-lock or trunk as in the second method but ascent to the surface is "free"; i.e., a rapid ascent is made without the use of mechanical breathing aids or ascending line of any nature, escaping personnel rising under the influence of their own buoyancy and swimming up. Although some instruction is given in this method of escape in the U.S. Navy, it has so far not been particularly emphasized or recommended and "free" training ascents have not been required due to preference for the "lung" escape and the probable training hazards involved in "free" escapes where large numbers of men are involved.

22-3. The escape problem on submarines is considerably increased by the necessity of having to confine escape structures and equipment


1 See TANG narrative, Section X.

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to those consistent with the required military characteristics of the ship. Space and weight considerations usually render it extremely difficult to achieve even the minimum desired military features on a new submarine design. Escape provisions are therefore naturally given secondary emphasis. Many workable schemes which would be decided improvements over existing escape arrangements could be devised if a submarine had no military mission. One such ideal but inadmissible proposal would be to design a portion or portions of the hull which could be detached and brought to the surface by the surviving members of the crew.

22-4. In the entire history of the U.S. Navy there are only two known instances of successful underwater escapes from sunken disabled submarines. SQUALUS (SS192) sank off the Isles of Shoals in 230 feet of water on 23 May 1939, when all compartments aft of the control room flooded through the engine air induction piping. The next day all of the 33 men who survived the initial flooding were removed through the forward torpedo room escape trunk by expeditious and skillful use of a submarine rescue chamber. The task was accomplished in four trips. TANG (SS306) was sunk off the coast of China in 180 feet of water on 26 October 1944 by the malfunctioning of one of her own torpedoes. Six men made successful individual escapes from underwater, one from the conning tower and five from the forward torpedo room escape trunk. The conning tower escape and one of the forward torpedo room escapes were "free". The remaining four were "lung" escapes. At least eight other men are known to have left the escape trunk but either died shortly after reaching the surface or were not seen again after leaving the trunk.

22-5. Since the experience of the U.S. Navy with underwater escapes, other than training exercises, is limited to the above two cases, it is necessary to turn to the experiences of other nations for further data. The British Admiralty Submarine Escape Committee has compiled information and statistics on every instance known to them of past submarine escapes of all countries. These records contain much interesting, and in some cases, detailed information. They serve to stress the difficult conditions usually attendant upon submarine escapes after damage and which in most instances have prevented a high percentage of successful escape completions. The escape problem on submarines can be considered in three phases as follows: (1) survival within the submarine after damage up to the time personnel actually exit from the hull, (2) survival during the ascent to the surface and (3) survival after reaching the surface until rescued.

22-6. According to the British records, of all the personnel who have been carried to the bottom in known cases of sunken submarines, a total of about 500 men are believed to have survived both the initial accident or damage causing the sinking and the subsequent primary flooding. Of these 500 men, a total of 32 were rescued from three submarines of such small size that the boats were lifted bodily by cranes;1


1 U-3, 18 January 1911; USS O-5, 29 October 1923; HDMS DYKKEREN, 10 October 1916.

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33 were saved by rescue chamber;1 and 46 were taken off a submarine sunk in shallow landlocked waters where raising the bow of the ship was comparatively simple and expeditious.2 Of the remaining 390 men who survived the initial accident, approximately 250 or 60% perished inside their respective submarines. It is probable that the principal cause of the majority of these deaths was CO2 poisoning, in some cases due to delaying the escape attempt too long,3 and in others to the accelerated poisoning effect of CO2 when present in atmosphere under high pressure.4 This latter condition occurs when flooding a compartment to equalize internal pressure with sea pressure to permit a skirted-trunk escape. Other known causes were drowning due to further uncontrollable or inadvertent flooding,5 drowning as a result of deliberately flooding a compartment to equalize internal pressure with sea pressure to permit skirted-trunk escapes,6 chlorine gas,7 and drowning within an air-lock type escape trunk.8 Of the 142 men who are known to have left their submarines on attempted individual escapes, 106 men or 75% reached the surface alive and survived until rescued. This represents only 27% survivors of the possible original 390. Of the 36 who left their ships on attempted escapes but did not survive, some are known to have reached the surface alive but subsequently died by drowning, exhaustion, or by prolonged immersion in cold water.9 The others died from various causes, among them being air embolism, asphyxiation, ruptured lung tissue due to failure to exhale during ascent, and drowning due to inhalation of water during ascent.

22-7. The statistics for these escapes, although not based on enough instances to be conclusive, indicate the following interesting and pertinent points:

(a) It appears that with present equipment and techniques the chance of survival by using the individual escape method decreases about 10% for every 30-foot increase in depth, until at 250 feet and beyond, the chance of survival is very small.

(b) The phase between the initial accident and the actual escape attempts is by far the most critical. Eighty-eight per cent of all subsequent deaths among personnel who survived the initial accident occurred during this period.


1 USS SQUALUS, 23 May 1939.
2 HMS K-13, 29 January 1917.
3 HMS THETIS, 1 June 1939, 95 men; U-51, World War I, 16 men; U-741 World War II, number unknown.
4 HMS UNTAMED, 30 May 1943, 36 men.
5 UB-57, World War I, number unknown; HMS STRATAGEN, November 1944, possibly 4 men.
6 U-767, World War II, 6 men.
7 U-859, World War II, 4 men.
8 HMS THETIS, 1 June 1939, 4 men.
9 Four 7-man CO2 inflated life rafts will be furnished to each active submarine as soon as available and the hull allowance lists have been modified accordingly. SEA FOX (SS402) conducted tests which demonstrated the practicability of ejecting such rafts from torpedo tubes, using torpedo impulse air. It is expected that deaths due to exposure and drowning subsequent to reaching the surface should be reduced by successful use of these rafts in conjunction with escape operations.

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(c) The advantage of rapid flooding over slow flooding when sea water must be admitted to a compartment to equalize internal air pressure with external sea pressure to permit escape through a skirted-trunk, is demonstrated by the fact that there were only 21% survivors after slow flooding whereas 66% survived when flooding was rapid. As would be expected, the figures also show that as the depth increases, a higher percentage of survivors results when the escape compartments are flooded rapidly rather than slowly. This is particularly marked at depths greater than 100 feet.

(d) The hazard of the ascent itself, particularly when made by well trained personnel, is relatively minor for depths up to about 200 feet. Of all the men who left their submarines on individual escape attempts, either with or without an apparatus, probably less than 10% perished during the actual ascent.

(e) Well over half of the survivors made "free" ascents, either entirely without breathing apparatus or with such apparatus but using it as a buoyancy bag only due to maloperation or defective parts.

22-8. When circumstances permit use of a submarine rescue chamber, this method is usually to be preferred since it is likely that a higher percentage of successful rescues will be obtained and no individual effort is required on the part of the men trapped within the sunken submarine. However, the following conditions must exist:

(a) The fact that the submarine has sunk must be made known to cognizant rescue authorities within a short period after the sinking occurs.

(b) Its exact position on the bottom must be definitely established.

(c) The depth of water must not exceed the operating depth of the rescue chamber, or with present apparatus, the depth at which divers can descend to attach a downhaul cable.

(d) A rescue chamber, trained crew and rescue vessel must be so located as to reach the scene quickly.

(e) Tides, currents and weather must be favorable for diving and rescue chamber operations.

(f) The survivors within the submarine must be able to reach an escape station fitted for use of the rescue chamber.

(g) List and trim of the submarine as it lies on the bottom must be such as to permit proper access to the escape station attaching surface.

In time of war, conditions (a), (b) and (d) will usually not be met.

22-9. Presently available rescue chambers and operating gear are not considered suitable for rescue of submarine personnel at depths much exceeding 450 feet. This is due to the fact that, although the

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structural design of the latest chambers provides for a rated operating depth of 550 feet, divers must attach the chamber downhaul cable to the submarine and 450 feet is considered to be about the maximum possible working depth of divers using present diving techniques under ideal conditions. Development is currently underway on a proposed submarine messenger buoy which when released from a sunken submarine will float a light high strength rescue chamber downhaul cable from depths as great as 850 feet. Investigation shows that the present rescue chambers can be altered for use at 850 feet with but minor modifications. This scheme will eliminate the use of divers and the need for complicated mooring of the rescue vessel.

22-10. When use of the rescue chamber is not feasible, due to any of the conditions enumerated in paragraph 22-8 above, the only hope of survival for the crew members will then lie in individual escape attempts. The submarine escape device or "lung" was developed by the U. S. Navy in 1929 to provide individual crew members with a reasonably safe means of escape from disabled sunken submarines. An extensive program of indoctrination and training of submarine personnel in its use, capabilities and limitations was undertaken. In order to provide "lung" training at substantial depths, escape training tanks were constructed at the U.S. Naval Submarine Bases at New London and Pearl Harbor in 1930 and 1932, respectively. These towers have an overall height of 134 feet providing a vertical column of water 100 feet high and 18 feet in diameter with escape locks or compartments simulating those on submarines located 18, 50 and 100 feet from the top of the tank. This permits escape training under conditions approximating those existing in similar depths at sea and with identical pressure factors. With the advent of World War II the program was expanded tremendously in an effort to provide "lung" instruction for all men training for the submarine service, although a considerable number of men unfortunately did not have access to such training. Since inception of the program, over 46,500 men have made the 18-foot ascent, over 29,800" men have made the 50-foot ascent and over 6,300 men have made the 100-foot ascent.

22-11. A study of TANG's experience, where only 5 men or 10% of a possible 45 men trapped in the forward torpedo room successfully escaped, indicates that an increase in the speed of operation of the trunk would have enable more personnel to make the attempt. The average time between successive escape parties was from 45 minutes to one hour. This compares very unfavorably with recent shallow water escape exercises conducted by SIRAGO (SS485) on 28 and 29 August 1946. The submarine was submerged to a keel depth of about 70 feet and a total of 35 officers and men made individual escapes through the forward torpedo room air-lock, entering the trunk in groups of

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3 and 4. The average time for each escape cycle, i.e., the time required for each party to enter the trunk, flood, escape, and for subsequent draining and readying of the trunk for the next party, was about 15 minutes. The minimum cycle time was 9 minutes and the maximum 26 minutes, this latter time including rigging of an escape buoy, ascending line, and streaming of a Mark 4 rubber boat from the escape trunk. During these exercises three men experienced difficulty with their "lungs". One who had had previous instruction in "free" escape made the ascent successfully without his "lung". The other two returned to the trunk.

22-12. The need for continued and rigorous "lung" escape instruction for all men and officers of the active submarine service, including periodic refresher courses, is clearly indicated if reliance is to be placed on this method in the future. In addition, more emphasis should be placed on the "free" escape method. Familiarity with this type of escape certainly holds the possibility of saving lives in many conceivable instances and will in addition induce more confidence in the "lung" type of escape.

22-13. It is pertinent to consider whether or not more lives would have been saved on TANG had the forward torpedo room been fitted with a skirted trunk, as in the after torpedo room, instead of the air-lock type escape trunk. In TANG's case there are certain advantages which could be claimed for either type due to the fact that the depth of 180 feet was only slightly in excess of that beyond which the skirted trunk is ordinarily not considered suitable.

22-14. The principal advantage of the skirted trunk is that once the escape compartment has been flooded so as to equalize internal air pressure with sea pressure, and the trunk outer hatch has been opened, individual escapes can then proceed in rapid succession with but a few seconds interval between departures. The technique is simple and requires but little effort. All personnel know what is going on at all times. If a man happens to "freeze" in the trunk he can immediately either be forcibly ejected or drawn back into the compartment. This procedure would have eliminated the long delays between successive escape parties which were so disastrous for TANG and it is quite possible that more men would have been forced to make the escape attempt and therefore more would have reached the surface alive.

22-15. The principal disadvantages of the skirted trunk for escape at great depths are as follows:

(a) During and after the period of flooding the escape compartment to equalize internal pressure with the sea, personnel within will be subject to nitrogen narcosis, CO2 poisoning, and the deleterious effects of other noxious or toxic gases which may be present, such as chlorine, carbon monoxide, smoke, etc., since these gaseous components will be under higher than normal pressures. For example, the concentration of CO2 which can be tolerated is inversely proportional to the absolute pressure; at an air pressure equivalent to 350 foot depth of water, three per cent CO2 content by volume, which would be harmless at atmospheric

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pressure, will have about the same physiological effect as thirty per cent CO2 content by volume at atmospheric pressure and will cause death in a very short period of time. Approximately the same holds true for nitrogen and noxious or toxic gases. At pressures corresponding to depths greater than 150 feet, this effect may become so pronounced that personnel can remain conscious only for very limited periods of time, particularly if the atmosphere initially contains smoke, toxic gases or higher than normal portions of CO2. Increasing the percentage of oxygen in the air may also introduce the possibility of oxygen poisoning at high pressures.


(b) Breathing air at high pressure will render an escaping man susceptible to air embolism and caisson disease ("bends"), particularly if ascent is rapid as in the "free" escape method. At 300 foot depth, for example, a man could not safely make a "free" ascent after breathing air at the equivalent pressure for more than about three minutes, and for an even shorter time if he has already been subjected to a flooding period during which air pressure was raised gradually.

(c) Unavoidable immersion of personnel in cold water during the flooding period may cause deaths by drowning or exposure prior to the escape attempt.

These factors are considered to render the skirted-type trunk useless for escape at depths much below 150 feet for the average person, although from a standpoint of simplicity there is much to be said in its favor. The principal and very great advantage of the air-lock type escape trunk is that it enables rapid compression of the escape party to sea pressure and permits remaining personnel within the ship to stay at pressure near normal while awaiting their turn.

22-16. In considering problems involved in the successful execution of individual escapes, the debilitating effect on mind and body of some or all of the following possible conditions must constantly be borne in mind:

(a) The shock effect on personnel of the initial accident or damage which caused the sinking.

(b) The presence of seriously injured or mentally deranged personnel.

(c) Lack of lighting.

(d) Exposure to heat or cold and excessive humidity.

(e) Continued breathing of poor or toxic atmosphere.

(f) Excessive trim or list on the submarine which may render even normal movements difficult.

22-17. It is clearly evident in the light of available experience that the first requirement of any escape method is that it be simple and so calculated as to obtain the highest percentage of survivors. It is also apparent that present methods are not satisfactory at deep depths.

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22-18. The British are currently investigating the use of a small cylindrical one-man escape chamber fitted with hatches top and bottom and provided with a mechanical apparatus permitting forced ejection of a man from within the trunk if necessary. This trunk would be intended for use in conjunction with both "free" and "lung" escapes. The system is believed by the British to have the following advantages:

(a) Simplicity.

(b) The escaping man has no control over the operation once he enters the trunk, and whether dead, unconscious or confused, he can be forcibly ejected to make room for the next man.

(c) A total trunk operation cycle time of about 4 or 5 minutes appears possible.

(d) Brief subjection to air at high pressure minimizes the chance of nitrogen narcosis, CO2 poisoning, air embolism and caisson disease.

22-19. In this country, as stated previously, further research and development studies are underway by the Navy Department in an effort to improve submarine search and rescue equipment. One line of investigation which may prove of great value is the use of helium-oxygen mixtures in conjunction with a breathing device and which possibly may permit use of the skirted-type trunk for escape at all depths up to the collapse depth of the submarine itself. The "flooding up" stage, which is a necessary preliminary to a skirted-trunk escape, is particularly critical due to the inability of average individuals to remain conscious for even short periods when breathing a normally proportioned air mixture at high pressure. For example, it is considered likely that if an escape compartment were slowly flooded at a depth of 350 feet, most normal personnel within would be incapacitated or unconscious before internal pressure had been equalized with sea pressure. It has been determined that the air component chiefly responsible for unconsciousness when breathing under high pressure is the nitrogen portion. When the nitrogen is replaced by helium, unconsciousness does not occur at least up to 500 feet and there is reason to believe that unconsciousness will not occur at depths considerably greater than 500 feet inasmuch as the intoxication preceding coma does not occur to any extent even at 500 feet when using helium. From a physiological point of view, the "lung" itself is believed to be capable of permitting safe ascent from depths considerably greater than 500 feet, providing the proper breathing mixtures can be continuously provided and decompression rules are carried out.1 Divers using helium-oxygen mixtures, for example, have worked


1 "Lungs" have been used with normal air mixtures at simulated depths as high as 354 feet in the mine tank of the U.S. Naval Gun Factory, Washington, D.C. Actual escapes were made in the open sea off Key West, Florida, at depths up to 200 feet from the torpedo room and motor room of S-4 (BuC&R ltr. No. L9/P-(14) (ME)N/C; EN7/A2-11 of 10 September 1929);

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at a depth of 440 feet in conventional diving suits.1 Initial inflation of "lungs" with helium-oxygen mixtures would also facilitate and may even be mandatory for air-lock escapes at extreme depths. The depth limitation of the present "lung" for individual escape, using oxygen alone, is considered to be about 200 feet for normal men, and it is believed that helium-oxygen mixtures should be used at all depths greater than 200 feet.2

22-20. Other projects which are currently being investigated and which may prove of practical value for locating sunken submarines and for escape therefrom are:

(a) Development of a radio beacon which can be ejected from a signal ejector on a sunken submarine to give automatic distress warning signals useful for homing by searching vessels.

(b) Development of a noise source, such as a sonar test target with increased power, suitable for sonar homing.

(c) Dye markers which can be ejected from a signal ejector to indicate location.

(d) Development of a short range emergency-powered underwater sonar telephone system which can be used for communications during rescue operations.

