Subject: Number Twenty-Six in the Series--The Boeing P-26

From: [email-masked] (Joseph F Baugher)
Date: 6 Oct 92 23:39:50 GMT

>From Joseph F Baugher <[email-masked]>

The Boeing P-26 was an interesting mixture of the old and the new.  It 
was the first production monoplane fighter and the first all-metal 
fighter to serve with the USAAC.  It was also the last USAAC fighter 
to have externally-braced wings, an open cockpit, and non-retractable 
undercarriage.  For Boeing, it was also their last production fighter, 
and it brought to an end the fifteen-year period during which Boeing 
dominated the market for fighters for both the Navy and the USAAC.  

In the early 1930s, the USAAC was faced with a new generation of 
monoplane bombers which were faster than its current stable of biplane 
fighters.  In September 1931, the USAAC approached Boeing engineers 
with a requirement for a monoplane fighter that would be faster than 
the most up-to-date bombers that were flying at the time.  Initial 
work on the project was begun at Boeing expense that very month.  The 
company designation for the project was Model 248.  On December 5, 
1931, Boeing and USAAC signed a bailment contract for three prototypes 
for a monoplane fighter.  The experimental designation of XP-936 was 
applied.  Under the terms of the agreement, Boeing would provide the 
airframe, but the Army would provide the engines and the instruments.  
Boeing would retain ownership of the airframes.  

The design progressed rapidly, and actual construction of the Model 
248 began in January of 1932.  The design which finally emerged was a 
compromise between the advanced ideas of Boeing and the conservative 
and careful approach favored by the USAAC.  It was a look forward and 
a look backward.  

The Model 248 (XP-936) was an all-metal low-wing monoplane with 
wire-braced wings (a cantilever wing was rejected as not being strong 
enough for a fighter).  The wing was of low aspect ratio with a thin 
section.  The wing had two main spars, built up of sheet and angle 
duralumin.  The wing supported dural ribs, to which was riveted a 
series of closely-spaced spanwise stringers which supported the metal 
skin.  The use of external wire bracing for the wing would at first 
sight seem to have been a retrograde step, however the use of wire 
bracing for the wing permitted a lighter wing structure.  Even so, 
wires produced less drag than would have been produced by the use of 
rigid struts.  The horizontal tailplane, unlike the wing, was of fully 
cantilever construction.  

The fixed, non-retractable undercarriage would also seem to have been 
a retrograde step.  The fixed undercarriage did indeed add extra drag, 
but it had an advantage in reducing weight and structural complexity 
and it provided a structurally efficient low anchor point for the 
flying wires.  The rear portion of each undercarriage unit consisted 
of an inverted tubular bipod fastened to the front and rear wing 
spars.  The flying wires were attached to the apex, and the wheel 
pivoted about the apex on an arm, with the landing loads being 
absorbed through a shock absorber strut connecting the wheel axle to 
the front spar.  The entire lower portion of the undercarriage was 
enclosed by streamlined wheel fairings.  A tailwheel took the place of 
the traditional skid.  Wheel brakes were provided.  

The fuselage was of a semi-monocoque type with aluminum bulkheads, 
hat-section longerons, skin stiffeners and skin.  The aircraft was to 
be powered by the well-proven Pratt and Whitney R-1340-9 nine-cylinder 
radial (no experimenting with untried engines this time!).  A 
Townend-type drag ring was fitted around the engine.  Armament was 
provided by one 0.50-in and one 0.30-in machine guns, or two 0.30-in 
machine guns, mounted in the fuselage sides and firing through the 
engine cylinder banks.  Under-fuselage racks were fitted which could 
carry five 30-lb bombs or two 122 lb bombs.  

The first XP-936 made its maiden flight on March 20, 1932.  The design 
had progressed from drawing board to first flight in only 9 weeks, 
which was a remarkable feat for a major USAAC fighter project.  It was 
immediately sent to Wright Field for Army evaluation.  The second 
XP-936 had been completed and delivered to Wright Field before the 
first machine had made its maiden flight.  It was later flown to 
Anacostia, Maryland, for demonstration to the Navy.  It was then 
returned to Wright Field, where it underwent a series of static tests 
by the Army.  On April 25, the third XP-936 was sent to Selfridge 
Field, Michigan, for service testing with active squadrons While 
undergoing tests at Wright Field, the XP-936 weighted 2119 lbs empty 
and 2789 lbs loaded.  Maximum speed was 227 mph at 10,000 feet, 210 
mph at 20,000 feet, and 174 mph at 27,800 feet, the aircraft's service 
ceiling was 28,900 feet.  Initial climb rate was 2260 feet per minute. 
Range was 758 miles.  

