Article 12173 of rec.aviation.military:
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From: jfb@usgp1.ih.att.com (Joe Baugher)
Subject: Bomber Series--North American B-25 Mitchell (17 of 32)
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Summary: B-25J
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Date: Fri, 3 Feb 1995 16:34:47 GMT
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The B-25J (NA-108) was the final production version of the Mitchell.  
It was also the version of the Mitchell to be built in the largest 
numbers, a total of 4318 being built.  It was manufactured exclusively 
at North American's Kansas City plant, the Inglewood plant having 
switched over to the manufacture of the P-51 Mustang fighter after the 
last B-25H had been delivered.  

Kansas City briefly built both the B-25D and J at the same time, the 
first J being accepted in December 1943 and the last D in March of 
1944.  

The B-25J returned to its primary function as medium bomber, and 
reverted to the transparent, bombardier-equipped nose of the earlier 
B-25C and D.  The tail gun position with the deeper rear fuselage, the 
bay-window mounted waist guns, and the forward-mounted dorsal turret 
that had been introduced on the B-25H were all retained on the B-25J.  
The blister gun packs on the sides of the forward fuselage of the 
later versions of the B-25H were also retained.  However, the copilot 
position (which had been omitted on the B-25H) was restored.  The crew 
was now six--pilot, co-pilot, navigator/bombardier/gunner, turret 
gunner/engineer, radio operator/waist gunner, and tail gunner.  The 
bomb racks and bomb bay doors were now all electrically-operated.  A 
50,000 BTU surface combustion heater was provided at the waist gun 
station.  Provision was made to carry three 1000 pound bombs rather 
than just two.  Alternatively, two 1600-pound armor-piercing bombs 
could be carried.  Provisions were made for the carrying of six 
325-pound depth charges on underwing racks.  

The first B-25J (43-3780) took off on its first flight in October 
1943, piloted by Joe Barton.  The first USAAF acceptance took place 
before the end of the year.  

The B-25J was built in eight main production blocks (-1, -5, -10, -15, 
-20, -25, -30, -35), with different suffix numbers being allocated to 
significant modifications, including -11, -17, -22, -27, -32, and -37.  
Many of these modifications involved the replacement of the 
transparent nose by a solid nose armed with eight fixed machine guns.  

Beginning with the 151st B-25J-1 (43-4019), provisions for the 
carrying of a single 2000-pound bomb were deleted.  As it turned out, 
the 2000-pound bomb was only rarely carried during actual combat, and 
the bulky and restrictive shackles for the 2000-pound bomb took up a 
lot of space in the bomb bay.  This enabled a normal offensive load of 
two 1600-lb or three 1000-lb bombs to be carried internally, plus 
combinations of smaller bombs of various types, including 20-pound 
parafrags.  

The -5 production block introduced a revised braking system control 
cable.  The N-3C gunsight replaced the N-3B sight and A-1 bombing 
head.  De-icing windshield panels were installed, and gun-blast 
arrestors were installed on top turret guns and on side fuselage 
blister guns.  

The -10 production block introduced the mounting lugs and controls for 
underwing bombs.  Electric bomb racks were provided.  The heaters at 
the waist gun positions were found to be inefficient and were removed.  

The -15 production block had N-8A optical gunsights installed on the 
flexible waist guns.  Provisions for ring and bead sights were 
provided for the flexible nose gun.  

The -20 production block introduced some revisions to the cabin 
heating system with a 50,000 BTU/hour heater.  A second 0.50-inch 
fixed machine gun was installed in the nose.  The flexible nose gun 
was relocated 4 inches higher.  Additional armor protection was 
provided in the floor of the nose for the bombardier.  The top turret 
canopy was reinforced for greater strength, and a hydraulic emergency 
brake system was incorporated.  Beginning with 44-29304, a change was 
made to the Holley 1685RB carburetor.  