(e) Development of a messenger buoy and modification of present rescue chambers for operations at great depths, as mentioned in paragraph 22-9.

(f) Modification of the "lung" to provide a collar for buoyant support of the head after reaching the surface (similar to German apparatus), in order to lessen the chance of drowning if the wearer becomes unconscious after surfacing.

(g) Provision of equipment for mooring submarine rescue vessels in 850 feet of water.

(h) Development of a simple battery-powered two-way voice communication system between the escape trunk and compartment below. The experiences of TANG (SS306) and SIRAGO (SS485) demonstrated the inadequacy of attempting communications by hammer taps or other such means.

(i) Experimental investigations in "free" escape techniques.


1 U.S. Navy divers reached 440 foot depth without suffering adverse effects while inspecting 0-9, lost with all hands on 20 June 1941 off the Isles of Shoals. A 90/10 helium-oxygen mixture was used.
2 Helium-oxygen mixtures can be quite easily provided for submarine bow and stern compartments in a manner similar to that now used for oxygen stowage.

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SECTION XXIII

CONCLUSION

23-1. In World War II the capacity of our submarines to survive intense underwater explosive attacks without receiving damage of serious nature was clearly established and continuously increased during the course of the war. This was accomplished principally by instituting a comprehensive shock protection program for all submarines in service and under construction and by increasing the scantlings of the pressure hulls on more recent classes to permit greater operating depths.

23-2. The damage experiences of KING FISH, TUNNY, SALMON, SCAMP, HALIBUT and REDFISH represent instances where considerable permanent pressure hull deformation was sustained by submarines on which all or a substantial portion of the shock protection program had been accomplished. On these vessels, vital equipment was in general not affected seriously although further improvement in the resistance to damage of certain components, particularly piping and electrical items, was clearly indicated.

23-3. From the standpoint of vulnerability to non-contact underwater explosive attack, the ideal submarine is one having a pressure hull of maximum efficiency for the allowable weight of the shell and framing, free of stress raisers, and with all other equipment, appurtenances, systems, etc., of such strength or so well protected from shock that the hull itself will be destroyed before other vital components sustain serious damage. In other words, the ideal submarine could only be destroyed by causing collapse or holing of its pressure hull. This desirable condition has been closely approached on modern U.S. submarines. It is significant to note that only five reports in the entire Japanese list of 468 "positive" sinkings of U.S. submarines referred to in Appendix II mention partial or complete surfacing of a submarine having occurred while it was under attack, none of which can be related to a known sinking, whereas over 200 reports contain mention of sighting large quantities of oil, frequently accompanied by air bubbles and debris, after attacking purported submarines. These figures, although admittedly based on incomplete information, would seem to indicate that destruction of our submarines occurred through rupture of their pressure hulls since it is reasonable to assume that even though a submarine were disabled so that it could no longer operate submerged, sufficient air should remain to permit surfacing.

23-4. In the final analysis, it is apparent that the survival of many of our submarines after receiving war damage was due in very large part to the damage control efforts of their personnel. The long standing requirement that all hands in the submarine service know their ships thoroughly has paid priceless dividends in terms of human life and the successful prosecution of the war.

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23-5. As a result of the great improvements made in anti-submarine warfare during the past few years and prospective radically new developments in propulsion machinery, the concept of the submarine of the foreseeable future has undergone drastic change. U.S. submarines as developed for World War II were designed primarily for employment as submersible surface raiders with high surface speed and low submerged speed. This type of submarine was remarkably successful in operations against the Japanese and fortunately suffered a relatively low rate of attrition due to the marked ineffectiveness of the enemy anti-submarine effort. The present trend of U.S. submarine design is in the direction of smaller, high submerged speed attack submarines capable of operating at extreme depths. Other types of submarines for special missions are also under consideration. With the advent of a suitable propulsion plant capable of delivering great power for sustained operations submerged, the submarine will become a true submersible.

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APPENDIX I

Briefs of War Damage Incurred by U.S. Submarines

During World War II

1. A survey of war patrol reports and other information available to the Bureau indicates that during World War II there were 110 separate instances in which United States fleet type submarines survived damage from attack by either enemy or friendly forces where the damage received may be considered as more than negligible or where the circumstances of the attack or the nature of the damage has been considered of sufficient interest to warrant reporting. Briefs of each of these damage cases are presented on the following pages of this Appendix. Receipt of information with substantiating documents in correction of any of the data which may be found in error will be appreciated. Address Code 424, Bureau of Ships.

2. This Appendix together with Appendix II, the latter being a tabulation of United States submarine losses, summarize presently available information on the war damage experiences of U.S. Navy submarines throughout World War II. Section II contains a statistical summary of the types of weapons causing the damage in the 110 separate instances of damage, and a list of the governing damage item or items which forced termination of 49 war patrols.

3. Seven of the 110 damage cases listed in this Appendix have been described in detail in the body of this report.

4. Appendix I and Appendix II supplement the series of four confidential publications prepared by this Bureau which summarize the war damage to U.S. battleships, carriers, cruisers and destroyers for each of the four years of the war.

5. The following briefs have been arranged in as close adherence to chronological order as could be made without continuing the "remarks" column of any brief to another page.

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NAME

DATE

PLACE

SOURCE

REMARKS

SEADRAGON (SS194)

12/10/41

Navy Yard, Cavite, P.I.

Bombs - 2

SEADRAGON was berthed inboard of SEALION (SS195) at Navy Yard, Cavite during Japanese high level bombing attack. Fragments from two small bombs which made direct hits on SEALION, one amidships and one aft, caused considerable structural damage on SEADRAGON. Conning tower was holed in four places, varying in size from 3 to 6 inches in diameter. Most of bridge and conning tower wiring was carried away or punctured. Conning tower deadlight, port side, was blown out. Radio antenna trunk was torn open. NFO No. 1 and MBT No. 3F were punctured by many small fragments. One large fragment caused dent about 6 inches deep at frame 155 and slight tear in pressure hull plating. Superstructure plating amidships and conning tower fairwater were riddled in numerous places. Engine air induction piping was punctured over after engine room. Open paint pots on deck ignited, causing fire damage topside.

SARGO (SS188)

(3rd)

Off Western Australia
About 30°S. 113°E.

Bombs - 2

Received two bombs from RAAF two-engined bomber. First bomb was received shortly after diving, causing no damage but forcing ship to assume large down angle. Descent was checked at 170 foot depth by stopping motors and blowing bow buoyancy and forward group of main ballast tanks. Ship then broached and received second bomb close aboard conning tower while at about 50 foot depth. Main propulsion power was temporarily lost for reasons not stated. Both periscope exit windows and prisms were shattered and both periscope tubes flooded. After bulkhead of conning tower was slightly deformed, causing after bulkhead door to leak seriously at depths above 80 feet. Electrical panels and engine order telegraphs in conning tower were grounded by flooding. Three porcelain water closet bowls fractured. High pressure air system developed two leaks. Lighting power was lost and numerous bulbs were broken. Many gauges meters and instruments were deranged or broken and other minor damage occurred. Ship was already enroute to base but otherwise would have had to terminate her patrol due to periscope damage.

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NAME

DATE

PLACE

SOURCE

REMARKS

PERMIT (SS178)

3/17/42
(4th)

Tayabas Bay, P.I.
(Lat. & Long. not reported)

Depth Charges - 14

Depth charged by three Japanese destroyers shortly after submerging and on way deep. Conning tower door gasket was cut by excessive pressure on knife edge of door seat and partially bulged out, resulting in considerable leakage into conning tower. Other damage was minor. Ship remained on patrol.

SEAWOLF (SS197)

3/31/42
(4th)

Off Christmas Island, Indian Ocean
10° - 26' S.
105° - 41' E.

Depth Charges - 25

Depth charged by Japanese destroyers and/or cruisers over 7 1/2 hour period. First attack tripped overload relays on after battery negative bus. This caused main power bus contactor and main battery bus contactor to open, cutting off power to main motors. Ship dropped from 200 to 270 foot depth before power was restored. Relays and contactors were then blocked closed with wooden wedges. Engine lube oil cooler coils developed leak, allowing sea water to enter main engine sumps since circulating water sea valves were not tight. Gyrocompass repeaters and radio transmitters were disabled. Cable stuffing glands in conning tower and starboard shaft stern tube leaked heavily. Trim line ruptured in forward torpedo room, and as emergency measure, forward trim tank was blown and flooded through torpedo tube drain and vent valves. Ship remained on patrol.

PORPOISE (SS172)

5/8/42
(3rd)

Off Ceram, Moluccas
3° - 50'S.
129° - 57'E.

Depth Charges - 4

Depth charged by Japanese escort while at 170 foot depth. Stern planes lost power and jammed temporarily. Hull valve to NFO No. 3 backed off and relief valve in after torpedo room opened, admitting fuel oil to that compartment. Elbow in blow line to NFO No. 3 was ruptured. Two battery jars cracked. Ship remained on patrol.

GRAMPUS (SS207)

5/17/42
(2nd)

Off Truk
08°-02'N.
151°-30'E.

Gunfire - 1
(3 or 4.7 inch)

Received one 3 or 4.7 inch shell hit in after portion of conning tower fairwater. See Section XII for detailed account. Ship remained on patrol.

--252--


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REMARKS

NAUTILUS (SS168)

6/28/42
(1st)

Off Central Honshu
35°-54'N.° 140°-13'E.

Depth Charges - 11

Depth charged by Japanese cruiser. Five close charges were received while passing 200 foot depth on way down. Rudder operation became very noisy as result of depth charging and starboard ram moved in jerks, either due to air in hydraulic system or jammed packing. Three pressure hull hard patches developed leaks. Bow plane indicator housing in anchor windlass room fractured. Electrical cables were forced into hull and in several cases streams of water entered hull around packing glands. Silver-soldered joints of Nos. 4 and 10 high pressure air banks developed leaks. Silver-soldered joints in hydraulic line to No. 7 MBT parted and several other hydraulic lines leaked. Both stern tube stuffing boxes developed excessive leakage. Outboard main engine exhaust valves leaked, allowing external exhaust piping to flood. Plastic coating in variable tanks flaked loose and particles appeared in forward torpedo tubes from WRT tank. Miscellaneous other minor damage occurred. Ship remained on patrol.

THRESHER (SS200)

7/9/42
(4th)

Off Kwajaleln

Bomb - 1

Bombed by unidentified Japanese aircraft while passing 80 foot depth. Serious air leakage developed at high pressure air bank in No. 5 MBT. Main vent valves had been left open and consequently air bubbled to the surface through vent riser, enabling enemy planes and surface escorts to track THRESHER, the sea being glassy calm. Several more bomb and depth charge attacks were made but resulting damage was minor. Ship was also hooked by small grapnel for ten minutes. Ship remained on patrol.

PICKEREL (SS177)

8/12/42
(5th)

Off Marianas Islands
16°-19!N.
145°-23'E.

Depth Charges - 4

Depth charged by Japanese escort while at 230 foot depth. Tubes in Nos. 1 and 2 main engine heat exchangers were ruptured. Cooling water hose to No. 2 main engine outboard exhaust valve carried away. Hull stop valve for hose line was secured but not until spray had entered No. 2 main generator casing through flexible coupling and soaked field windings. Fresh water rinse and slow drying by application of heat restored generator to service. Ship remained on patrol.

--253--


NAME

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SOURCE

REMARKS

FLYING PISH (SS229)

9/2/42
(2nd)

Off Truk
7°-46'N.
151°-57'E.

Depth Charges - 8

Depth charged by Japanese PC. Received three charges while passing 160 foot depth and 5 charges while at 250 foot depth. Unstated damage caused leakage into after trim tank of 8000 lbs. hourly at 300 foot depth. Stern planes were forced out of alignment, requiring two men to operate them with difficulty by hand power. Cables on No. 1 periscope parted. This periscope was housed at limit switch and dropped 4 inches to bumper. Engine air induction piping and forward battery soft patch leaked. Boat was unable to maintain satisfactory trim or run silent. Patrol was terminated.

SCULPIN (SS191)

9/28/42
(5th)

Off New Britain
3°-47' S.
151°-36'E.

Depth Charges

(No. not reported)

Depth charged by two Japanese escorts while at about 250 foot depth. First close charges caused temporary loss of main power by jarring control cubicle overload relays open. These were reset by hand and power was regained ten seconds later. Stern planes lost power and stalled on 15° dive position with boat at 280 foot depth. By quickly shifting to hand control, the planes were operated again before serious effects on depth control resulted. Contact arm porcelain insulator in governor control for No. 1 generator engine fractured, causing full ground on generator armature circuit. Various leaks throughout boat caused increase of 20,000 lbs. weight. Maintained depth by running at 2/5 speed ahead on both shafts with 10° to 12° rise angle on boat. Gauge glass on hydraulic replenishing tank fractured, causing loss of oil in tank. Knife edge on conning tower door seat cut through door gasket but only minor leakage resulted. Refrigerating compressor motor in pump room flooded out, causing loss of all stores In cold room. Numerous valves jarred open, gauges shattered, light bulbs and fixtures broke and miscellaneous other items of minor damage occurred. Temporary repairs were made and ship remained on patrol.

TROUT (SS202)

10/5/42
(5th)

Off Truk
(lat. & long. not reported)

Bomb - 2

Received bomb from Japanese aircraft while at 58 foot depth just as periscope was being lowered. Second bomb was received shortly thereafter while passing 80 foot depth on way down. Both Nos. 1 and 2 periscopes were put out of commission. The upper windows were shattered, upper prisms cracked, control wires jammed and periscope tubes flooded. No other damage was reported. Patrol was terminated due to periscope casualty.

--254--


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REMARKS

NAUTILUS

(SS168)

10/12/42
(3rd)

Off Northern Honshu
41°-05'N.
141°-58'E.

Depth Charges - 15

Depth charged by AMAGIRI Class Japanese Destroyer. Majority of damage sustained was from one pattern of 5 charges dropped close overhead while NAUTILUS was running at 250 foot depth. Threaded high pressure air piping connection at forward separator started to leak. Rudder post packing jammed, causing rudder to groan and seize. Torpedo tubes Nos. 8 and 10 flooded through muzzle door gaskets. Impulse air system for deck tube No. 8 developed external air leak to sea. Bellows on pitometer log ruptured. Leak developed between NFO No. 5 and FBT No. 4B. Water seal gaskets on 6-inch deck gun were crushed. Bow plane tilting shaft clutch disengaged three times on close charges. No. 3 main Diesel engine governor jammed and engine had to be run by hand control for four hours. Port main motor bearing oil seal packing jarred loose, allowing oil to leak. Contacts for No. 1 lighting motor generator and port main motor ventilation blower jarred closed, starting both units. Optical systems of both periscopes were deranged. Ship's supply ventilation inboard hull flapper valve was misaligned, causing difficult operation. Numerous gauges, meters, instruments, etc., were broken or deranged and other minor damage occurred. Ship remained on patrol.

WHALE (SS239)

10/30/42
(1st)

Off Southern Honshu
33°-34'N.
135 -15'E.

Depth Charges
(No. not reported)

Depth charged by Japanese OTORI Class torpedo boat. First close charges were received while passing 150 foot depth. Boat then leveled off at 300 foot depth but engine air induction, ship's supply ventilation and battery outboard exhaust piping topside completely flooded, causing increase in weight overall and aft. Inboard induction flapper valve in engine room was distorted and leaked badly. Boat assumed 15 up angle and started to settle. Up angle was reduced to 5° by sending 50 men to forward torpedo room. Depth control was regained at 360 feet and maintained thereafter by occasionally increasing speed and by blowing after trim to sea. These actions enabled the enemy to retain contact and depth charging by their escorts and and planes continued at various intervals for three hours. Motor room bilges flooded from excessive leak through starboard shaft stern tube packing. Starboard shaft developed pronounced swishing and squealing above 95 rpm, indicating misalignment. Other minor damage occurred. Patrol was terminated.

--255--


NAME

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SOURCE

REMARKS

GRAYLING (SS209)

11/6/42
(4th)

Off Truk
6°-44'N.
151°-25'E.

Bombs - 3

Bombed by unidentified Japanese aircraft while at periscope depth. High pressure air piping developed leaks in after battery well and after torpedo room. Radio antenna trunk flooded and all antennae were knocked down. No. 2 periscope optical system was deranged. Gaskets on MBT Nos. 5A and 5B spring loaded vent valves were dislodged. Miscellaneous other minor damage occurred. Ship remained on patrol.

TAUTOG (SS199)

11/11/42
(4th)

Makassar Strait
1°-22'N.
119°-31'E.

Depth Charges - 11

Depth charged by Japanese escort while at about 250 foot depth. Cast iron plug in auxiliary engine circulating water sea valve body blew out and bilges flooded to depth of two feet before gaining control with drain pump. Ventilation supply blower shifted out of alignment. Stern planes and rudder developed high noise level. Bow plane tilting and rigging motors grounded. Numerous external electrical cables pushed through pressure hull packing glands, some by as much as one foot. QC sound head grounded internally and JK head was rendered insensitive. Miscellaneous other minor damage occurred. Patrol was terminated.

SEAL (SS183)

11/16/42
(5th)

Off Palau Islands
06°-18'N.
135°-20'E.