It is interesting to compare the general performance of the XP-936 
with that of the P-12F biplane, which was still in production at the 
time the XP-936 was delivered.  The XP-936 had a slightly later 
version of the same engine that powered the P-12F, and the engine gave 
the monoplane only a 20 hp power advantage over its biplane 
predecessor.  The XP-936 was only 39 lbs heavier than the P-12F but 
was 27 mph faster and outclimbed it by a rate of 476 ft/min.  However, 
the P-26 fell 800 feet short of the biplane's absolute ceiling.  

The Army bought the three XP-936s on June 15, 1932, assigning them the 
designation XP-26.  Serials were 32-412/414.  The designation was soon 
changed to the service test designation of Y1P-26 and eventually to 
plain P-26.  However, these planes never entered squadron service with 
the USAAC.  

Before service testing on the XP-936 were completed, the Army decided 
to go ahead with production of the design in an improved form.  On 
November 7, 1932, the Army issued a new specification for a fighter 
which incorporated the best features of the Model 248 with the 
improvements found desirable during the test program.  On January 11, 
1933, USAAC ordered 111 examples under the designation P-26A.  Serials 
were 33-28/138.  It beat out the competing Curtiss XP-31 Swift for 
production orders.  This initial order was soon increased to 136, with 
the additional planes being completed as P-26B and P-26C.  This was 
the the largest order placed for a single aircraft type since the 
Boeing MB-3A of 1921.  

The first P-26A made its maiden flight on January 10, 1934, and the 
last aircraft of the initial order for 111 aircraft was delivered on 
June 30, 1934.  The factory designation of the P-26A was Model 266.  
The unit price per plane (less engine and government- furnished 
equipment such as armament, radio, etc) was $9999, compared with 
$10,197 for the P-12E biplane which it replaced.  This must have been 
one of the few occasions in history in which a new military aircraft 
was actually cheaper than the one which it superseded.  :-) 

The powerplant of the P-26A was a single Pratt and Whitney R-1340-27 
Wasp radial engine rated at 500 hp at 7500 feet.  It drove a 
Hamilton-Standard two-blade, adjustable-pitch propeller.  The armament 
was the same as that of the prototypes, namely a pair of 0.30-in 
machine guns, or one 0.30 and one 0.50-in machine guns, mounted in the 
fuselage sides and firing through the spaces between the cylinder 
heads of the radial engine.  Outwardly, the P-26A differed from the 
prototypes only in that the wheel pants did not project aft of the 
undercarriage strut fairings.  Inwardly, the P-26A wing structure was 
considerably revised and a radio was added.  The addition of the radio 
was reflected in the fitting of an antenna mast on the starboard 
fuselage just ahead of the cockpit and a mast on top of the vertical 
tail.  Emergency flotation gear was added, which consisted of 
inflatable air bags mounted externally above the wing root.  

Originally, the P-26As had the low streamline headrests of the 
prototypes, but these were soon increased in height by 8 inches for 
pilot protection after one of the early models flipped over on its 
back following a landing on soft ground and killed the pilot without 
seriously damaging the airplane.  Delivery of later production 
machines was delayed until this modification was completed.  

The P-26A had a maximum speed of 234 mph.  Range was 635 miles, and 
initial climb rate was 2360 ft/min.  Service ceiling was 27,400 feet, 
and absolute ceiling was 28,300 feet.  Weights were 2197 lbs empty, 
2955 lb gross.  Armament of the P-26A was the same as that of the 
prototypes, namely one 0.50-in, one 0.30-in machine guns, or two 
0.30-in machine guns mounted in the fuselage sides firing through the 
engine cylinder banks.  Racks were provided under the fuselage for 
five 30-lb bombs or two 100-lb bombs.  

After the P-26As were in service for a short time, the Army became 
dissatisfied with the relatively high landing speed of 82.5 mph.  Wing 
flaps were developed and tested by the Army on a P-26A and by Boeing 
on the Model 281, the export version of the P-26A.  These brought the 
landing speed down to 73 mph.  Boeing then retrofitted these flaps to 
all P-26As then in service and also added them on all the P-26Bs and 
Cs still in the factory.  

The first units to take delivery of P-26s belonged to the 20th Fighter 
Group (55th, 77th, and 795h Squadrons) based in Louisiana, which kept 
them until 1938.  Other units to operate the P-26 were the First 
Fighter Group (17th, 27th, and 94th Squadrons) based in Michigan, 
which kept them until 1938-41.  They were in service with the 17th 
Fighter Group (34th and 95th Squadron) in California for only a year.  
These planes were subsequently transferred to the 16th Fighter Group 
(24th, 29th, and 78th Squadrons) in the Canal Zone and in Hawaii where 
they served until 1938.  P-26s were also flown by the 6th and 19th 
squadrons of the 18th fighter group based in Hawaii from 1938 onward.  
They were also flown by the 28th, 39th, and 31st Squadrons of the 37th 
Fighter Group based in Panama in 1940, and by the 32nd Group from 
bases in Panama in 1941.  They were also flown by the 3rd Squadron in 
the Philippines.  