The -25 production block introduced new types of armored seats for 
both pilots.  Beginning with 44-30111, armored plate deflectors were 
added to the upper fuselage to prevent the upper turret gunner from 
inadvertently firing his guns into the structure of his own plane, 
especially into the raised cupola where the tail gunner sat.  
Beginning with 44-30309 and throughout the -25 production block, 
provisions were made for the mounting of a chemical tank on an 
underwing bomb rack.  

On production block -30, stainless steel "S"-shaped exhaust stacks 
replaced the enameled 1020 steel stacks on cylinders 1, 7, and 9.  
Effective with serial number 44-31111, provisions were made for the 
mounting of a chemical tank on an underwing bomb rack.  Provisions for 
a type C-6 electric bomb hoist were made effective with 44-31311.  
Provisions were made for the carrying of wing-mounted T-64 zero-length 
rocket launchers beginning with 44-31338.  These launchers could carry 
up to eight five-inch high-velocity aircraft rockets (HVAR).  
Beginning with 44-31491, a K-10 computing gunsight was provided for 
the gunner in the tail turret, and M-8A gun mounts were provided for 
the tail guns.  Provisions for the mounting of glide bombs suspended 
underneath the fuselage were added beginning with 44-86692.  In 
addition, a special cockpit sight and release controls for the glide 
bomb were provided.  An N-9B bombsight was installed beginning with 
44-86793.  Beginning with 44-86799, the rudder control cables were 
rerouted.  

The -35 production block introduced provisions for the carrying and 
laying of aerial mines.  

Some of the B-25Js ended up with training units, but most were issued 
to units in action in the Southwest Pacific.  The first B-25Js arrived 
at Townsville and Nadzab depots in the summer of 1944.  They were 
issued to the 38th Bombardment Group.  The 345th BG received its 
B-25Js in September.  Despite volume production, it was hard to meet 
the demand, and the 42nd Bombardment Group did not get its B-25Js to 
replace its aging C and D models until late 1944.  

In the Mediterranean theatre, the B-25J was issued to operational bomb 
groups on an as-required basis.  In April 1944, the 310th Bombardment 
Group based on Corsica received its first B-25Js.  The remaining 
groups in the 57th Bombardment wing of the 12th Air Force transitioned 
to the B-25J throughout the remainder of 1944.  

The US Marine Corps ordered 255 B-25Js under the designation PBJ-1J.  

The transparent nose with its bombardier could be replaced at the 
factory by a solid nose that was equipped with eight 0.50-inch machine 
guns.  With this modification, the aircraft was designated as 
B-25J-11, -17, -22, -27, -32, or -37, depending on which production 
block the modification took place.  With its maximum armament of 
eighteen guns, the solid-nosed B-25J was the most heavily-armed attack 
aircraft in the Allied arsenal.  Sometimes, however, the package guns 
on the sides of the fuselage were deleted, the remaining fourteen guns 
being more than enough.  

The last B-25J was delivered to the USAAF in August of 1945.  The day 
after the war in the Pacific ended, the Kansas City plant was closed.  

Serial numbers of B-25J:

43-3870/4104		North American B-25J-1 Mitchell
				c/n 108-24196/108-22430
43-27473/27792		North American B-25J-1 Mitchell
				c/n 108-34486/108-34805
43-27793/28112		North American B-25J-5 Mitchell
				c/n 108-34806/108-35125
43-28113/28222		North American B-25J-10/11 Mitchell
				c/n 108-35126/108-35235
43-35946/36245		North American B-25J-10/11 Mitchell
				c/n 108-35236/108-35535
44-28711/29110		North American B-25J-15/17 Mitchell
				c/n 108-31986/108-32385
44-29111/29910		North American B-25J-20/22 Mitchell
				c/n 108-32386/108-33185
44-29911/30910		North American B-25J-25/27 Mitchell
				c/n 108-33186/108-34185
44-30911/31510		North American B-25J-30/32 Mitchell
				c/n 108-36986/108-37585
44-86692/86891		North American B-25J-30/32 Mitchell
				c/n 108-47446/108-47645
44-86892/86897		North American B-25J-35/37 Mitchell
				c/n 108-47646/108-47651
45-8801/9242		North American B-25J-35/37 Mitchell
				c/n 108-47652/108-47750
45-9000/9242 		cancelled contract for B-25J-35 Mitchell