Ramming

While at 61 foot depth and only twelve seconds after firing torpedoes at a Japanese freighter, SEAL was run down by a second Japanese cargo ship which passed directly overhead and damaged the periscopes, radar, and their supporting shears. Boat rose from 61 feet to 55 feet due to suction effect and hung there for nearly a minute before starting down. No. 2 periscope, which was fully extended, was bent nearly horizontal at top of shears. 3D radar mast was also bent over in same direction. No. 1 periscope could not be operated due to misalignment of upper bearings. No. 2 periscope housing was broken off level with top of housing for No. 1 periscope. No other damage occurred. Patrol was terminated.

--256--


NAME

DATE

PLACE

SOURCE

REMARKS

SNAPPER (SS185)

11/24/42
(5th)

Off Northern Solomons
07°-58'S.
156°-12'E.

Bombs- 3
Depth Charges - 18

Received one large and two small bombs from unidentified Japanese aircraft while at periscope depth. Six minutes later, while running at 200 foot depth, 18 depth charges were dropped by Japanese destroyers. Bow buoyancy and MBT Nos. 2B and 2D vent valve gaskets were blown out. Low pressure blow line to FBT Nos. 5 and 6 ruptured. Light bulbs were broken throughout ship. Miscellaneous other minor damage occurred. Ship remained on patrol.

STINGRAY (SS186)

12/10/42
(5th)

Off Northern Solomons
06°-25'S.
156°-01'E.

Bombs - 2

Japanese float plane dropped two bombs just as No. 2 periscope (high) broke water for observation. Sea was glassy smooth. Concussion or possibly fragment of bomb shattered glass over periscope object prism, allowing periscope to flood and rendering it inoperative. No other damage occurred. Patrol was terminated due to this damage.

AMBERJACK (SS219)

12/20/42
(2nd)

Off Northern Solomons
7°-10'S.
155°-21'E.

Depth Charges - 6

Depth charged by Japanese destroyer while at 250 foot depth. Head window of No. 1 periscope was shattered and upper prism of No. 2 periscope was chipped. SJ radar mast was thrown out of alignment. MBT No. 1 vent line was sprung and leaked steadily at periscope depth. Other minor damage occurred. Ship remained on patrol.

--257--


NAME

DATE

PLACE

SOURCE

REMARKS

PIKE (SS173)

1/14/43
(6th)

Off Ichie Saki, Southern Honshu

Depth Charges - 69
Bombs - 2

Severely depth charged by several Japanese destroyers over 8 hour period. First 3 charges detonated beneath ship while passing 65 foot depth on way down. Over 40 charges were then received during next hour while running at about 330 foot depth. Main propulsion power was momentarily lost when first depth charge tripped main motor overload relays. Flame and smoke issued from control stand. Brush rigging shifted 5 inches on No. 2 main motor. Dowel pins came loose and brushes chattered on all main motors. Pump room auxiliary power circuit breaker tripped open. Impulse air system leaked heavily both internally and externally. Starboard stern tube developed serious leakage, filling motor room bilges and flooding starboard circulating water pump and standby lube oil pump motors. Leakage through main engine exhaust valves and at flanged and silver brazed joints in main engine circulating water lines flooded engine room bilges and grounded No. 1 main generator blower motor. Main vent values fluttered with each close charge and developed numerous leaks. Trim pump motor controller starting coil dropped out of position and pump could only be operated by holding coil In place by hand. Over half of all light bulbs broke throughout ship. Many electrical grounds occurred in auxiliary machinery motor and controller circuits, i.e. systems, bridge instruments, etc. Numerous valves opened. Gauges and meters were broken or deranged. Muzzle doors were sprung on several torpedo tubes, allowing tubes to flood, and stop bolts and gyro spindles were bent. Plastic composition in variable tanks was shaken loose and large pieces were found in both the forward and aft torpedo tubes. Six hours after initial attack, PIKE went to periscope depth but was promptly bombed by Japanese plane and again went deep. Large air bubbles were noted at this time rising to surface from impulse system forward and aft. Throughout the entire period the boat was heavy overall and depth control was maintained by running at standard and full speed with hard rise on bow and stern planes. Maximum depth reached was 365 feet. Upon finally evading the enemy PIKE surfaced and cleared area on all four main engines. Patrol was terminated.

--258--


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REMARKS

SILVERSIDES 1/18/45 (SS236) (4th)

Off Central Carolines
6°-21'N.
150°-23'E.

Depth Charges
(No. not reported)

Depth charged while at deep submergence by Japanese minelayer or small destroyer. First barrage dislodged gasket from safety tank vent valve and shortly afterwards, when it became necessary to put a bubble in safety tank to maintain depth control, the air escaped through the vent to the surface, disclosing ship's location to enemy. The escorts promptly delivered another attack, this time quite close. Crew's head flushing line ruptured in FBT No. 5 and studs broke on blank flange in FBT No. 3, allowing considerable fuel oil to leak to sea. Japanese ZEKE followed oil trail for 45 minutes and finally attacked with depth bomb but missed SILVERSIDES by 4000 yards. Air vent opened on hydraulic line to engine induction outboard valve, causing valve to later slam shut when running surfaced on four engines. Sea valve leaked over No. 1 main generator terminals, later caused explosion and fire. Pipe plug blew out and nipple broke on two circulating water lines. Valves backed off, instruments were deranged, lights broke, etc. Damage incurred from this depth charging was a factor in early termination of patrol.

SPEARFISH 1/19/43 (SS190) (7th)

Off Gilbert Islands
04°-44'N.
175°-28'E.

Bombs - 2

Bombed by unidentified aircraft while passing 140 foot depth. Several main motor brushes and spring assemblies were dislodged from their holders. No. 2 periscope upper limit switch derangement caused 230 volt ground. Steam-tight lamps in conning tower shattered. Water closet porcelain bowl was broken. Main engine outboard exhaust valves, which had previously been leaking excessively, were effectively seated. Gaskets for safety tank and MBT No. 4 main vent valves were blown out. Miscellaneous other minor damage occurred. Ship was enroute Pearl Harbor from patrol.

--259--


NAME

DATE

PLACE

SOURCE

REMARKS

GUDGEON (SS211)

1/26/43 (6th)

Banda Sea
3°-59'S.
127°-54'E.

Depth Charges - 8

Depth charged by Japanese SC while running at 315 foot depth. Pressure hull was slightly dished inward between frames 118 and 119 in after torpedo room. External high pressure air leaks occurred at bank No. 2 and internal leaks occurred at bank No. 4. Starboard shaft and propeller became noisy and strut bearing developed squeal. Port stern tube leaked excessively and vibrated. QC sound gear shaft was forced out of alignment and chattered. Emergency fresh water tanks split seams and lost water. Gyro spindles were bent on several torpedo tubes. Leak occurred at brazed joint on main engine lube oil line. Hydraulic leak started in piping to stern planes. Gyro follow-up system grounded at damaged panel. No. 2 periscope optics were slightly deranged. Radio antennae insulators broke. Leak occurred between NFO No. 2 and MBT Nos. 2A and 2B. Ship remained on patrol.

GROWLER (SS215)

2/7/43 (4th)

Off New Britain
3°-34'S.
151°-09'E.

Collision & Machine Gun Fire (13mm)

Collided with large Japanese gunboat and received subsequent close quarter enemy machine gun fire. Severe damage resulted to bow structure. See Section XIII for detailed account. Ship terminated patrol.

SWORDFISH (SS193)

2/7/43 (7th)

150 Mi. North of New Ireland
00°-12'N.
152°-00'E.

Aircraft Strafing (.50 cal.)

Strafed by .50 cal. AP projectiles from U.S. Army B-17 bomber which approached SWORDFISH from 20° on the bow at an altitude of about 500 feet. SWORDFISH made a quick dive but received about 20 hits in bridge, conning tower fairwater and superstructure. Damage was as follows: (a) forward engine room access hatch skirt was struck by one projectile which did not penetrate completely but cracked the plating, causing minor leakage into boat; (b) pressure proof battery exhaust ventilation piping was punctured forward of conning tower, causing external system to flood completely; (c) one puncture occurred in low pressure blow line to MBT No. 3; (d) one puncture occurred in MBT No. 2A vent riser; (e) several projectiles ricocheted from top of conning tower pressure plating, causing nicks about 1/16 inch deep. Patrol was terminated.

--260--


NAME

DATE

PLACE

SOURCE

REMARKS

BLACKFISH (SS221)

2/19/43
(3rd)

Bay of Biscay
43°-30'N.
02°-54'W.

Depth Charges - 9

Depth charged by two German converted trawlers while going deep. Conning tower after bulkhead door frame was cracked, causing serious leakage into conning tower. Upper flanges of MBT Nos. 1 and 7 vent risers leaked into torpedo rooms. Engine air induction piping developed considerable leakage as drains showed full stream. Ship went to bottom in 368 feet of water until enemy departed. Patrol was terminated due to conning tower door damage.

RUNNER (SS275)

2/19/43
(1st)

Off Palau Islands
7°-35'N.
134°-25'E.

Bomb - 1

Received one bomb from unidentified Japanese aircraft while firing torpedoes at periscope depth. Bomb detonated to port, close aboard conning tower. Main and emergency lighting was lost in the conning tower and adjacent compartments. Shock damage to control panel contacts put bow plane tilting motor out of commission for several hours but planes were shifted to hand control. Both periscope head windows were shattered, No. 1 periscope upper prism fractured, and the tubes of both periscopes flooded. Power to trim pump, drain pump, hydraulic pump and other auxiliaries was temporarily lost. Mercury was displaced from master gyrocompass, putting it out of commission and the magnetic compass binnacle tube flooded, preventing its use for steering. Serious leakage occurred in conning tower around binnacle tube flange and after bulkhead door. Bridge instruments were smashed and flooded. Numerous external electrical cables were flooded. Low pressure blow valve to MBT No. 1 opened, allowing low pressure manifold to flood. SJ radar bearing indicator shaft was bent. Numerous gauges, meters and instruments were broken or deranged and much other minor damage occurred. Immediately after the bombing, and in spite of the damage, RUNNER fired two more torpedoes and then went to 200 foot depth to evade enemy surface vessels. The patrol was terminated due to derangement of both periscopes.

--261--


NAME

DATE

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SOURCE

REMARKS

KINGFISH (SS234)

3/23/43
(3rd)

Off Formosa
26°-20'N.
121°-55*E.

Depth Charges - 41

Depth charged by small Japanese destroyer or minelayer while

at 300 foot depth. Severe damage resulted. See Section V

for detailed account. Ship terminated patrol.

HADDOCK (SS231)

4/3/43
(4th)

Off Palau Islands
09°-31'N.
133°-39'E.

Depth Charges - 24

Depth charged by Japanese corvette. Two charges detonated close aboard while passing 250 foot depth and several more close charges were received while at 350 foot depth. As attacks continued, HADDOCK increased depth still further. When 415 foot depth was reached, two local areas of conning tower pressure plating, port and starboard, suddenly bulged inward to a maximum extent of about four inches in way of discontinuity in connection of external stiffeners to conning tower plating. Conning tower was promptly abandoned and boat planed up to 300 foot depth. With exception of misalignment of SJ radar training mechanism, no other damage occurred. Ship terminated patrol.

GATO (SS212)

4/1/43
(5th)

Off New Ireland
3°-08'S.
153°-00'E.

Depth Charges - 6

Depth charged by Japanese corvette. First charge detonated close aboard port side aft while passing 150 foot depth and caused major portion of damage sustained. Main battery positive and negative bus bars in control cubicle jarred together and arced, causing battery disconnect switches to trip. Main power was consequently disrupted for brief period but was regained in time to check descent at 380 foot depth. Auxiliary power was also lost by tripping of auxiliary power panel switches but was restored immediately. Pressure hull plating was dished inward between frs. 119-130, both port and starboard, in way of after torpedo room and after trim tank. Maximum indentation was 2 inches. Grease line nipple in after trim tank failed, allowing that tank to completely flood from sea. After WRT tank then flooded from after trim through leaking valves. All four after torpedo tubes were distorted sufficiently to require their renewal. Torpedoes within the after tubes were damaged as well as guide studs and tube operating gear. Steering ram cylinders were thrown out of alignment. MBT No. 1 riser leaked slightly at flanges. Miscellaneous other damage of minor nature occurred, principally in after portion of ship. Ship terminated patrol due to inability to maintain satisfactory depth control because of leakage into after trim tank.

--262--


NAME

DATE

PLACE

SOURCE

REMARKS

PIKE (SS173)

4/23/43
(7th)

Off Central Carolines
4°-20'N.
152°-02'E.

Depth Charges - 8

Depth charged by Japanese escort while at 250 foot depth. Insulators for generator and battery bus bars in control cubicle shattered in numerous places. Leak occurred at cone joint connecting high pressure air line to 200 lb. air manifold. Silver soldered joint ruptured on No. 4 main engine circulating water line. Overload relay for main motor cooling system pump tripped, putting pump temporarily out of commission and standby circulating water pump for main motor cooling system flooded from motor room bilges when ship took large up angle. Blower for No. 2 main motor and stern plane motor jarred out of alignment. Numerous gauges, instruments, and light bulbs were broken or deranged and other minor damage occurred. Patrol was terminated due to control cubicle casualty.

POLLACK (SS180)

5/20/43
(7th)

Off Southern Marshalls
6°-47'N.
169°-42'E.

Depth Charges - 21

Depth charged by Japanese CHIDORI Class torpedo boat while at deep submergence (exact depth not reported). Main battery contactors in control cubicle tripped open, causing temporary loss of all propulsion power. Bow planes lost power and stalled on hard dive position. Auxiliary power contacts for several pumps in engine room closed, starting pumps. Hydraulic line to MBT No. 7 flood valve carried away, allowing considerable oil to escape from hydraulic system. Low pressure blow line to MBT No. 7 was ruptured. After bodies flooded on three torpedoes loaded in tubes. Firing circuit for No. 2 torpedo tube was shorted by loose stud which fell across terminal connections in conning tower. Miscellaneous other minor damage occurred. Ship remained on patrol.

--263--


NAME

DATE

PLACE

SOURCE

REMARKS

TINOSA (SS283)

6/10/43
(1st)

Off Kyushu

31°-14'N.
132°-44'E.

Depth Charges - 12

Depth charged by Japanese PC while heading deep Immediately after firing torpedoes. One charge detonated close aboard while passing 200 foot depth. Bridge instruments were smashed and flooded. Mercury was displaced from both gyrocompasses. Trim pump motor controller cover jarred loose, grounding starter, and trim pump snifter line sheared off, placing pump temporarily out of commission. Radio antenna trunk flooded. Numerous gauges and instruments were deranged, light bulbs broke, and miscellaneous other minor damage occurred. Ship remained on patrol.

SARGO (SS188)

6/14/43
(7th)

Off Palau Islands
06°-40'N.
136°-59'E.

Depth Charges - 4

Depth charged by Japanese SC while submerged (depth not reported). No. 1 deck torpedo tube was put out of commission for remainder of patrol due to rupture of forward roller drain. No. 1 low pressure blower reduction gear crankcase fractured, placing blower out of commission. External flanges on forward torpedo tube impulse air system developed leaks to sea and Nos. 2, 3, and 5 high pressure air bank piping also developed leaks. MBT No. 1 vent valve gasket was dislodged. Key in bow plane tilting linkage in forward torpedo room was jarred out but was immediately replaced. Several gauges were deranged and numerous valves backed off. Ship remained on patrol.

GUARDFISH (SS217)

6/19/43
(5th)

North of Bismarck Archipelago
2°-00'N.
148°-14'E.

Depth Charges - 7

Depth charged by Japanese SC while at 325 feet. First charges forced boat down to 360 feet. Both JK-QC and QB sound gear were disabled due to power fuses becoming dislodged. MBT No. 1 vent riser leaked at two flanges. External high pressure air leaks occurred at banks Nos. 4 and 5, requiring after halves to be secured. TBT's on bridge flooded, Stop bolts and gyro spindles were bent on several torpedo tubes. Pitometer log was deranged. Miscellaneous other minor damage occurred. Ship remained on patrol.

--264--


NAME

DATE

PLACE

SOURCE

REMARKS

JACK (SS259)

6/26/43
(1st)

Off Southern Honshu
33°-22'N.
138°-56'E.

Bomb - 1

Bombed by unidentified Japanese aircraft while at periscope depth preparing to fire torpedoes. Bomb detonated close aboard port quarter. Stern broached. Bow and stern plane power control was lost. Stern planes were quickly shifted to hand operation but control was not regained until several minutes later on bow planes due to obstructing chain guard in forward torpedo room. Boat took 25° down angle and went deep. Descent was checked at 380 feet by blowing bow buoyancy tank and backing with full power. SJ radar was put out of commission probably due to dipole trouble in mast. No. 2 periscope was deranged. External air leak developed at high pressure air bank in MBT No. 2D. Many torpedo tube gyro spindles, stop bolts and torpedo guide studs were damaged. Main engine air induction piping developed leakage through bolted inspection plates. Gaskets were blown out of safety tank and MBT No. 2A master vent valves. Miscellaneous other minor derangements occurred throughout boat. Ship remained on patrol.

GURNARD (SS254)

7/6/43
(2nd)

Off Palau Islands
7°-33'N.
134°-26'E.

