Ground-Breaking Design Hampered by Government Worrying
By Sean Sims
The Boeing Airplane Company was formed by William Boeing in 1916. Three years later they secured their first large military contract when the U.S. Army Air Corps ordered 200 Boeing MB-3A fighter aircraft. The Boeing MB-3A was an improved version of the Thomas Morse MB-3 fighter. Boeing added a welded steel-tube fuselage (instead of the original Thomas Morse designed wooden fuselage), improved radiators, and a redesigned tail. Through the high-quality work Boeing put in to the MB-3A they went on to produce many more aircraft for the United States while Thomas Morse faded into history.
The next fighter off the Boeing production line was the Model 15 design. This aircraft sported a welded steel-tube fuselage and wooden wings. It was powered by a Curtiss D-12 435-hp liquid-cooled engine. In 1923 Boeing lucked out when the U.S. Army Air Corps (USAAC) purchased 30 Model 15 aircraft, known as the PW-9 (pursuit, water-cooled) and the U.S. Navy (USN) purchased 14 aircraft, known as the FB-1 (fighter, Boeing).
With two wins under their belt the Boeing Airplane Company went on to produce an unbroken series of numerous additional fighter aircraft until the P-26 Peashooter.
Origins of the Peashooter
In 1931 Boeing developed a twin-engine bomber for the USAAC designated the B-9; the first in a long line of Boeing bomber aircraft. This aircraft was a derivative of the Boeing Monomail. The Monomail was developed by Boeing Air Transport (which would eventually become United Airlines), an airline subsidiary of the Boeing Aircraft Company, in 1930 for use as a high-speed mail delivery aircraft.
Officially known as the Boeing Model 200 Monomail, a cantilevered, low-wing monoplane with an aluminum monocoque fuselage and retractable landing gear. The aircraft was 41-ft long with a 52-ft wingspan and could achieve 158-mph flight carrying 2,300-lb of cargo/passengers over a 600-mi range. The Boeing Aircraft Company went on to derive additional civilian aircraft from the Monomail design. These new designs continued to build Boeing’s experience all the way to the Boeing 777 airliner.
The B-9 was not the first monoplane bomber design. The Douglas B-7 and Fokker (General Aviation) XB-8 were both monoplanes but utilized wood and fabric construction whereas the B-9 was all metal. The B-9 design, based on the Monomail, achieved a top speed of 186-mph. This was faster than the current “top of the line” fighter, Boeing’s own P-12 (USAAC)/F4B (USN). The B-9 first flew on 29 April 1931. Later that year, in September, the USAAC asked Boeing to design a fighter capable of overtaking the current bomber aircraft available worldwide.
Rapid Development of a Groundbreaking Design
Boeing Model 248, which would become known as USAAC XP-936, was developed as an all metal, low-wing monoplane with the instruments and engine provided by the USAAC. The X-series designators were assigned to projects built by private companies that used some Army-owned equipment; the instruments and engine in this case.
The XP-936 design was forced to incorporate a few design elements demanded by the USAAC. Despite Boeing’s success with the Monomail and it’s cantilevered wings and retractable landing gear, the USAAC required external wire bracing and fixed landing gear. The wire bracing as added for fear the wings would fail during rigorous flight maneuvers typical of fighter aircraft. The fixed landing gear were required for two reasons: 1) it was believed any reduction in aerodynamic drag was offset by the added weight of the retraction mechanism. 2) early retractable landing gear suffered frequent malfunctions and required manual activation. The XP-936 prototype first flew on 20 March 1932 an astonishing nine weeks after the design process had started.
The XP-936 was outfitted with one 50-caliber machine gun and one 30-caliber machine gun or dual 30-caliber machine guns with 200 rounds each. The machine guns were mounted in the side of the fuselage at the floor of the cockpit and firing through the engine cylinder banks. An additional five 30-lb bombs, two 122-lb bombs or two parachute flares could be mounted between the landing gear. This armament would prove to be woefully inadequate.
All three XP-936 prototypes were built in a three month span. Extensive testing occurred for the remaining eight months of 1932. The XP-936 was competing against a similar design from Curtiss known as the XP-31 (XP-934) Swift. The Swift first flew in July of 1932 with the main difference from the XP-936 being an enclosed cockpit (the first designed into a fighter). By the time the prototype was delivered to the USAAC on 1 March 1933 it has already lost to the XP-936. The one and only copy ever built was scrapped in 1935.
Initially, the XP-936 had a high landing speed of 82-mph which was 17-mph faster than the P-12F (the current top fighter aircraft). The high landing speed combined with the narrow-tracked landing gear contributed to numerous landing accidents. This led the USAAC to ask Boeing to add flaps which reduced the landing speed to 73-mph. The P-26 would become the first USAAC production aircraft ever outfitted with flaps.
One other major design change occurred after a fatal landing accident killed a test pilot. The aircraft flipped on its back and the pilot’s neck was broken. Aircraft designers at the time had always relied on the top wing of a biplane to protect the cockpit in the event of a flip. The headrest of the XP-936 was extended an additional eight inches and resembled the rollbar on an open wheel racecar.
On 15 June 1932 the USAAC bought the three prototypes from Boeing and assigned the XP-26 designation. The designation was subsequently changed to the service test designation of Y1P-26 and eventually to just P-26. The three prototypes were exclusively used for testing through the remainder of 1932. At that time the USAAC ordered Boeing to begin producing the fighter.