Specification of the North American B-25J Mitchell:  

Two Wright R-2600-13 Double Cyclone fourteen-cylinder air-cooled 
radials, rated at 1700 hp each for takeoff and 1500 hp at 2400 rpm.  
Equipped with Holley 1685HA carburetors.  
Performance:  Maximum speed 275 mph at 15,000 feet.  230 mph cruising 
speed.  Initial climb rate 1110 feet per minute.  An altitude of 
15,000 feet could be reached in 19 minutes.  Service ceiling 24,000 
feet.  Range 1275 miles with 3200 pounds of bombs.  Ferry range 2700 
miles.  
Dimensions:  Wingspan 67 feet 6.7 inches, length 53 feet 5.75 inches 
(bomber version), height 16 feet 4.2 inches, wing area 610 square 
feet.  
Weights:  21,100 pounds empty, 33,000 pounds normal loaded, 35,000 
pounds gross, 41,800 pounds maximum overload.  
Fuel:  The fuel capacity consisted of four tanks in the inner wing 
panels, with a total capacity of 670 US gallons.  In addition, 304 US 
gallons of fuel could be carried in auxiliary tanks in the outboard 
wing panels, for a normal total fuel load of 974 US gallons.  A 
515-gallon tank could be installed in the bomb bay for ferrying 
purposes, 125 gallons of fuel could be carried in side waist 
positions, a 215-gallon self-sealing fuel tank installed in the top of 
the bomb bay, and provisions could be made for a droppable 335-gallon 
metal bomb-bay fuel tank.  
Armament:  
Medium bomber version:  
One flexible 0.50-inch machine gun in nose, 300 rounds.  One fixed 
0.50-inch machine gun in nose, 300 rounds.  Beginning with B-25J-20, a 
second fixed 0.50-inch gun was added in the nose.  
Strafer version:  
Eight 0.50-inch machine guns in the nose with 400 rpg.  
All versions:  
Two 0.50-inch machine guns in individual blisters on each side of
the forward fuselage with 400 rpg.  Two 0.50-inch machine guns in top 
turret, 400 rpg.  Two 0.50-inch machine guns in waist position, 200 
rpg.  Two 0.50-inch machine guns in tail turret, 600 rpg.  

Normal bomb load was 3000 pounds, but a maximum bombload of 4000 
pounds could be carried on short-range missions.  Some had underwing 
racks for eight 5-inch high velocity aircraft rockets (HVARs).  

Sources:

   B-25 Mitchell: The Magnificent Medium, N. L. Avery, Phalanx, 1992.

   Medium with the Mostest--The B-25 Mitchell, Jerry Scutts,
   Air International, Vol. 44, Nos 2 and 3, 1993.

   Boston, Mitchell, and Liberator in Australian Service, Stewart
   Wilson, Aerospace Publications, 1992.

   Famous Bombers of the Second World War, William Green, Doubleday,
   1959.

   North American's Flying Gun--The Story of the B-25 From Paper
   Airplane to Legendary Bomber, Jack Dean, Wings, Vol 23 No 4, 1993.

   United States Military Aircraft Since 1909, Gordon Swanborough
   and Peter M. Bowers, Smithsonian, 1989.

   United States Navy Aircraft Since 1911, Gordon Swanborough and
   Peter M. Bowers, Naval Institute Press, 1990.

   Jane's American Fighting Aircraft of the 20th Century, Michael J.
   H. Taylor.


Joe Baugher			  **************************************
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