Bombs - 2
Depth Charges - 4

Received two bombs from unidentified Japanese aircraft while passing 90 foot depth shortly after taking periscope observation. Power on bow planes was lost temporarily due to tripping of contacts in rigging interlock switch. Ship took large up angle and started to lose depth. Rise was checked at 55 feet by backing with full power, sending 50 men to forward torpedo room, and flooding negative and variable tanks. Ship then dropped rapidly and passed 450 feet before depth control was regained. Meanwhile 4 depth charges were dropped by Japanese destroyer but these were not close. Stern plane operation became very noisy. Conning tower door frame was cracked (2 in. long) at recess in door frame for lower dog. Engine air induction piping and negative tank developed steady leakage. Ship remained on patrol.

--265--


NAME

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REMARKS

SEAL (SS183)

7/8/43
(7th)

Off Northern Honshu
39°-53'N.
142°-10'E.

Bomb & Depth Charges - 72

Depth charged by ASASHIO Class Japanese destroyer and later bombed by Japanese float plane which followed oil trail caused by first attack. 72 bombs and depth charges were dropped on SEAL over 10 hour period. Except for external fuel oil leakage, the source of which could not be determined, all other damage was of minor nature. Small internal leak developed in fuel oil transfer line in pump room and No. 2 auxiliary tank leaked from sea, causing the boat to become heavy overall. Patrol was terminated due to serious oil leakage.

TUNA (SS203)

7/29/43
(8th)

Off Woodlark Is.
8°-02'S.
152°-07'E.

Bombs - 4

Detected while running surfaced at night by RAAF CATALINA. Submerged immediately and received four bombs close aboard while passing from 70 to 110 feet. Second bomb detonation caused loss of both main and auxiliary power. Bow and stern planes were shifted to hand power. Propulsion power was restored between 200 and 250 foot depth and by backing emergency and blowing tanks descent was checked at 365 foot depth. Hydraulic power was lost and tank vents were not opened in time to prevent broaching so TUNA surfaced. Ship took 18° list. Conning tower door leaked badly. Both batteries showed full voltage ground. Both periscopes were disabled. No. 2 low pressure blower was deranged. All main vent valve gaskets leaked. Miscellaneous other damage of minor nature occurred. Patrol was terminated.

SAURY (SS189)

7/31/43
(7th)

Philippine Sea
27°-03'N.
135°-27'E.

Ramming

Run down by Japanese destroyer while at periscope depth. Destroyer passed directly overhead from abaft the port beam. No depth charges were dropped. Nos. 1 and 2 periscopes, 3D and SJ radar masts and supporting shear structures were bent about 30° to starboard. Holding down bolts on shears parted at "A" frame level and foundations of shears were bent. No. 1 periscope window fractured and tube flooded. Slight leakage into conning tower occurred around hull flange of No. 2 periscope stuffing box at depths below 200 feet. Patrol was terminated.

TUNNY

(SS282)

8/26/43 (4th)

Off Palau Is.
7°-30'N. 134°-20'E.

Depth Charges - 8

Depth charged by Japanese PC while at 300 foot depth. Severe damage resulted. See Section VI for detailed account. Ship terminated patrol.

--266--


NAME

DATE

PLACE

SOURCE

REMARKS

SEAHORSE (SS304)

9/6/43
(1st)

Off Palau Islands
7°-31'N.
134°-21'E.

Depth Charges - 35

Depth charged by Japanese PC and/or gunboat shortly after attacking convoy. Ship's supply ventilation and engine air

induction piping developed leakage at rate of about 2000 lbs. per hour. No. 4 torpedo tube flooded through muzzle door. Vent riser flanges for MBT Nos. 1 and 7 leaked into both torpedo rooms. Packing around bow plane tilting shaft loosened, causing serious leakage. Bridge gyro repeater flooded and water traveled through cable to gyro repeater panel inside ship, salting one switch and grounding several connections. Ship remained on patrol.

SCAMP (SS277)

9/18/43
(4th)

North of New Guinea
0°-41'N.
146°-28'E.

Depth Charges - 15

Depth charged by Japanese destroyer escort while at 320 foot depth. Forward torpedo room took in 7000 lbs. water through ruptured pitometer log gland before gate valve could be secured. Small electrical fire started in trim pump motor controller, which was dislodged from its foundation, and small fire also started in pump room control panel. Bow plane rigging motor shifted on its foundation, preventing power rigging of planes. Engine air induction piping commenced to leak slowly and after engine room induction hull flapper valve was distorted so that it would not properly seat. JK-QC sound gear jammed. Bridge TBT flooded. Many grounds developed in electrical circuits. Stern plane noise level greatly increased. Numerous gauges and meters were deranged or broken and much other minor damage occurred. Ship remained on patrol.

SKATE (SS305)

10/6/43
(1st)

Off Wake Island

Strafing (.25 cal.)

Strafed by Japanese ZEKE while surfaced. Plane came in low from the starboard beam. STS ballistic plating (30 lb.) shielding conning tower was penetrated by one .25 cal. projectile which struck nearly normal to the surface. A second .25 cal. projectile, which also struck almost normal to the plating surface, was stopped just short of passing completely through. Fragment of another projectile severed bourdon tubing of bathythermograph, putting it out of commission. No other damage occurred. Ship remained on patrol.

--267--


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PUFFER (SS268)

10/9/43
(1st)

Makassar Strait
01°-08'N.
119°-31'E.

Depth Charges - 46

Depth charged by CHIDORI Class torpedo boat while at deep submergence. Second escort later joined attack. Depth charging extended over 14 hour period and PUFFER was then tracked for an additional 12 hours by the enemy vessel. Engine air induction and ship's supply ventilation outboard valve gaskets were blown out, allowing both systems to completely flood. All deck hatches, conning tower door and forward escape trunk door fluttered on each close depth charge and leaked continuously thereafter. Boat became heavy overall, principally due to flooding mentioned above. Depth control was maintained by running at slow speed with a 12° up angle and by gradually blowing negative, safety, auxiliary and after trim tanks. Boat reached 500 foot maximum depth. All bilges flooded. Trim pump (reciprocating type) was too noisy to permit its use. Rudder and stern planes developed high noise level, apparently due to misalignment. Leakage developed at external piping silver soldered joints of No. 4 air bank. Radio antenna trunk flooded. Plug for previously removed sea pressure gauge line in maneuvering room water closet sea valve backed out, allowing considerable water to enter after torpedo room. Flanged joint of trim line ruptured in after torpedo room. Both JK-QC and QB sound training motors were grounded by flooding and both sound head shafts were slightly misaligned. No. 1 air conditioning circulating water pump motor grounded due to flooding. Brushes were jarred loose on Nos. 1 and 2 lighting motor generators. Gyro spindles were bent on torpedo tubes Nos. 5, 6, 9 and 10. Air pressure inside boat increased to six pounds above atmospheric, air temperature reached 125° F. and CO2 content increased considerably, causing much discomfort to all hands. Numerous light bulbs, gauges and instruments were broken or deranged and much other minor damage occurred. Dive lasted 38 hours. Ship terminated patrol.

--268--


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ALBACORE (SS218)

11/10/43
(7th)

Off New Ireland
3°-08'S.
150°-17'E.

Bomb
(No. not reported)

Bombed by four-engine U.S. bomber while submerging. Main lighting and auxiliary power were temporarily lost. Stern planes were stalled on 15° dive position. Engine Induction outboard valve went under surface before being closed and induction piping system partially flooded. Ship reached 450 feet before descent could be checked and for next 2-1/2 hours oscillated between 30 feet (broach) and 400 feet, at various angles, the worst of which was a 25 degree up angle at 400 feet. 220 volt ground on forward battery and 90 volt ground on after battery occurred due to acid jarring from battery cells and shorts in emergency lighting circuits. Miscellaneous other minor damage occurred. Ship remained on patrol.

TRIGGER (SS237)

11/13/43
(7th)

East China Sea
32°-57'N.
125°-06'E.

Depth Charges - 5

Depth charged by Japanese MOMI Class destroyer while at 200 foot depth. No. 2 main motor developed noise and vibration due to a commutator segment becoming dislodged and causing brushes to chatter. Steady thump developed in port reduction gear at depths greater than 150 feet at all speeds. No other damage was reported. Ship remained on patrol.

THRESHER (SS200)

11/13/43
(10th)

Off Truk
8°-57'N.
152°-36'E.

Depth Charges - 20

Depth charged by two or three Japanese escorts while at about 300 foot depth. Sea water entered main hydraulic system through leak in external replenishing tank or piping located forward of conning tower. Engine air induction piping and radio antenna trunk flooded. Patrol was terminated due to hydraulic system casualty.

--269--


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NAUTILUS (SS168)

11/19/43
(7th)

Off Tarawa
1°-05'N.
173°-03'E.

Gunfire - 2 (5-inch)

NAUTILUS made a quick dive upon being shelled by U.S. destroyer but received one hit and one near-miss before going under. The hit, a 5-inch common projectile (dud), struck superstructure plating abreast after end of conning tower; demolished low pressure blow lines for after and middle groups of main ballast tanks, preventing blowing of those tanks except by closing emergency vents and using high pressure air; tore jagged hole (1' x 2') in auxiliary engine air induction piping, allowing that system to flood and requiring 6° up angle on the boat with full speed to maintain depth control due to the added weight; ricocheted off conning tower plating leaving a deep gouge one foot long; struck a main strength frame, tearing it from the pressure hull; ricocheted off periscope trunk, bending it and loosening a few rivets; and finally came to rest on tank top in superstructure where it was later retrieved. Pressure hull proper was not penetrated. Voice tube valve at hull in conning tower was damaged so that it could not be closed and considerable Inboard flooding resulted, grounding one high pressure air compressor motor, both periscope motors, one low pressure air compressor motor, two lube oil purifier motors, the IMC, IC frequency control, gyro follow-up system and the IC distribution board. The near-miss, also 5-inch, detonated close aboard aft and ruptured a salt water line to the port main motor cooler, causing motor room bilges to flood. Ship remained on patrol until mission of supporting landing was accomplished.

DRUM (SS228)

11/22/43
(8th)

North of New Guinea
2°-53'N.
141°-36!E.

Depth Charges - 11

Depth charged by two Japanese PC's while at about 300 foot depth. Conning tower after bulkhead plating and door frame cracked in way of door upper hinge. Leakage through crack was minor, however, being only 2 or 3 3 gpm at deep submergence. MBT No. 7 vent riser leaked at flange. Maneuvering room hard patch leaked over control cubicle. Torpedo impulse air system forward leaked slightly. No. 2 periscope optics were deranged. Ship terminated patrol.

--270--


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REMARKS

TINOSA

(SS283)

11/22/43
(4th)

Off Palau Islands
07°-09'N.
134°-34'E.

Depth Charges - 40

Depth charged by Japanese AM and/or PC while at about 300 foot depth. First close detonations caused loss of power on bow and stern planes. Boat took 15 up angle and rose to 250 foot depth, then took 20° down angle and descended to 380 foot depth where ship control was finally regained by shifting to hand operation on planes. I.C. motor generator was disabled, putting rudder angle indicator, diving plane Indicator and gyro compass out of commission. Valve closed on steering hydraulic piping system, rendering it temporarily impossible to move rudder to left. Other minor damage occurred. Ship remained on patrol.

BOWFIN (SS287)

11/28/43
(2nd)

Off Central Philippines
12°-45'N.
109°-42'E.

Gunfire - 1
(3 or 4.7 in.)

While conducting surface torpedo attack on Japanese convoy, an enemy AP or AK opened fire on BOWFIN with a 3-inch or 4.7-inch gun and secured one hit which detonated in superstructure at frame 70 near starboard engine air Induction piping. Fragments punctured induction and hull ventilation piping, low pressure blow lines to middle and after groups of ballast tanks and fuel oil compensating line to stand pipe. Tank top of MBT No. 4a was dished in. Miscellaneous other minor damage occurred to superstructure. Pressure hull proper was not penetrated. Ship's force patched holes sufficiently to permit submerged operations. Patrol was terminated.

SAILFISH (SS192)

12/7/43
(10th)

Off Kyushu
31°-21'N.
154°-10'E.

Bombs - 2

Dived upon hearing strafing approach of Japanese ZEKE aircraft and received two bombs while passing about 40 foot depth. First bomb caused no damage. Second bomb detonated close aboard on starboard side abreast maneuvering room. Main propulsion power was lost temporarily due to the jarring open of main motor field excitation circuits In control cubicle and tripping of starboard main motor reverser contactor which arced and welded itself In open position. No. 1 main motor flashed to ground, its brush rigging insulators cracked and a bare spot was burned on a pole face winding. Repairs to this motor were made but It again flashed over on 9 December and was cut out of service for remainder of patrol. Reduction gear noise level increased markedly as result of bombing. Serious leak developed at hull flange of main motor cooler circulating water discharge line. Other minor damage occurred. Ship remained on patrol.

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POGY (SS266)

12/13/43
(4th)

Off Palau
7°-06'N.
134°-31'E.

Depth Charges - 3

Depth charged by Japanese PC while heading for deep submergence from periscope depth. Pattern of three close charges detonated close aboard while passing 150 feet. All torpedo tube gyro spindles and depth setting spindles were bent. Leakage into MB? No. 4a (source not reported) caused that tank to remain flooded on surfacing and MBT 4B had to be kept flooded during remainder of patrol to compensate for list. Six engine thermometers and after battery air flow meter were broken. No other damage was reported. Ship terminated patrol due to torpedo tube damage, spindle spares being available for only two tubes.

SWORDFISH

(SS195)

1/13/44
(10th)

Off Central Honshu
33°-16-N.
139°-30'E.

Depth Charges - 24

Depth charged by three Japanese escorts while at 320 foot depth. No. 1 periscope lost nitrogen pressure and lenses of No. 2 periscope were jarred out of alignment. JP and JK-QC sound heads were disabled. Cast Iron plug was blown out of main motor cooling piping. Conning tower hatch opened momentarily, allowing water to flood conning tower bilges. Clamping shoe on port main motor parallel contactor in control cubicle jarred loose and a securing wing nut on emergency power cable in pump room backed off but these derangements were not discovered until the next dive. At that time the cable in the pumproom fell against Its cabinet due to the down angle on the boat, starting a fire, and the control cubicle clamping shoe grounded, causing its contactor to weld itself closed. Both main and auxiliary power were lost. Attempts to put the main motors on battery power caused circuit breakers to operate each time due to short circuit in cubicle. Ship finally submerged with power on the starboard shaft only after pulling port main motor disconnect switches. Temporary repairs were made and the ship remained on patrol.

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GATO (SS212)

12/20/43
(7th)

North of Bismarck Archipelago
1°-30'N.
148°-36'E.

Depth Charges - 19

Depth charged by two Japanese SC's while at 370 foot depth. One depth charge did not detonate and landed on deck where it was recovered upon surfacing. Bulkhead at frame 77 was slightly distorted so that W.T. door would not completely seat. Outer hull plating aft was slightly dished between frames. Engine air induction and ship's supply ventilation piping flooded. Riser to MBT No. 1 leaked at hull flange. Many gauges, instruments and light bulbs were broken or deranged and much other minor damage occurred. Ship remained on patrol.

TAMBOR (SS198)

2/3/44
(9th)

East China Sea,
29°11'N.
124°-45'E.

Depth Charges - 32

Depth charged by Japanese destroyer shortly after submerging. First six charges forced ship to bottom in 268 feet of water where she received 26 more charges. Bed plates of both high pressure air compressors fractured around complete periphery. Both low pressure air compressors were dislodged from their foundations. Conning tower after bulkhead door frame cracked. Forward and after fuel oil filling line hull valves jarred partially open and plugs on topside standpipes backed off, allowing oil to leak to sea and thereby disclosing ship's presence to enemy destroyer. Oil also leaked from NFO No. 5 and FBT No. 5 (source not reported). Operating mechanism for ship's supply ventilation hull valve was damaged and valve could not be closed again after it was opened on surfacing. Low power field of No. 1 periscope was deranged. All gyro spindles were bent and torpedo guide studs and tube stop bolts were damaged. High pressure air leaks developed at No. 1 air bank in forward battery well. Stern plane drive shaft pinion bearing was damaged, causing high noise level. Radio antenna trunk partially flooded. QC sound gear training motor housing broke and motor was torn loose from bulkhead. Temporary repairs were made and ship remained on patrol.

--273-

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REMARKS

PERMIT (SS178)

2/13/44
(11th)

Off Western Carolines
7°-42'N.
148°-18'E.

Depth Charges - 33

Depth charged by Japanese destroyers while at 290 foot depth. Engine air induction system flooded and considerable water was taken into engine room bilges through inboard drains and inboard hull valves. All four main engines and both auxiliary engines flooded through leaking inboard and outboard exhaust valves. Ship became heavy aft and overall. Depth control was maintained by increasing speed to 90 rpm with occasional spurts to 180 rpm and by putting 15° to 18° up angle on boat. Maximum depth reached was 320 feet. Ship surfaced three hours later with battery almost depleted. Ship remained on petrol.

TANG

(SS306)

2/23/44
(1st)

Off Marianas Islands
14°-45'N.
144°-32'E.

Detonation
of Ammunition Ship

A Japanese ammunition ship apparently mass detonated following torpedo attack by TANG. Shock of detonation at range of 1400 yards dislodged muzzle door gasket (not T-shaped) from No. 5 torpedo tube while door was open. During later dive, at 400 foot depth the breech door gasket of same tube bulged out under pressure and admitted water to forward torpedo room faster than pumps could handle. Ship remained on patrol.

ROCK (SS274)

2/29/44
(1st)

Off Nansei Shoto Islands
25°-33'N.
130°-42'E.