Two of the 25 aircraft added to the initial P-26A order (Ser Nos 
33-179,180) were completed as P-26Bs.  They differed from the P-26A in 
being fitted with 600 hp Pratt and Whitney SR-1340-33 fuel injected 
engines.  The attendant revisions to the fuel system, plus the fact 
that the P-26Bs were the first P-26s built with wing flaps as original 
equipment, justified a change in factory model designation to Model 
266A.  The first flight of a P-26B was on January 10, 1935.  The first 
P-26B was delivered to the Army on June 20, 1935, the second on June 
21.  Empty weight was 2302 lbs, gross weight was 3060 lbs.  Maximum 
speed was 235 mph.  Range was 635 miles.  Initial rate of climb was 
2360 ft/min.  Service ceiling was 27,000 feet.  Absolute ceiling was 
28,000 feet.  

It had been originally planned for all 25 planes of the add-on order 
to be completed as P-26Bs.  Unfortunately, there were delays in the 
production of the Pratt and Whitney fuel-injected Wasp engines.  
Consequently, twenty-three of the 25 aircraft added to the original 
order for 111 P-26As were built as P-26Cs.  These differed from the 
P-26A only in slight differences in the fuel and carburetion systems.  
The engine was the SR-1340-27.  The differences were so slight that 
the factory model number was not changed.  Serials were 33-181, 
22-183/203.  The first P-26C was delivered on February 10, 1936, and 
the last on March 7, 1937.  After about a year in service, all of the 
P-26Cs were converted to P-26B standards (Boeing 266A) by the 
installation of fuel injection engines and revision of the fuel system 
and its controls.  

The Model 281 was the export version of the P-26A.  It differed only 
in the details of military equipment.  The first flight of the Model 
281 took place on August 2, 1934, and early tests indicated that the 
landing speed was too high for the small grass strips from which the 
fighter would be expected to operate.  Split-type wing flaps were 
developed and installed, and were tested by the Army for comparison 
with experimental flaps that the Army had installed on a standard 
P-26A.  As a result of these tests, all P-26As were returned to the 
factory for installation of the new flaps, as previously described.  

One Model 281 was sold to Spain, and eleven were shipped to China.  
Deliveries to China began on September 15, 1934.  The last was shipped 
on January 16, 1936.  The engine was the Pratt and Whitney R-1340-33.  
Maximum speed at 6000 feet was 235 mph.  Initial climb rate was 2210 
feet per minute.  One Chinese squadron operating the Model 281 saw 
continuous action against Japanese invaders, and a considerable number 
of kills were registered.  On August 20, 1937, eight of these fighters 
engaged six Mitsubishi G3M2 bombers during a raid on Nanking and 
destroyed all of them without lost to themselves.  However, the Model 
281 fighters were eventually forced out of service through lack of 
spares.  

The P-26 was a popular pilots' airplane and performed well until 
outclassed by more modern fighters.  P-26s served in front-line units 
with the USAAC until 1938-40, when they began to be replaced by 
Seversky P-35 and Curtiss P-36A fighters.  All P-26 models had been 
withdrawn from regular squadron use by the time of Pearl Harbor.  Most 
surviving stateside aircraft had been relegated to mechanic training 
schools.  Most of those P-26s that had been stationed overseas were 
sold to the governments of the Philippines and Panama, and two were 
sold to Guatemala.  Some of these P-26s were serving with the 
Philippine Air Force at the time of the Japanese attack.  One of the 
Philippine P-26s is credited with shooting down the first Japanese 
plane during the early attacks on the islands.  However, the few P-26s 
operated by the Philippine Army Air Force were quickly overwhelmed by 
the onslaught of the Japanese Zero fighters.  

Several of the Panamanian P-26s were later acquired by Guatemala and 
were still active as trainers as late as 1957.  One P-26 was obtained 
from Guatemala by the Planes of Fame museum of Chino, California where 
it has been restored to flying condition in its original US Army 
markings.  Another was obtained from the same source by the National 
Air and Space Museum of the Smithsonian Institution.  

Sources: 

  Boeing Aircraft since 1916, Peter M.  Bowers, Naval Institute Press, 
  1989.  

  "The Boeing P-26A", Peter M.  Bowers, in "Aircraft in Profile", 
  Doubleday, 1969.  

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

  The American Fighter, Enzo Angellucci and Peter Bowers, Orion Books, 
  1987.  

Joe Baugher       AT&T Bell Laboratories    2000 North Naperville Road 
		  Naperville, Illinois 60566-7033.   (708) 713-4548