In the meantime, the USAAC ordered an additional 25 Boeing P-12F biplane fighters. The P-12F and XP-26 are both powered by the same 600-hp Pratt and Whitney engine. The tradeoffs between a monoplane and biplane design were easy to determine. The XP-26 achieved a top speed of 234-mph which was 20% faster than the P-12F and it also had a range of 375-mi which provided 75 additional miles over the biplane. But the P-12F knocked the socks off the XP-26 with a climb rate of 2,920-ft/min which was 24% greater than the XP-26 and it also boasted a service ceiling of 31,400-ft soaring 4,000-ft higher than the monoplane.
The Peashooter Production Line Begins
On 11 January 1934 the USAAC ordered 111 P-26A aircraft from Boeing. This order was placed prior to the completion of formal USAAC testing completion of the XP-936. The P-26A, Boeing Model 266 (after the numerous revisions), first flew exactly one year later on 10 January 1934.
The P-26A featured a revised Pratt and Whitney R-1340-27 Wasp nine-cylinder supercharged 500-hp radial engine with a two-blade adjustable-pitch Hamilton-Standard propeller. The order was subsequently increased to 136 aircraft with the additional aircraft being built at P-26B or P-26C models. Two P-26B aircraft were produced with the Pratt and Whitney SR-1340-33 600-hp fuel injected engine. The P-26C aircraft utilized the Pratt and Whitney R-1340-27 carbureted engine. All but six P-26C aircraft were converted to P-26B by installing fuel injection engines after roughly one year in service. In total the USACC acquired 139 Peashooter aircraft (including the three prototypes) from 1933 to 1934. This was the largest single aircraft type order placed since the Boeing MB-3A in 1921.
The standard paint scheme at the time included yellow wings and a blue fuselage. The Peashooter was no different but added a blue vertical stripe on the leading edge of the tail with alternating horizontal red and white stripes on the rudder. The wings and fuselage also featured colored stripes denoting the aircraft’s position in the formation. The aircraft also featured squadron and group markings. Of particular interest, the aircraft assigned to the 34th Pursuit Squadron (the present day 34th Bomb Squadron), 17th Pursuit Group based at March Field, California were the original “Thunderbirds” and an early version of the famous insignia adorned their aircraft 13 years before the team of today was formed.
P-26s Around the World
An export version of the P-26A was created under Boeing Model 281. The only difference was the removal of military equipment. The first flight of the Model 281 occurred on 2 August 1934. Again the landing speed was determined to be too high and a new type of split flaps were installed. The USAAC liked the new flaps and returned all P-26As to the factory to be retrofitted. The export variant was widely employed and saw combat with the Republic of China Air Force and the Philippine Army Air Corps.
In 1942 the Guatemalan Air Force acquired seven P-26s when the U.S. government smuggled them into the country as Boeing PT-26A training aircraft. The PT-26A designation belonged to the Fairchild Cornell primary trainer. This bypassed a Congressional rule forbidding export of fighter aircraft to all Latin American nations except Brazil and Mexico. The final P-26 in American service was transferred to Guatemala on 4 May 1943. The P-26s remained in service with Guatemala through 1957 when they were replaced with P-51 Mustangs.
P-26 Sunset
The Peashooter quickly became obsolete due to rapid developments in aviation during the 1930s and 1940s. For example, a mere three years after the P-26’s first flight, in 1935 the Curtiss P-36 Hawk, Messerschmitt Bf 109 and Hawker Hurricane were all flying with enclosed cockpits, retractable landing gear and cantilever wings. Twenty-two U.S. squadrons continued to receive and fly the Peashooter through 1938.
At that time the P-26 was phased out in favor of the Seversky P-35 (with an interesting history as well) and Curtis P-36 Hawk (the predecessor to the Curtis P-40 Warhawk). The P-35’s claim to fame is the first single-seat fighter featuring all-metal construction, retractable landing gear and an enclosed cockpit.
The features Boeing was forced to include in the Peashooter design would ultimately doom its existence. The P-26 was unable to keep up with the P-35 or P-36 due to the streamlined designs they employed. The end of the Peashooter culminated a 15-yr period of Boeing dominance for U.S. fighters. It was the last production fighter from Boeing until they bought McDonnell Douglas in 1997 and acquired production and support for the F/A-18 Hornet family.
Boeing attempted to revive the Peashooter with an improved version designated the P-29 in 1934. The prototype was designated YP-29 and featured a fully cantilevered wing, retractable landing gear and enclosed cockpit. The aircraft did not achieve significant performance gains. The USAAC did not see value in disrupting the Boeing production line to switch to the YP-29 and the project was scrapped.
Remaining Peashooters
Only two original Peashooters remain today. One is airworthy and is owned by the Planes of Fame Air Museum in Chino, California. The P-26A, serial number 33-123, is regularly featured in the annual Planes of Fame Air Show and was obtained from Guatemala. The second original aircraft is owned by the National Air and Space Museum. The P-26A, serial number 33-135, was also obtained from Guatemala and is on display at the Steven F. Udvar-Hazy Center in Chantilly, Virginia in the 34th Pursuit Squadron “Thunderbirds” livery.
Three reproductions are on exhibit with two additional replicas under construction.
A P-26A replica is on display at the National Museum of the U.S. Air Force in Dayton, Ohio.
A XP-936 replica is on display at the San Diego Air and Space Museum in San Diego California.
A P-26 replica is owned by the Military Aviation Museum in Virginia Beach, Virginia.
The MAM P-26 may be made airworthy in the future. The MAM indicates a new set of wings would need to be constructed. Two P-26A aircraft are being constructed by Golden Age Aeroplane Works in Seymour, Indiana. The intent is to build airworthy replicas of the Peashooter. The project has been on-going since 1991.