Gunfire - 1
(5.5 inch)

While conducting night surface radar attack on a Japanese convoy, ROCK was detected by enemy destroyer and shelled at close range. Five seconds after diving, and with both periscopes down, one 5.5 inch projectile struck port side of No. 2 periscope shear about seven feet below top. Numerous fragment holes were torn in periscope and radar shears, conning tower fairwater and bridge decks. Bearings of both periscopes were misaligned so that neither could be raised or trained. The upper prisms of both periscopes were shattered. The SD radar mast flooded. Searchlight and running light cables were severed and water passed through sheathing to terminal boxes in the conning tower. Conning tower and pressure hull were not penetrated at any place by fragments. Miscellaneous other minor damage occurred. Ship terminated patrol.

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TUNNY (SS282)

3/30/44
(5th)

Off Palau Islands
7°-40'N.
134°-00'E.

Bomb - 1

Bombed by U.S. TBF while surfaced on lifeguard duty. War Patrol Report states bomb was 2000 lb. and struck sea 10 yards to starboard of forward engine room, detonating abreast maneuvering room. YORKTOWN (CV10) Air Combat Action Report states bomb was 2000 lb. and struck water about 50 yards off starboard quarter. Boat made quick dive to 150 feet. Shock caused movement of bus bars in control cubicle (shock mounted) and generator bus bar and bus tie closed contactor were burned by arcing to control cell frame. Main propulsion power was taken from battery until electrical repairs were completed next day. Main motor commutators were slightly burned by brushes lifting clear and drawing arc. Numerous hydraulic system leaks occurred from control room to after torpedo room. SJ radar training gear was misaligned and SJ lobe switching motor was disabled. All after torpedo tube muzzle door gaskets were cut and all four remaining torpedoes were damaged. Both torpedo tube blow and vent manifolds were torn loose from their supports. Excessive leakage developed around starboard stern tube gland. Miscellaneous other minor damage occurred. Patrol was terminated due to damage to torpedoes.

RAY (SS271)

3/18/44
(3rd)

Off North Borneo
07°-25'N.
115°-20'E.

Depth Charges - 44

Depth charged by two Japanese escorts while at 365 foot depth. Stern planes temporarily jammed twice in hand power and were noisy In operation. Bridge pelorus glass was shattered. Four-inch deck gun telescope flooded. Auxiliary engine outboard exhaust valve jammed closed and could not be opened In either hydraulic or hand power. Steering system hydraulic by-pass valve nipple broke. Numerous gauges, instruments, and light bulbs were broken or deranged and other minor damage occurred. Ship remained on patrol.

SCAMP (SS277)

4/7/44
(7th)

Off Mindanao, P. I.
5°-02'N.
126°-07'E.

Bomb - 1

Received one bomb from Japanese float plane while passing 40 foot depth. Severe damage resulted. See Section IX for detailed account. Ship terminated patrol.

--275--


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TRIGGER (SS237)

4/8/44
(9th)

Off Marianas Islands
19°-06'N.
142°-31'E.

Depth Charges - 33

Depth charged by several Japanese escorts while at about 300 foot depth. One pattern of six close charges caused majority of damage sustained. Ship's supply ventilation piping topside flooded. Forward torpedo room flooded to level of floor plates through jammed torpedo tube poppet valve. Both sound gear training motors were grounded by flooding. QB sound head was rendered insensitive. Engine room, motor room and pump room bilges flooded to level of lower flats. SD antenna mast head was fractured and mast partially flooded. Both SD and SJ radar transmitters were disabled due to broken tubes. High pressure air leak occurred at No. 2 air bank in MBT No. 2. Electrical fire started in bow plane tilting motor connection box and magnetic brake coils. No. 2 I.C. motor generator was deranged. Steering and stern plane motors jarred out of alignment, running hot and with high noise level. Trim pump lube oil cooler ruptured, allowing sea water to enter pump oil casing. Bridge TBT's flooded. Radio antenna trunk flooded. No. 7 stern torpedo tube shutter jumped track, apparently due to depth charging. Miscellaneous other minor damage occurred. TRIGGER was boxed in by enemy escorts for 17 more hours although running silent at 300 feet. Air temperature inside boat during this period reached 130°. Ship remained on patrol.

PAMPANITO (SS383)

4/7/44
(1st)

Off Marianas Islands
12°-46'N.
143°-49'E.

Depth Charges

- 7

Depth charged by Japanese escort while at deep submergence (depth not reported) Engine air Induction piping topside flooded slowly through leaks at flanged joints. Several rivets on Nos. 1 and 3 main motor brush rigging sheared. Mercury was splashed from auxiliary gyrocompass. Nos. 1 and 2 periscope objective lenses were chipped. Battery cells of torpedo in tube No. 8 cracked; exploder on torpedo in tube No. 2 flooded; afterbodies of torpedoes in tubes Nos. 5 and 6 flooded; muzzle door gaskets on tubes 5, 9 and 10 were cut. Both bridge pressure-proof speakers were damaged and cables to pressure hull from speakers flooded. Many light bulbs were broken. Numerous valves opened, including safety tank inboard vent and outboard vent to No. 1 sanitary tank, allowing the latter tank to flood. Other minor damage occurred. Ship remained on patrol.

--276--


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REMARKS

ROBALO (SS273)

4/24/44
(2nd)

Off French Indo-China
10°-29'N.
109°-26'E.

Bomb - 1

Submerged upon sighting Japanese BETTY and received one bomb close aboard port side forward while passing 55 foot depth. Engine air induction system was inadvertently flooded on dive by personnel error which prevented induction trunk valve from closing in power. This valve was closed by hand before the bomb detonated but depth control was lost temporarily due to boat becoming heavy overall. Descent was checked at 350 feet by putting air bubble in bow buoyancy and safety tanks. SJ radar was disabled both electrically and mechanically. No. 1 periscope upper window shattered and periscope flooded. No. 2 periscope low power field was rendered inoperative. Upper conning tower hatch leaked above 45 foot depth and lower conning tower hatch was distorted so that it would not seat properly. MBT Nos. 1 and 4B main vent valve gaskets were partially blown out and MBT No. 1 riser leaked badly at flange in forward torpedo room. JP sound head was disabled. Radio antenna trunk flooded. Steering system change valve in control room was damaged and caused considerable loss of hydraulic oil. Bridge instruments were smashed and flooded. High pressure air leak occurred at bank in MBT No. 2. Torpedo impulse air system forward also developed external leakage. About 50 light bulbs were broken, including all emergency lights forward of after battery room. Pitometer log sword arm was ruptured and log flooded. Numerous gauges, meters, and instruments were deranged or broken and much other minor damage occurred. Ship remained on patrol.

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REMARKS

CREVALLE (53291)

5/14/44
(3rd)

Off Northern Celebes
0°-57'N.
125°-51'E.

Depth Charges - 16

Depth charged by CHIDORI Class Japanese torpedo boat. First pattern of eight charges detonated close aboard while at 190 foot depth and second pattern of eight detonated shortly afterward while at 400 foot depth. Pressure hull plating was slightly dished inward at frame 21, starboard. Starboard vent riser from MBT No. 1 leaked at flange. Both dogs on forward escape trunk lower hatch sheared off. Locking rings on torpedo tube breech doors rotated towards open position. Flange in officer's head flushing line leaked seriously, causing torpedo room bilges to flood. Sound training motors were thrown out of alignment and flooded. Short circuit in emergency lighting system caused full voltage ground on forward battery. Hydraulic piping leaks forward caused loss of pressure in system. Both periscopes were damaged and SD and SJ radars were disabled. Leakage occurred around steering wheel shaft in conning tower. All sanitary tanks flooded when discharge valves opened. Numerous valves opened, small leaks developed in various piping systems, gauges were deranged, and other minor damage occurred throughout boat. Ship was returning to base when attacked.

PICUDA (SS382)

5/20/44
(2nd)

Luzon Strait
19°-00'N
120°-45'E.

Depth Charges - 14

Depth charged by Japanese escort. Received three close charges while at 70 foot depth. Second charge detonated close abreast conning tower and heeled ship to port. Third charge detonated under stern, forcing stern up and giving ship large down angle. This third detonation also tripped starboard main motor contactor but it was immediately closed and power restored. PICUDA went deep, receiving 4 more close charges at 150 foot depth, 4 at 250 foot depth and 3 at 450 foot depth. Several broken brushes were later found in the Nos. 3 and 4 main motors. Engine air induction line flooded. Contacts in No. 2 I.C. motor generator control panel jarred loose. Trim line sea. suction piping seam split at trim manifold. Brazed joint on No. 2 sanitary flushing line cracked. Lube oil line in after engine room carried away. After torpedo tube gyro spindles were bent and tube No. 9 flooded. Magazine flooding line manifold casting was cracked. Numerous valves jarred open on hydraulic system, fuel oil filling and transfer system and lube oil filling line hull connections. Several pressure gauges and thermometers broke. Heavy rumble developed on port shaft at 50 rpm and higher. Ship remained on patrol.

--278--


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BLUEGILL (SS242)

5/22/44
(1st)

Off Halmahera
4°-00'N.
128°-06'E.

Bombs - 2

Received two bombs close aboard from Japanese BETTY, the first at 40 foot depth just after submerging and the second while passing 200 foot depth. Bow planes lost power while in hard dive position. Depth control was lost and boat took 25° to 30 down angle. Regained depth control at 250 feet by backing emergency and blowing bow buoyancy tank. Bow plane operation was restored by shifting to hand control. SJ radar was disabled and SJ radar mast was thrown out of alignment. No. 1 main motor became noisy due to chattering of displaced brush rigging. Forward battery soft patch leaked. Miscellaneous other minor damage occurred. Ship remained on patrol.

FLYING FISH (SS229)

5/24/44
(10th)

Philippine Sea
12°-54'N.
134°-52'E.

Own Torpedo

While retiring after delivering an attack, a probable premature detonation of one of FLYING FISH's own torpedoes (Mk.18) occurred close aboard aft. Ship was surfaced and proceeding at standard speed on all four main engines. Nos. 1, 2 and 3 main generator contactors in control cubicle tripped under shock and Nos. 1, 2 and 3 main Diesels surged as result of loss of load. Voltmeter fuses for Nos. 1, 2, 3 and 4 main motors and main generators burned out. Severe arcing occurred. No. 4 main generator remained in operation. No. 3 main generator was put on line by estimating voltage and paralleling it with No. 4 generator. Propulsion was then shifted to main batteries. Shock also tripped bow plane rigging motor panel contactors, causing pilot circuit fuses to blow. Planes were rigged out by hand on subsequent dive. Ship remained on patrol.

PERMIT (SS178)

5/28/44
(12th)

Off Truk
06°-45'N.
151°-52'E.

Bomb - 1

Detected by U.S. VENTURA bomber while running surfaced. Submerged immediately and received one bomb close aboard while passing 15 foot depth. Drain line to compensating system in forward torpedo room carried away, spraying sound gear, pitometer log and other equipment with oil and salt water. Power was lost on bow planes. After battery developed full voltage ground. High pressure air manifold developed leaks. Various bridge instruments flooded out. Numerous gauges and instruments were broken or deranged. Ship remained on patrol.

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RATON (SS270)

6/6/44
(4th)

Off French Indo-China
8°-58'N.
109°-30'E.

Depth Charges - 57

Depth charged by several Japanese escorts. First five charges detonated close aboard while running at periscope depth. Vent riser on MBT No. 1 developed leak at flange. QB sound training gear jarred out of alignment and became noisy. JP receiver crystal earphones were deranged and power fuse blew. Pump drive on pitometer log jarred out of alignment. IMC bridge microphone coupling boxes and cables flooded. Four-inch deck gun flooded. Numerous light bulbs were broken and gauges were put out of calibration. Gyro pots and after bodies flooded on three remaining torpedoes loaded in tubes. No other damage occurred. Ship remained on patrol.

WHALE

(SS239)

6/8/44
(8th)

North of Bonin Islands
31°-00'N.
143°-55'E.

Depth Charges - 29

Depth charged by three or four Japanese escorts while at about 350 foot depth. Both propulsion shafts developed vibrations at 70-80 rpm after depth charging and noise level increased, indicating shaft misalignment. Four holding down bolts sheared on reduction gear casings. No. 3 main motor developed squeal at 50 to 70 rpm. No. 2 periscope stuffing gland leaked heavily. Compensating line ruptured in superstructure, causing loss in pressure on fuel oil tank system when surfaced. Vision of both periscopes was impaired by dirt being jarred loose and settling on lenses. SJ and SD radars were disabled. High pressure air line at No. 4 air bank developed small leak. Miscellaneous other minor damage occurred. Ship remained on patrol.

APOGON (SS308)

7/12/44
(4th)

Luzon Strait
19°-51'N.
123°-04'E.

Ramming

While conducting night periscope attack on Japanese convoy, APOGON was rammed from starboard by an enemy AK which passed directly overhead. Depth at time of collision was about 70 feet to keel. Boat was heeled 15° to port. Top of shears, both periscopes and SD and SJ radar masts were bent about 45° to port. No. 1 periscope was sheared off about 8 feet from its head. Water entered conning tower at rate of about 30 gpm, most of it through leaking SJ mast stuffing box. Several depth charges were dropped as APOGON went deep but did no damage. Boat was then caught at 430 foot depth by putting air bubble In safety tank and using trim and drain pump on bilges. Patrol was terminated.

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SAND LANCE (SS381)

8/7/44
(3rd)

Off Northern Celebes
1°-18'N.
121°-30'E.

Bombs - 2
Depth Charges (No. not reported)

Received two bombs from Japanese DAVE float plane while passing 70 feet on way up to periscope depth. Bombs detonated close under stern, causing ship to broach. SAND LANCE then went to 430 foot depth to evade surface ship depth charging which followed. Port reduction gear was damaged and developed such a loud knocking noise that port shaft was secured. Starboard propulsion plant control cubicle controllers were jammed by a broken washer, limiting maximum speed on that shaft to two-thirds. At 430 feet it was discovered that Mk. 18 torpedo in No. 8 tube was running hot so ship was planed up to 100 foot depth to fire torpedo. Warhead detonated prematurely about twenty seconds after torpedo left tube. Other damage was minor. Ship terminated patrol as result of reduction gear damage. Return trip was made using starboard shaft only.

TUNNY (SS282)

9/1/44
(7th)

Luzon Strait
21°-50'N.
119°-18'E.

Bombs - 2

Dived to escape Japanese KATE aircraft. While passing 110 feet, two depth bombs detonated close aboard aft on port side. Second bomb forced boat from 4° down angle to 8° up angle. Both bombs probably were 60 Kg size, set for detonation at 25 meters depth. Pressure hull plating was dished In between several frames on port side in way of after torpedo room and after end of maneuvering room. Maximum indentation of plating was about 1 inch. Entire propulsion plant was undamaged. Serious leakage occurred at two flanges of port vent riser for MBT No. 7 in after torpedo room, distorted by inward movement of pressure hull aft. This leakage was determining factor in decision to terminate patrol. Gyro setting spindles were bent on all torpedo tubes except No. 1. Pull voltage ground developed due to short circuits in emergency lighting system. Numerous valves jarred open. Rudder was canted to starboard about 3° at bottom. Small leak occurred at union on high pressure air line to separator in after torpedo room. Miscellaneous other minor damage occurred. Ship terminated patrol and returned to base with no difficulty.

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ICEFISH (SS367)

10/26/44
(1st)

Luzon Strait
19°-04'N.
120°-36'E.

Depth Charges - 16

Depth charged by Japanese escorts while at 420 foot depth. Severe hull flexural vibrations occurred. 225-pound air supply valve to hydraulic oil vent and replenishing tank jarred open and valve wheel was knocked off. Resulting air pressure forced air volume tank safety valve open, blew down vent and replenishing tank and opened 45 lb. relief valves with consequent loss of most of oil in hydraulic system. Hydraulic system throughout boat developed many piping leaks and line to bow buoyancy vent valve completely carried away. Steering and bow and stern planes went out of commission until oil could be put back in telemotors and then could only be operated In hand control since main hydraulic plant was air bound. Even in hand operation, air in piping to bow and stern planes and steering caused loud knocking noises which disclosed ship's location to enemy escorts. Valves jarred open throughout ship, causing full sea pressure on salt water systems. Numerous air, fuel oil and salt water leaks developed. No. 1 sanitary tank flooded and blew through water closet and inboard vent into forward torpedo room. Fuel oil leaked to depth of 2 inches on deck in after battery room through opened fuel tank inboard vent. Serious periscope packing gland leaks caused water to flood into conning tower bilges and thence into control room and periscope wells. Vent riser piping topside for FBT Nos. 3B and 4B was dished In to depth of 4 inches over 4 to 5 foot length. Low power field In No. 1 periscope was deranged. All bow torpedo tube gyro spindles were bent and could not be withdrawn. Torpedo in No. 4 tube had "hot" run, hydrogen explosion or both. Guide studs on all torpedoes were sheared back about 1 inch. All bow tube inner door locking rings rotated open 1/3 of circumference. Numerous small electrical fires and grounds occurred. Most light bulbs throughout ship were broken. Coil In tube nest of No. 2 generator cooler ruptured. JP and QB sound gear were disabled. Numerous other items of minor damage occurred. Main propulsion and vital auxiliaries were undamaged except for hydraulically operated equipment. Ship terminated patrol.

SALMON (SS182)

10/30/44
(11th)

Off Kyushu
30°-08'N.
132°-33'E.

Depth Charges - 30

Depth charged by two or more Japanese escorts while at 310 foot depth. Severe damage resulted. See Section VII for detailed account. Ship terminated patrol.

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GUITARRO
(SS363)

10/31/44
(3rd)

Off Central Luzon
15°-17'N.
119°-49'E.

Detonation of Ammunition Ship

A few seconds after heading for deep submergence from periscope depth, two of GUITARRO's torpedoes scored hits on a, Japanese ammunition ship of about 7500 gross tonnage. The resulting mass detonation, 1900 yards distant, forced GUITARRO down rapidly 50 feet in depth. Blue flame is reported to have appeared around both periscope stuffing boxes and after engine room hatch. Inboard vents on NFO No. 1 and FBT No. 3 jarred open under shock and showered forward torpedo room and crew's mess with fuel oil. Pitometer log sword connection was blown off, spraying sound training motor generator and JP-1 sound gear with sea water. Brushes were dislodged from steering motor. Several valve wheels were knocked off and numerous light bulbs were broken. Knock developed in port reduction gear. Ship remained on patrol.

SAILFISH (SS192)

11/4/44
(12th)

Luzon Strait
20°-09'N.
121°-43'E.

Bombs - 10

Received about ten bombs from unidentified Japanese aircraft while at periscope depth during attack on destroyer "killer" group. No bombs landed very close but one detonation caused No. 7 torpedo tube inboard vent valve to jam open. SAILFISH then headed for deep submergence. Large volume of water entered after torpedo room through this vent before it could be secured and flooded forward end of compartment to depth of 6 inches above deck due to 5° dive angle on boat. Torpedo charging panel grounded from water spray and small electrical fire started. Fire was immediately extinguished by de-energizing the panel but boat then took 25° up angle due to added weight aft and started for surface. Depth control was regained at 170 feet by backing with both shafts and sending men forward. Ship remained on patrol.

GUITARRO (SS363)

11/6/44
(3rd)

Off Central Luzon
15°-54'N.
119°-44'E.

Depth Charges - 6

Depth charged by Japanese escort while at deep submergence (depth not reported). Boat was forced down an additional 50 feet. SD and SJ radars were disabled. Stern planes and steering gear were thrown out of alignment and became noisy. All bridge electrical circuits shorted and 1 1/4 inch pressure proof quartz in bridge gyro repeater was shattered. Radio transmitter was disabled and antennae insulators topside fractured. Both periscope stadimeters jarred out of adjustment. Many emergency light bulbs were broken. Ship remained on patrol.

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HALIBUT (SS232)

11/14/44
(10th)

Luzon Strait
20°-56'N.
121°-33'E.

Bombs - 4
Depth Charges - 8 or 10

Detected by Japanese plane or planes, apparently equipped with MAD, while attacking convoy at periscope depth. Pour heavy explosions, believed to be depth bombs, occurred within next four minutes but little damage resulted. Twenty minutes later, while at 325 foot depth, severe structural damage was received forward and a great amount of other damage occurred elsewhere throughout ship as a result of close pattern of 8 or 10 depth charges dropped by surface escort. Ship was forced down to 420 feet. Pressure hull plating forward of frame 54 was depressed inward between frames, port and starboard, to maximum depth of about 2 inches (damage in way of forward torpedo room was similar to TUNNY, PLATE VI). Top and sides of MBT No. 1 buckled In forward torpedo room. Bulkhead between forward torpedo room and forward battery compartment buckled. Pressure hull dished inward to depth of 2 inches between forward escape trunk and torpedo loading hatch. Pressure hull plating and framing distortion also occurred in local areas as far aft as forward engine room, including conning tower, safety and auxiliary tanks, and after lube oil tanks (fr. 103 - 108). No. 1 h.p. air bank "tee" carried away, allowing bank to bleed down and caused pressure in forward battery compartment to build up to about 50 psi. This pressure was gradually distributed throughout ship, venting into forward torpedo room by cracking bulkhead door and into control room through trim line hose connection. Pinal overall increase in internal air pressure was 10 psi. Forward escape trunk flooded. Eleven forward battery jars cracked, loosing electrolyte. Bases cracked on ice machine and air conditioning compressors. Both gyrocompasses were deranged. Both main propulsion shafts became noisy. JP sound gear was disabled. Minor damage was sustained by JK-QC and QB sound heads. SD radar mast flooded. VHF and APR were disabled. Batteries in four Mk.18-1 torpedoes forward were damaged beyond repair. Sea valves jarred open throughout ship. No damage occurred to main engines, generators, reduction gears, control cubicle, bow and stern planes, trim pump, hydraulic plant, or any other vital systems or auxiliary machinery with exception of high pressure air system casualty described above. Ship surfaced after attack and returned to base with no difficulty.

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BLUEGILL (SS242)

11/17/44
(3rd)

Makassar Strait
00°-48'N.
118°-52'E.

Depth Charges - 47

Depth charged by two or more CHIDORI Class Japanese torpedo boats. First charges were received while running at 312 foot depth. Later close charges forced boat down to 384 feet. Forward torpedo loading hatch lifted momentarily. No. 1 MBT vent riser leaked heavily at flange to master vent valve. JP sound gear was disabled. Gyro spindles were bent on all forward torpedo tubes. Many hydraulic system leaks occurred forward. No. 3 sanitary tank flooded through overboard discharge. Auxiliary engine outboard exhaust valve jammed in closed position due to bent stem. Stern plane motor was repeatedly energized due to panel contacts closing with each near detonation. Many light bulbs were broken in main and emergency lighting system, numerous valves jarred open throughout boat, gauges and instruments were broken or deranged, minor piping leaks developed, many electrical grounds occurred and miscellaneous other minor damage was sustained. Ship remained on patrol.

RONQUIL (SS396)

11/17/44
(2nd)

Off Central Honshu
32°-15'N.
140°-00'E.

Gunfire - 1 (40mm)

While firing directly astern during gun action with Japanese armed trawler, one of RONQUIL's own 40mm shells apparently detonated either prematurely or on contact with lifeline stanchion aft. Detonation occurred over after torpedo room loading hatch and damage was confined between frames 107 and 115. Pressure hull was penetrated by fragments in two places: (a) 1 1/2" hole between frames 107 and 108 forward of torpedo loading hatch, (b) 1/2" hole in torpedo loading hatch. Pressure hull plating and loading hatch were gouged by fragments in numerous areas. Lube oil filling line, low pressure blow line to MBT No. 7 and high salvage air line to after torpedo room were punctured by fragments. Superstructure deck was riddled between frames 107 and 115. Miscellaneous other minor damage occurred. Pressure hull holes were patched sufficiently well to permit shallow dives and held tight during close bombing which followed one hour after patches were installed. Ship terminated patrol.

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PARGO (SS264)

11/26/44
(6th)

Off Sarawak
4°-55'N.
114°-06'E.

Depth Charges - 34

Depth charged by two Japanese AM's while running at 160 foot depth in 180 feet of water. Auxiliary engine outboard exhaust valve operating gear jammed and could not be opened by power or hand. Circuit breakers tripped on both I. C. motor generators. No. 2 electric still developed small leak in coils, causing salted distillate. SJ radar lobing mechanism was disabled. Numerous gauges, instruments and light bulbs were broken or deranged and other minor damage occurred. Ship remained on patrol.

PIPEFISH (SS388)

11/30/44
(3rd)

Off Hainan, South China Sea
18°-07'N.
111°-35'E.

Bombs - 3

Submerged upon sighting Japanese VAL aircraft and received 3 bombs close aboard shortly thereafter. Power was lost on stern planes due to electrical damage to tilting motor control panel. Controllers for Nos. 1 and 2 hydraulic pump motors tripped. Torpedo in No. 5 tube ran "hot". Three torpedo tube gyro spindles and one depth setting spindle were bent. Guide studs on all loaded torpedoes were partially sheared. Forward escape trunk 225-pound blow valve opened. 225-pound air volume tank in after torpedo room tore loose from its supporting brackets. Leaks developed in main motor circulating water line and at hydraulic steering control valve. Radio antenna insulators fractured. Numerous light bulbs broke. Miscellaneous other minor damage occurred. Ship remained on patrol.

BERGALL (SS320)

12/13/44
(2nd)

Off French Indo-China
8°-10'N.
105°-31'E.

Gunfire - 1
(8-inch dud)

After completing night surface radar attack on two Japanese heavy cruisers, sinking the first and probably damaging the second, BERGALL was fired on by the latter cruiser with 3 salvos of 2 rounds each from 9000 yards range, receiving one 8-inch/50 cal. dud hit. This projectile passed through forward torpedo room loading hatch structure from port to starboard, tearing a large hole in pressure hull. Shell did not detonate. Fragments torn from hull caused additional damage. Starboard vent riser from MBT No. 1 was punctured, allowing that tank to vent and flood; ventilation system flapper valve in after bulkhead of forward torpedo room was damaged; 225-pound service air line forward was punctured; overhead cables in torpedo room were cut, causing failure of many electrical circuits and several Small fires. BERGALL returned to base running entire distance on the surface. Improvised patches were Installed over loading hatch damage and MBT No. 1 riser by ship's force.

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REDFISH (SS395)

12/19/44
(2nd)

East China Sea
28°-59'N.
124°-03'E.

Depth Charges - 13

Depth charged by Japanese destroyer shortly after attacking and sinking large CV (UNRYU). Received seven very close charges while passing 150 foot depth. Ship then bottomed in 232 feet of water for next 1 1/2 hours, receiving only six more close charges in spite of intense enemy A/S activity. Severe damage was sustained. Pressure hull plating was slightly dished inward between frames in several areas in way of forward torpedo room and forward trim tank. Tank top plating of MBT No. 1 in forward torpedo room was rippled between frames. MBT No. 1 starboard vent riser leaked profusely at flanged joint. No. 1 sanitary tank overboard discharge sea valve leaked heavily at hull flange and through valve itself. Considerable hydraulic oil was lost due to leaks at flanges on lines to pump room accumulator, steering manifold aft and sonar and bow plane tilting piping forward. This loss of oil disabled entire hydraulic system temporarily, stalling rudder in hard left position and bow planes on 20 rise angle. Failure of hydraulic power also prevented raising of JK-QC sound gear so that it was damaged when ship hit bottom. Torpedo in tube No. 8 ran "hot". Controller for trim pump and starter for low pressure blower were damaged. Metal fuse retained in emergency lighting fuse box jarred loose, causing zero ground. JP sonar shaft was bent and JP head flooded. Both gyrocompasses were deranged. At least 12 battery jars forward were cracked, losing electrolyte and causing full voltage ground. 3100 gallons fuel oil shifted from NFO Nos. 1 and 2 to FBT No. 3 due to fuel oil filling and transfer valves jarring open. Numerous gauges, instruments, and light bulbs were deranged or broken, electrical grounds developed in many systems and equipment, and much other minor damage occurred. Ship terminated patrol and returned to base using all main engines and occasionally diving without difficulty.

BARBERO (SS317)

12/27/44
(2nd)

Lombok Strait
8°-20'S.
115°-55'E.

Bomb - 1

Received one bomb close aboard aft from unidentified aircraft while at periscope depth. Port reduction gear developed loud knock and grinding sound and was placed out of commission to prevent further damage. Several brushes jarred out of position on No. 2 main motor. No other damage was sustained. Ship returned to base using starboard shaft only. Port reduction gear was subsequently replaced.

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GREENLING (SS213)

1/25/45
(12th)

Off Nansei Shoto Islands
29°-27'N.
130°-09'E.

Depth Charges - 95

Four Japanese destroyers or large PC's dropped 95 depth charges on GREENLING over a 2-1/2 hour period. Several close charges were received while running at 300 foot depth, forcing ship down to 360 foot depth. Pressure hull plating was dished slightly between frames In several areas aft of frame 105. Frames 127 and 138 were buckled in after trim tank. Main engine mufflers Nos. 1 and 2 were damaged. No. 2 high pressure air compressor bed plate in pump room cracked. High pressure air leaks developed at control room manifold and in forward engine room at No. 5 bank "tee". Five torpedoes ran "hot'* in tubes as result of damage to stop bolts and guide studs. Both gyro compasses displaced mercury. Miscellaneous other minor damage occurred, principally in after portion of ship. Patrol was terminated.

THREADFIN (SS410)

1/30/45
(1st)

Off Southern Honshu
33°-20'N.
135°-30'E.

Depth Charges
(No. not reported)

Depth charged by several Japanese PC's. First close charges were received while running at 300 foot depth and caused serious leak in cross-connection piping between compensating line and motor cooling system in motor room. Salt water spray barely missed energized control cubicle bus bars. Bucket brigade kept water level in bilges below main motors. Boat went to bottom in 450 feet of water for remainder of attack and the ruptured line was blanked. No other damage was sustained. Ship remained on patrol.

BURRFISH (SS312)

2/11/45
(5th)

Off Bonin Islands
27°-51'N.
141°-55'E.

Depth Charges - 39
Bombs - 20

Depth charged by Japanese PC and depth bombed by several Japanese planes while operating at various depths up to 450 feet. No. 5 torpedo impulse air piping developed leak outside hull. All torpedoes loaded in tubes sustained guide stud damage. Negative tank developed leak through flood valve. Miscellaneous other minor damage occurred. Ship remained on patrol.

--288--


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REMARKS

PINTADO (SS387)

2/20/45
(4th)

Gulf of Siam
7°-25'N.
104°-41'E.

Bombs - 2

Submerged upon sighting Japanese DINAH aircraft and received two bombs close aboard while passing 130 foot depth. Loud squeal developed at low speeds (below 50 rpm) on port shaft, apparently due to misalignment of port strut bearing. 5 torpedo gyro spindles were bent. Port revolution counter synchro motor was disengaged from its gear train. Stern plane angle indicator system was put out of commission. Several fuses and light bulbs were blown out and a few valves jarred open. No other damage was reported. Ship remained on patrol.

PETO
(SS265)

3/5/45
(8th)

Off Hainan, South China Sea
20°-57'N.
111°-56'E.

Bombs - 3

Submerged upon night approach of unidentified radar-equipped aircraft and received three bombs while passing 80 foot depth. Hydraulic system was put out of commission temporarily due to derangement of hydraulic accumulator charging mechanism which prevented movement of pilot valve to open automatic by-pass valve. Oil pressure Increased, causing relief valve to open. Deck gun deflection shaft was bent. No other damage was reported. Ship remained on patrol.

BREAM (SS243)

3/15/45
(5th)

Off North Borneo
5°-36'S.
114°-33'E.

Depth Charges - 18

Depth charged by CHIDORI Class Japanese torpedo boat. First two charges forced ship to bottom in 100 feet of water where 16 more charges were delivered close aboard. Auxiliary engine flooded through leaking Inboard and outboard exhaust valves. Numerous sea valves opened by as much as two full turns. Forward escape trunk flooded through W.T. door and upper hatch. After battery compartment hatch trunk flooded through upper hatch when its dogs loosened. Both gyrocompasses were disabled. Conning tower hatch lifted slightly and admitted small quantity of water. Bow planes could not be rigged In due to electrical interlock derangement. Air leaks developed in forward torpedo impulse air piping outside hull and from No. 1 high pressure air bank in forward battery compartment. Numerous other items of minor damage occurred throughout boat. Patrol was terminated although BREAM was in sufficiently good materiel condition to make an attack while proceeding to base.

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DEVILFISH (SS292)

3/20/45
(2nd)

West of Bonin Islands
28°-55'N.
137°-35'E.

Suicide Plane Crash

While submerging and passing 50 foot depth, a suicide crash was made on DEVILFISH by Japanese ZEKE fighter plane. Parts of plane struck uppermost portion of periscope shears. Nos. 1 and 2 periscopes were damaged both mechanically and optically. Periscope shears proper were forced slightly out of alignment. SJ radar mast was ruptured at top and water entered conning tower in large volume through damaged antenna assembly at lower end of mast. Conning tower bilges filled and water poured down lower hatch to control room. SD, ST, APR and VHF antennae were destroyed. SD, SJ, SPA and sonar equipment in conning tower were grounded out by flooding and spray. Ship terminated patrol.

BAYA (SS318)

3/21/45
(3rd)

Off French Indo-China
11°-55'N.
109°-18'E.

Depth Charges - 21

Depth charged by Japanese SC while at 220 foot depth. First charges forced ship to bottom in 270 feet of water. Main lighting power was lost. Conning tower hatch fluttered. Numerous sea valves backed off from 1 to 5 turns. 5 torpedo gyro spindles were bent. Pronounced knock developed in port reduction gear. Both periscopes and the master and auxiliary gyrocompasses were deranged. Ship remained on patrol.

POGY (SS266)

4/19/45
(9th)

Southeast of Honshu
32°-17'N.
140°-14'E.

Strafing and Bomb - 1

Submerged upon strafing attack by approaching U.S. B-24 bomber and received one bomb while passing 30 foot depth. Following damage was caused by .30 cal. and .50 cal. projectiles: (a) VHF and APR antennae coaxial feeder pipes were punctured and water entered these pipes, passed through open hull shear valves and sprayed on radio equipment in radio room before shear valves could be closed; (b) radio antenna trunk was punctured and flooded; (c) safety latch operating rod on 5"/25 cal. deck gun was broken in two by projectile; (d) two .50 cal. projectiles penetrated STS plating below cigarette deck and entered 40 lb. STS ready service stowage for 5"/25 cal. ammunition - no damage occurred to six rounds of high capacity ammunition within; (e) after TBT on bridge was grounded by projectile damage to cable; (f) port radio antenna was shot away; (g) numerous projectiles punctured bridge and periscope shears. No damage was caused by bomb detonation. Ship remained on patrol.

--290--


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BLACKFIN (SS322)

3/28/45
(3rd)

Off Hon Traunam South China Sea

Depth Charges - 7

Depth charged by Japanese destroyer escort while at about 100 foot depth. Seven charges detonated above and to starboard, forcing ship to bottom in 156 feet of water. Bow planes jammed on 8 degrees dive position. Hydraulic power for stern planes was lost when high vent on telemotor line jarred open. Three Mk. 18-1 torpedoes forward and one Mk. 23 torpedo aft, loaded in tubes, had "hot" runs. Gyro spindles and stop bolts on tubes both forward and aft were damaged. Hydrogen burner rubber sockets were dislodged from torpedo tubes Nos. 2 and 5 and, since outer doors were open, water poured into forward torpedo room until wooden depth charge plugs were Inserted. Both sound heads were damaged when boat hit bottom. 225-pound air to forward escape trunk jarred open, causing pressure to build up and forcing trunk W.T. door partially open. After battery compartment access trunk upper hatch opened momentarily and trunk lower hatch was knocked off its seat, allowing small quantity of water to enter ship. Six-inch cracks extending from after lower corner of No. 8 unit crank case doors to idler and drive gear housings by after holding down studs were later discovered on all four main engines (General Motors, 16-278A). These cracks were not caused by depth charging but were due to construction welding stresses combined with normal service stresses. All radio antennae were knocked down. All compasses were disabled. Numerous valves opened throughout ship and minor air leaks developed. Gauges, meters, and light bulbs were broken or deranged. Patrol was terminated.

CHUB (SS329)

4/12/45
(1st)

Java Sea
6°-03'S.
113°-56'E.

Bombs - 4

Submerged upon sighting Japanese RUFE aircraft and received 4 small bombs while passing 80 foot depth with hard rise on both bow and stern planes (due to proximity of 19 fathom sounding on chart). Detonation caused hydraulic system automatic by-pass valve to lift and remain open long enough to allow oil in replenishing tank to run back to supply tank. This caused loss of power on both bow and stern planes. Ship broached before power was restored. Optics of No. 2 periscope were deranged. Bow buoyancy vent valve was unseated. Battery of torpedo loaded in No. 1 tube jarred loose, causing damage to hydrogen burner assembly. Other minor damage occurred. Ship remained on patrol.

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SEAHORSE (SS304)

4/18/45
(7th)

Tsushima Strait
33°-45'N.
128°-26'E.

Depth Charges - 50

Depth charged by two Japanese frigates. First pattern of 8 or 9 charges was received close aboard and forced boat from 300 foot to 400 foot depth. Propulsion was then secured and SEAHORSE settled on bottom in 470 feet of water. About 40 more charges were dropped but were not close. Damage was extensive. Both reduction gears developed pounding noise at all speeds and starboard shaft groaned loudly, apparently due to strut bearing damage. Sea water entered reduction gear lube oil sumps through rupture In lube oil coolers. Inboard exhaust valve for No. 4 main engine could not be closed. Fresh water expansion tanks for Nos. 2 and 4 engines were cracked. Nos. 1 and 2 air conditioning compressors shifted out of alignment and numerous leaks developed in freon piping. Acid was jarred from many after main battery cells, causing full ground. Conning tower bulkhead cracked slightly around weld for steering wheel packing gland, causing small leak. Hard patches in pressure hull of three compartments developed leaks. Leakage around SD radar mast hydraulic cylinder hull flanges flooded storeroom below. Engine induction outboard valve could not be opened in power due to binding of valve on guide rods. Engine air induction piping flooded and sea water entered boat through distorted engine room induction hull valve. Radio antenna trunk flooded and all radio antennae Insulators fractured. Auxiliary tank flooded through sea valve which jarred open. Inboard vent piping for FBT No. 5 riser carried away, allowing fuel oil to enter boat. Hydraulic system oil poured out through ruptured line to SD radar mast. Bridge instruments, both periscopes and all radio and radar gear were permanently damaged or temporarily disabled. All torpedo gyro spindles and torpedo tube stop bolts were bent. Torpedo data computer jarred out of alignment. Training and elevating mechanism on 40 mm gun was inoperable. Training mechanism on 5-inch deck gun was misaligned and 5-inch ammunition hoist breech door was sprung, allowing hoist to flood. Emergency lighting power failed in after half of ship. Gauges, meters and instruments were broken or deranged, cork insulation was jarred loose in large quantity, and much other minor damage occurred. Ship terminated patrol.

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PERCH (II) (SS313)

4/26/45
(6th)

Off North Borneo
5°-32'S.
116°-07'E.

Depth Charges - 30

Depth charged by Japanese minelayer while running at 160 foot depth in 180 feet of water. Flushing line from crew's head developed leak in FBT No. 4b and small amount of fuel oil entered after battery compartment through leak at hull flange of this line. No. 2 periscope was disabled In low power and fogged in high power. Brushes in steering motor were jarred out of alignment. Numerous minor leaks started in freon lines, internal salvage air piping, hydraulic lines and high pressure air lines. Mercury was displaced from auxiliary gyrocompass. Tube in SD radar transmitter broke. JK-QC and QB sonar shafts were misaligned. JP-1 sonar was disabled due to blown fuses, broken tube and short in electrical system. Numerous gauges, light bulbs, brackets, meters and fuses were broken or deranged, and other minor damage occurred. Ship remained on patrol.

COBIA (SS245)

5/14/45
(5 th)

Gulf of Siam
09°-35'N.
101°-44'E.

Depth Charges - 16

Depth charged by Japanese minelayer while at 120 foot depth. First charges forced boat to bottom in 148 feet of water. Water closet valves spun to full open on each of several close detonations. Gyro spindles were bent on six torpedo tubes. Battery and generator busses in control cubicle arced, causing flame and smoke, and contactors were welded together by heat. Main power was secured. High pressure air line from No. 5 air bank carried away between hull and hull stop valve, allowing bank to bleed down. JK-QC sound projector was damaged on grounding. Access hatch trunks flooded in engine room and after battery compartment. Other minor damage occurred. Ship remained on patrol.

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BERGALL (SS320)

6/13/45 (5th)

Gulf of Siam
11°-45'N.
99°-50'E.

Mine - 1

Swept U.S. or British proximity-fuzed mine while surfaced. See Section XI for detailed account. Ship terminated patrol as result of damage.

PARCHE (SS384)

6/26/45
(6th)

Off Northern Honshu
39°-25'N.
142°-04'E.

Depth Charges - 67

Depth charged by six Japanese CHIDORI and SC escorts. 16 close charges detonated below ship while running at about 300 foot depth. No. 2 sanitary tank flooded completely through outboard vent valve which jarred open. Inboard vent had not been closed and considerable flooding occurred in crews' mess and washroom through this line. Boat went to 550 foot depth with 8° up angle. Noise level from shafts and reduction gears increased. Bendix log, dead reckoning analyzer indicator, and Mk. VII gyro compass follow-up alarm system were deranged. Both sonar training motors flooded with bilge water due to up angle on boat. Inboard flapper valve of 5-inch ammunition scuttle jarred open as much as 3 inches with each close charge. Other minor damage occurred. Ship remained on patrol.

HAWKBILL (SS366)

7/18/45
(5th)

Off Malay States, South China Sea
04°-41'N.
103°-30'E.

Depth Charges
(No. not reported)

While at periscope depth, KAMIKAZE Class destroyer passed directly overhead and dropped close depth charge pattern which detonated under ship. Auxiliary power was lost at once. Ship broached with 20° up angle, exposing 60 feet of the hull forward with bow 20 feet above surface. HAWKBILL immediately re-submerged by backing with full power and flooding negative tank Main motors were then secured and boat was put on the bottom in 110 feet of water. No additional close attacks were received. Knock developed in starboard reduction gear. Low power optics of No. 2 periscope were deranged. Lobe switching failed on SJ radar. SD transmitter and SD antenna mast limit switches were damaged. Controller and starting resistance for JC-QC sound gear training motor were put out of commission. Bathythermograph was damaged beyond repair. Mercury was displaced from both master and auxiliary gyrocompasses and electrical leads to master compass were severed. Both radio receivers and TBL transmitter were deranged. One main storage battery cell cracked, resulting in loss of electrolyte. Many light bulbs broke and various meters and gauges were deranged. Other minor damage occurred. Patrol was terminated.

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CERO (SS225)

7/18/45
(8th)

Off Kurlle Islands
45°-14'N.
143°-41'E.

Bomb - 1

Received one light bomb from Japanese GRACE aircraft while submerging and passing 43 feet. No. 1 periscope was put out of commission. Bridge "covered wagon" structure was distorted slightly and bridge deck buckled. Bridge instruments were disabled. Mercury was displaced from auxiliary gyro compass. Miscellaneous other minor damage occurred. Patrol was terminated.

PARGO (SS264)

7/27/44
(4th)

Off Northern Celebes
1°-35'N.
125°-20'E.

Bombs - 2
Depth Charges - 48

Received one bomb from Japanese PETE aircraft while at periscope depth, and a second bomb while going deep. During next 1 1/2 hours two Japanese CM's dropped about 48 depth charges on PARGO while running at deep submergence. No. 2 sanitary tank flooded. Radio antenna trunk flooded through broken insulator. Electrical interlock on bow plane tilting circuit was deranged so that planes could not be rigged. Overspeed trips on Nos. 1 and 2 turbo-blowers opened. Outboard exhaust valve on No. 4 main engine jammed. Auxiliary gyrocompass displaced mercury. Numerous gauges, instruments and light bulbs were broken or deranged and other minor damage occurred. Ship remained on patrol.

MUSKALLUNGE (SS262)

3/8/45
(7th)

Off Kurile Islands
46°-41'N.
151°-43'E.

Gunfire (.30 cal.)

Received several .30 caliber projectile hits during gun action with a group of seven Japanese sea trucks. Average range during engagement was about 350 yards. Only materiel damage caused, other than numerous penetrations of superstructure plating, was the holing of a periscope hydraulic cylinder by two projectiles. Ship remained on patrol.

--295--


APPENDIX II

Tabular Summary of U.S. Submarine Losses During World War II

1. A tabular summary of all United States submarine losses incurred throughout World War II is presented on the following pages. This summary is based upon information contained in the publication entitled "U. S. Submarine Losses, World War II" prepared by the Commander Submarine Force, Pacific Fleet, and ComSubPacAdmin ltr. FF12-10(A)/A16-2, Serial No. 00349 of 21 September 1945 (Statements of Survivors of U. S. Submarines Lost in Action). In arriving at the conclusions set forth in the referenced publication regarding the circumstances of each submarine loss, all of the following sources were considered:

(a) The operation order delineating each submarine's mission and assigned patrol areas.

(b) Dispatches sent to and received from each submarine during the patrol on which lost.

(c) Reports of Allied aircraft, surface ships ana submarines, particularly those operating in conjunction with the lost submarine as a coordinated attack group, containing mention of contacts, rendezvous, submarine actions against enemy shipping, enemy anti-submarine attacks, or other evidence which might indicate the presence of the submarine concerned or furnish information on its loss.

(d) Reports of enemy or Allied mines in the assigned patrol areas or routes to and from those areas.

(e) Statements of survivors, repatriated prisoners of war and friendly guerilla forces.

(f) A list of anti-submarine attacks provided by the Japanese upon termination of the war.

2. Source (f), the list of Japanese anti-submarine attacks made during World War II, consists of two sections, both supposedly exact translations, and contains only those actions which the Japanese assessed as resulting in positive sinkings. The first section gives the date and location of each attack; the second section contains brief amplifying comments on certain attacks, particularly those made after July 1943 when the Japanese claim to have commenced more rigid investigation of reported sinkings. In many cases no

--296--


information is available as to whether the attacks were made by surface ships, planes or submarines. Unfortunately, those attacks which were thought to be ineffective, or whose dates or locations were uncertain, were not recorded by the Japanese. In addition, there are many anti-submarine attacks that are known to have occurred, including several cases where our submarines were lost and survivors were captured by the Japanese, which are not contained in the list since apparently either no report was ever made to a central Japanese agency or the attacking ships or planes were themselves lost before returning to base. It should be borne in mind that one or more of these unrecorded attacks might better explain the loss of certain submarines which in the summary below have been attributed to other attacks, mines, or for which no known attack could conceivably have applied. However, the Japanese were prone to accept the most inconclusive evidence as proof of a sinking and for that reason their list is probably fairly complete. For example, it contains a total of 468 "positive" sinkings, whereas at most only 41* U.S. submarine losses were due directly to Japanese action, including passive means such as mines. Where only one listed attack could be tied in with a submarine loss, in the absence of better information it has been designated in the tabular summary below as the probable cause of the loss.

3. The geographical locations given in the summary correspond with those attacks or other information on which the explanation of the loss of each submarine is based. However, several submarines departed from their bases and were never heard from again nor is any information available as to their loss. For such cases the estimated position is given as inside the area to which the submarine was assigned but the loss might have occurred anywhere between that area and the base.

4. It is to be expected that further data may become available in the future which will modify some of the conclusions presented below.

5. For the purpose of indicating the accuracy of the conclusions reached for each submarine loss in the summary, integers have been placed after the name of each submarine with meanings as follows:

1 - Certain (based upon survivors' reports or known schedule of training operations).
2 - Probable (based upon strong circumstantial evidence obtained from one or more of the sources enumerated in paragraph (1) above).
3 - Possible (based upon inconclusive circumstantial evidence obtained from one or more of the sources enumerated in paragraph (1) above).
4 - Conjecture (a possible hypothesis advanced in the absence of any applicable circumstantial or direct evidence but based on the known presence of mines in the submarine's assigned patrol area).
5 - Unknown (no information available).


* U.S. Submarine Losses, World War II

--297--


NO.

SS NO

NAME

DATE OF LOSS

LOCATION OF LOSS

CAUSE OF LOSS

REMARKS

1

195

SEALION 1

12/10/41

U.S. Navy Yard, Cavite, P.I.

Bombs - 2

Struck by two small bombs during Japanese aircraft attack on Navy Yard, Cavite. First bomb detonated in conning tower fair-water a few feet above pressure hull, demolishing conning tower after bulkhead and engine air induction and battery ventilation trunks. Pressure hull over control room was pierced by numerous fragments. Second bomb penetrated pressure hull and detonated inside after engine room causing that space to flood rapidly. Forward engine room and after torpedo room flooded slowly through bulkhead fragment holes. Stern sank to bottom. Repair facilities not being available, SEALION was blown up 25 December 1941 to prevent capture by Japanese forces.

2

141

S-36 1

1/20/42
(2nd Patrol)

Makassar Strait

Stranding

Stranded on Taka Bakang Reef off southern Celebes. Forward battery room was holed and flooded, causing generation of chlorine gas. Ship was abandoned and destroyed by U.S. forces on 21 January 1942.

3

131

S-26 1

1/24/42

Gulf of Panama

Collision

Collided with PC-460 while surfaced and enroute to patrol area. Starboard side of torpedo room was holed. Ship sank in 300 feet of water within a few seconds. The three and only survivors were on bridge at time of collision.

4

174

SHARK (I) 3

2/11/42 to 2/21/42
(2nd Patrol)

Off Celebes

Depth Charge

Last heard from on 7 February 1942. Japanese records indicate three attacks, one or more of which may have accounted for loss of SHARK. The first and most likely attack was that by surface ship off Menado, Celebes, on 11 February 1942. The second was north of Kendari, Celebes, on 17 February 1942 and the third was east of Kendari on 21 February 1942.

5

176

PERCH 1

3/3/42
(2nd Patrol)

Java Sea

Depth Charge

Scuttled by own crew after Japanese depth charge attacks. See Section IV for details of loss.

6

132

S-27 1

6/19/42
(1st Patrol)

Off Amchitka, Aleutian Islands

Stranding

Stranded on reef 400 yards off Amchitka Island. Torpedo room flooded. After battery room made water and chlorine gas was generated. Ship assumed 8 to 12 degrees trim by the bow after grounding. Ship was abandoned.

7

216

GRUNION 5

7/30/42 to 8/6/42
(1st Patrol)

Off Aleutian Islands

Unknown

Last heard from on 30 July 1942 off Kiska at which time she reported strong Japanese anti-submarine activity. On the same day, GRUNION was directed to return to Dutch Harbor and should have arrived by 6 August 1942. No explanation of loss Is available from Japanese sources.

8

144

S-39 1

8/14/42
(5th Patrol)

Off Rossel Island, Louisiade Archipelago

Stranding

Stranded on submerged reef. Ballast tanks were ruptured by pounding in heavy seas and ship assumed 60 degrees port list. Ship was abandoned.

9

APS 1

ARGONAUT 2

1/10/43
(3rd Patrol)

Off New Britain, Bismarck Archipelago

Depth Charge and Gunfire

U.S. Army bomber observed ARGONAUT forced to surface by depth charge attack of Japanese destroyers and sunk by gunfire. Action occurred off New Britain on 10 January 1943.

10

219

AMBERJACK 3

2/16/43
(3rd Patrol)

Off New Britain, Bismarck Archipelago

Bomb and Depth Charge

Last heard from on 14 February 1943. Japanese records indicate several attacks any one of which might have accounted for loss of AMBER JACK. The most likely action was a. combined attack by one patrol plane and two surface escorts on 16 February 1943. It was reported that a large amount of oil and "parts of the hull" came to the surface.

--298-- / --299--


NO.

SS NO.

NAME

DATE OF LOSS

LOCATION OF LOSS

CAUSE OF LOSS

REMARKS

11

207

GRAMPUS 5

3/6/43
(6th Patrol)

Blackett Strait, Solomon Islands

Gunfire

Never heard from again after departing Brisbane, Australia on 12 February 1943. Japanese records indicate two attacks, either of which might have accounted for loss of GRAMPUS. However, on the basis of other evidence, It appears more likely that she was caught on the surface by Japanese destroyers passing through Blackett Strait on the night of 5-6 March and was sunk by gunfire. Since the destroyers were themselves subsequently sunk, Japanese reports contain no mention of such an attack.

12

201

TRITON 2

3/15/43
(6th Patrol)

North of New Guinea

Depth Charge

Last heard from on 11 March 1943. Japanese information indicates that TRITON was almost certainly sunk by depth charge attack of Japanese destroyers on 15 March 1943. It was reported that "a great quantity of oil, pieces of wood, cork and manufactured goods bearing the label 'Made in U.S.A.' " was sighted after the attack.

13

177

PICKEREL 3

4/3/43
(7th Patrol)

Off Northern Honshu

Depth Charge

Never heard from again after departing Midway on 22 March 1943. Japanese information indicates PICKEREL was possibly sunk by depth charge attack off Shiramuka. Lighthouse, Honshu on 3 April 1943.

14

210

GRENADIER 1

4/22/43
(6th Patrol)

Off Penang, Malaya

Bomb

Scuttled by own crew after aircraft bomb attack. See Section VIII for details of loss.

15

89

R-12 1

6/12/43

Off Key West, Florida

Operational or Materiel Casualty

Lost during training exercises off Key West, Florida. While surfaced, rapid flooding occurred forward for unknown reasons and the boat sank In about 15 seconds. The five officers and men on the bridge were the only survivors. The opinion of the Court of Inquiry was that the flooding could not be traced to any known cause but probably occurred through a torpedo tube.

16

275

RUNNER 4

5/28/43 to 7/4/43
(3rd Patrol)

Off Northern Honshu

Mine

Never heard from again after departing Midway on 28 May 1943. Japanese records indicate no attacks which could conceivably have accounted for loss of RUNNER. It is considered possible that she may have been destroyed by a mine for there were at least four known minefields in her assigned patrol area.

17

209

GRAYLING 5

9/9/43 to 9/12/43
(8th Patrol)

Off Manila, P.I.

Unknown

Last heard from on 23 August 1943. Japanese records indicate no attacks which could conceivably have accounted for loss of GRAYLING.

18

181

POMPANO 4

8/20/43 to 9/27/43
(7th Patrol)

Off Northern Honshu

Mine

Never heard from again after departing Midway on 20 August 1943. Japanese records indicate no attacks which could conceivably have accounted for loss of POMPANO. It is considered possible that she may have been destroyed by a mine for her assigned patrol areas were known to have been heavily mined.

19

290

CISCO 3

9/28/43
(1st Patrol)

Sulu Sea

Bomb and Depth Charge

Never heard from again after departing Port Darwin, Australia on 19 September 1943. Japanese records indicate that CISCO may have been sunk in the Sulu Sea. by combined aircraft and surface ship attack on 28 September 1943. It was reported that "oil continued to gush out even on tenth of October",

20

155

S-44 1

10/7/43
(5th Patrol)

Off Kamchatka, Okhotsk Sea

Gunfire

While surfaced at night, S-44 opened fire with her deck gun on a target believed to be a small enemy merchant ship but which actually was a Japanese destroyer. The immediate and accurate return fire of the destroyer sank S-44 before she could escape by submerging. About eight men escaped before the boat went under but only two of these were rescued.

--300-- / --301--


NO.

SS NO

NAME

DATE OF LOSS

LOCATION OF LOSS

CAUSE OF LOSS

REMARKS

21

238

WAHOO 3

10/11/43
(7th Patrol)

La, Perouse Strait, Sea of Japan

Bomb

WAHOO was never heard from again after departing Midway on 13 September 1943, although she is known to have sunk a Japanese ship in the Sea of Japan near the Straits of Tsushima on 5 October 1943. Japanese information indicates that she was possibly sunk by aircraft attack on 11 October 1943 while passing through La Perouse Strait on her way out of the Sea of Japan.

22

248

DORADO

10/12/43

Off U.S. East Coast

Unknown

Never beard from again after departing Submarine Base, New London on 6 October 1943 for Panama Canal. There were no definite conclusions as to the cause of loss. Possible causes could have been operational casualties, enemy action, or attack by friendly forces.

23

226

CORVINA 2

11/16/43
(1st Patrol)

South of Truk

Torpedo (Sub.)

Never heard from again after departing Johnston Island on 6 November 1943. Japanese records Indicate that CORVINA was torpedoed while surfaced by a Japanese submarine. Two of the three torpedoes which were fired were reported to have hit.

24

191

SCULPIN 1

11/19/43
(9th Patrol)

North of Truk

Depth Charge

While preparing to attack a Japanese convoy on the night of 18 November 1943, SCULPIN was detected by Japanese destroyers and depth charged. The first series of depth charges caused only minor damage. The ship then broached when the diving officer attempted to plane up to periscope depth, the depth gage having stuck at a reading of 125 feet, and the enemy destroyers renewed the attack at once. About noon on 19 November, another series of depth charges damaged SCULPIN severely. The pressure hull was dished in, torpedo tube bulkheads were cracked, valves leaked, bow and stern planes were damaged and the boat was badly out of trim, about 180 shaft r.p.m. being required to maintain depth control. The boat at this time went to a reported maximum depth of about 500 feet. With batteries rapidly nearing depletion and the crew exhausted, SCULPIN was then forced to make a battle surface. When in the ensuing gun action it became apparent that escape was impossible, the ship was scuttled by diving at emergency speed with all vents open. Forty-two men abandoned ship before SCULPIN sank and of these, twenty-one survived the end of the war.

25

289

CAPELIN 3

11/23/43 to 12/9/43
(2nd Patrol)

Off Halmahera, Moluccas

Depth Charge

Never heard from again after departing Port Darwin, Australia on 17 November 1943. Japanese records list an attack on a U.S. submarine off Kaoe Bay, Halmahera, on 23 November 1943, but the action was Incomplete and evidence of contact was slight. However, this is the only reported attack which could possibly have caused the loss of CAPELIN.

26

SS278

SCORPION 4

1/5/44 to 2/24/44
(4th Patrol)

Yellow Sea

Mine

Last heard from during rendezvous with HERRING (SS233) on 6 January 1944. Japanese records indicate no attacks which could conceivably have accounted for loss of SCORPION. It is considered possible that she may have been destroyed by known minefields at the entrance to the Yellow Sea while proceeding to or departing from her assigned patrol area.

27

208

GRAYBACK 2

2/26/44
(10th Patrol)

Off Okinawa

Bomb and Depth Charge

Last heard from on 25 February 1944. Japanese records indicate that GRAYBACK was probably sunk on 26 February by the combined attack of a. carrier plane and surface escorts. It was reported that the plane sighted a surfaced U.S. submarine and "gave a direct hit at the sub, which exploded and sank immediately".

--302-- / --303--


NO.

SS NO.

NAME

DATE OF LOSS

LOCATION OF LOSS

CAUSE OF LOSS

REMARKS

28

202

TROUT 2

2/29/44
(11th Patrol)

Philippine Sea

Depth Charge

Japanese records list the sinking of SAKITO MARU on 29 February 1944 in position 22°-40'N, 131°-45'E in the Philippine Sea. TROUT is the only U.S. submarine which could have made this attack and since she did not report the sinking, it is probable that she was lost during or shortly after this action.

29

284

TULLIBEE 1

3/26/44
(4th Patrol)

Off Palau Islands

Own Torpedo

According to the one lone survivor, a minute or two after firing two torpedoes at a target ship on the night of 26 March 1944, TULLIBEE was damaged by a heavy explosion and sank immediately. Although there is no conclusive evidence, it is considered quite likely that the explosion was caused by a circular run of one of TULLIBEE's own torpedoes.

30

211

GUDGEON 5

4/7/44 to 5/12/44
(12th Patrol)

Off Marianas Islands

Bomb and Depth Charge

Never heard from again after departing Johnston Island on 7 April 1944. Japanese records indicate at least two attacks which might have accounted for loss of GUDGEON but the information furnished is too limited to permit any conclusions. Heavy anti-submarine activity, both aircraft and surface ship, was noted by SILVER-SIDES (SS236), TUNNY (SS282) and SANDLANCE (SS381) off the Marianas Islands on 12 May 1944 slightly to the south of GUDGEON'S assigned area and it is possible that these attacks were responsible for her loss.

31

233

HERRING 2

6/1/44
(8th Patrol)

Off Matsuwa To, Kurile Islands

Gunfire

Last heard from during rendezvous with BARB (SS220) on 31 May 1944. Japanese information indicates that HERRING was sunk on 1 June 1944 by gunfire from shore batteries shortly after torpedoing two merchant ships anchored at Matsuwa. The report stated that two direct hits were scored on the conning tower and that "bubbles covered an area about 5 meters wide, and heavy oil covered an area, of approximately 15 miles".

32

361

GOLET 2

6/14/44 (2nd Patrol)

Off Northern Honshu

Depth Charge

Never heard from again after departing Midway on 28 May 1944. Japanese information indicates that GOLET was probably sunk off Northern Honshu by surface ship attack on 14 June 1944. It was reported that "corks, raft, etc., and a heavy oil pool" were found at the scene of the action.

33

133

S-28 1

7/4/44

Off Oahu, T. H.

Operational or Materiel Casualty

Lost while on training exercises off Oahu, T.H. Submerged and never resurfaced. Nature of casualty which caused loss is unknown.

34

273

ROBALO 1

7/26/44
(3rd Patrol)

Balabac Strait

Mine

Information contained in a note written by survivors of ROBALO, none of whom lived to the end of the war, and also from a Philippine guerilla leader, indicates that ROBALO was sunk on 26 July 1944 while east of Balabac Island. The note stated that the sinking was caused by explosion of the after battery. It is believed more likely, however, that ROBALO was mined. No Japanese information is available. FLIER (SS250) was also apparently mined in this same area two weeks later.

35

250

FLIER 1

8/13/44
(2nd Patrol)

Balabac Strait

Mine

Explosion occurred forward while proceeding on the surface through Balabac Strait on the night of 13 August 1944. Ship is reported to have sunk in 20 or 30 seconds. About 15 men abandoned ship before she sank and of these only eight were able to swim ashore and survive. Explosion is believed to have been contact mine.

36

257

HARDER 2

8/24/44
(6th Patrol)

Off Luzon South China Sea

Depth Charge

Information received from both the Japanese and HAKE (SS256) indicates that HARDER was sunk by depth charge attack off central Luzon on 24 August 1944. The Japanese report stated that "much oil, wood chips and cork floated in the neighborhood".

--304-- / --305--


NO.

SS NO,

NAME

DATE OF LOSS

LOCATION OF LOSS

CAUSE OF LOSS

REMARKS

37

197

SEAWOLF 5

10/3/44
(15th Patrol)

Off Halmahera, Moluccas

Unknown

Assessment of all available information does not establish cause of loss but indicates the possibility that the ship may have been lost during anti-submarine attacks on a Japanese submarine.

38

294

ESCOLAR 4

10/17/44 to 11/3/44
(1st Patrol)

East China Sea

Mine

Last heard from on 17 October 1944. No explanation of loss Is available from Japanese sources. No other information being available, it is presumed that ESCOLAR's loss was caused by a mine for these are known to have been present in her assigned patrol area.

39

306

TANG 1

10/24/44
(5th Patrol)

Formosa Strait

Own Torpedo

Sunk by circular run of own torpedo. See Section X for details of loss.

40

314

SHARK (II) 2

10/24/44
(
3rd Patrol)

South of Formosa

Depth Charge

Last heard from on 24 October 1944. Japanese information indicates that SHARK was probably sunk by depth charge attack south of Formosa on 24 October 1944, shortly after torpedoing a Japanese transport. It was reported that "bubbles, and heavy oil, clothes, cork, etc.," were sighted.

41

227

DARTER 1

10/24/44
(4th Patrol)

Bombay Shoal, South China Sea

Stranding

Ran aground on Bombay Shoal, South China Sea on 24 October 1944 while running surfaced at 17 knots speed. Crew abandoned ship and partial destruction was carried out by gunfire from DACE (SS247) and NAUTILUS (SS168) to prevent possible enemy utilization.

42

218

ALBACORE 2

11/7/44
(
11th Patrol)

Off Northern Honshu

Mine

Never heard from again after departing Midway on 28 October 1944. Japanese information indicates ALBACORE was sunk by mine while running submerged off northern Honshu on 7 November 1944. Both the explosion and the resulting debris were witnessed by an enemy patrol craft.

43

215

GROWLER 2

11/8/44
(11th Patrol)

Off Mindoro, P.I.

Depth Charge

Believed to have been sunk while attacking a Japanese convoy off Mindoro, P.I., on 8 November 1944. Information furnished by HAKE (SS256) and HARDHEAD (SS365), who were operating with GROWLER at the time, indicates that the loss may have occurred either as a result of enemy depth charging or the malfunctioning of one of GROWLER'S own torpedoes, but no conclusive evidence exists. No Japanese information is available.

44

277

SCAMP 5

11/9/44 to 11/16/44
(
8th Patrol)

Off Tokyo Bay

Bomb and Depth Charge

Last heard from on 9 November 1944. Japanese records list three attacks, one or more of which may possibly have accounted for loss of SCAMP while assigned to aviator rescue duty off Tokyo Bay. On 11 November 1944, a Japanese patrol plane bombed what appeared to be oil trails left by a submarine and a coast defense vessel dropped some seventy depth charges in three runs on the same target whereupon a. large oil pool was reported to have appeared. On 16 November two attacks in SCAMP's area were made, during one of which it was reported that "great explosive sounds came as a result of this attack".

45

193

SWORDFISH 3

1/12/45
(13th Patrol)

Off Okinawa

Depth Charge

Last heard from on 3 January 1945. Information furnished by KETE (SS369) indicates that SWORDFISH may have been sunk by Japanese depth charge attack near Okinawa on 12 January 1945. No explanation of loss is available from Japanese sources.

46

316

BARBEL 2

2/4/45
(4th Patrol)

Off North Borneo

Bomb

Last heard from on 3 February 1945. Japanese information indicates that BARBEL was probably sunk by aircraft attack off North Borneo on 4 February 1945. It was reported that one of the two bombs struck near the bridge.

--306-- / --307--


NO.

SS NO

NAME

DATE OF LOSS

LOCATION OF LOSS

CAUSE OF LOSS

REMARKS

NO.

47

369

KETE 5

3/20/45 to 3/31/45
(2nd Patrol)

Off Nansei Shoto Islands

Unknown

KETE had been directed to depart her patrol area in the vicinity of the Nansei Shoto Islands on 20 March and proceed to Pearl for refit. Receipt of these orders was acknowledged on 19 March and on 20 March KETE sent a. special weather report, the last message received from her. At normal cruising speed she should have arrived at Midway about 31 March 1945. No possible explanation of loss is available from Japanese sources.

48

237

TRIGGER 2

3/28/45
12th Patrol)

Off Southern Kyushu

Bomb and Depth Charge

Last heard from on 26 March 1945. Japanese records and information furnished by THREADFIN (SS410) and three other U.S. submarines indicate that TRIGGER was probably sunk as a result of a combined attack by planes and surface vessels off southern Kyushu on the afternoon of 28 March 1945. The Japanese report stated "Found oil pool of 1 x 5 miles in size the following day".

49

279

SNOOK 5

4/8/45 to 4/20/45
(9th Patrol)

South China Sea or off Formosa

Unknown

Last heard from on 8 April 1945 during rendezvous with TIGRONE (SS419) near Hainan Island in the South China Sea. No explanation of loss is available from Japanese sources.

50

371

LAGARTO 2

5/3/45
(2nd Patrol)

Gulf of Slam

Depth Charge

Last heard from on 3 May 1945. Japanese records and information furnished by BAYA (SS318) indicate that LAGARTO was probably sunk by depth charge attack In the Gulf of Siam on 3 May 1945 while attempting to attack a Japanese convoy.

51

223

BONEFISH 2

6/18/45
(8th Patrol)

Off Central Honshu, Sea of Japan

Depth Charge

Last heard from during rendezvous with TUNNY (SS282) on the morning of 18 June 1945. At this time BONEFISH received permission to conduct a submerged daylight patrol off Toyama. Wan on the west coast of Honshu and she Immediately departed for that area. Japanese information indicates that she was sunk there on 18 June as a result of depth charge attack. Wood chips and oil were observed after the attack.

52

332

BULLHEAD 2

8/6/45
(3rd Patrol)

Java Sea

Bomb

Of the many Japanese anti-submarine attacks recorded as having been made in BULLHEAD'S patrol area in the Java Sea during the period she could have been present, the one believed most likely to have accounted for her loss was that on 6 August 1945 by Japanese army planes. It was reported that two direct hits were made and that for the next ten minutes a large quantity of oil and air bubbles rose from the scene of the attack.

--308-- / --309--


Appendix III