As Europe was being pushed down the path of Total War in the late 1930s, the United States forged ahead with strengthening its various military services. This led to a period of considerable testing and growth in the field of military aviation which benefitted the classic designs of the World War 2 era (1939-1945). Bell, a relative newcomer to the field, was one of the most forward-thinking aviation concerns of the time and, while many of its designs never saw the light of day, the company certainly did its part in attempting to keep America ahead of its potential adversaries.
In November of 1939, the United States Air Corps (USAAC) set about a requirement for a single-seat, single engine fighter with performance specifications to include a speed of 425 miles per hour at 15,000 feet and a rate-of-climb of2,857 feet-per-minute. Armament would center around 4 x autocannons (or machine guns) and there would be provision for six 20lb bombs carried externally. Rough-field operations would also factor into the robust design and a mission endurance window of 1.5 hours was sought - allowing the heavy fighter to reach far-off areas or loiter when needed. All told, the requirements were considerable for the technology of the period and would require much experimentation and engineering prowess to bring such a design to fruition.
The Pratt & Whitney XH-3130 liquid-cooled inline piston engine was at the forefront of USAAC thinking to power its next-generation fighter but this engine remained developmental. Its origins lay in a United States Navy (USN) program of the late-1930s and featured 24-cylinders with and expected power output over 2,500 horsepower. In time, this engine evolved to become the larger XH-3730, though still in a developmental state, and it was thought that the engine could reach an output level of 3,000 horsepower.
The new aircraft design was collectively filed under Pursuit Specification "XC-622" and the USAAC wanted it operational as soon as 1941.
Bell began by working on their "Model 13" and this design was more or less centered on various engine installations to their P-39C "Airacobra" pusher-engined fighter. The rear-mounted arrangement of the engine helped to streamline the airframe and relieve the nose assembly of clutter, allowing a powerful armament battery to be fitted (cannon for example). The propeller was still mounted at the nose and driven by the engine through a shaft running under the cockpit floor. When this phase reached its apex, the company moved on the "Model 16" which involved an all-new airframe design.
In the Model 16 approach, a twin-boom design was selected but the rear placement of the engine was retained. The engine of choice was initially the Continental XI-1430-5 liquid-cooled inline fit set to output at 1,250 horsepower. This powerplant drove a pair of three-bladed propellers set at the rear of the fuselage in a contra-rotating arrangement. The fuselage essentially carried the engine, fuel stores, cockpit, armament and avionics fit. The wings were affixed to the rear section of the fuselage and given slight sweepback with rounded tips. The tailbooms originated from the wing's center and drove through the trailing edges, joined at the extreme aft of the aircraft by a single horizontal plane set between them. Rounded vertical tail fins were affixed to either side of this horizontal plane. Like the P-39 fighter before it, the Model 16 was to have used a tricycle undercarriage during an age when "tail-draggers" still ruled the runway.
The Army appreciated the Bell direction and eventually assigned the working designation of "XP-52" to the project. Two engine types were to be considered (Continental XI-1430 and Pratt & Whitney R-2800 "Double Wasp"). The Army began to draw up a contract to cover the two prototypes carrying the aforementioned engine fits.
On the drawing boards, the XP-52 exhibited an overall length of over 34 feet, a wingspan of 35 feet and a height of over 9 feet. It would sit at 6,480lb on empty and 8,200lb when loaded and maximum speed from the single engine coupled to the twin-boom design was around 430 miles per hour (at 20,000 feet). The rate-of-climb was within the requirements and an operating ceiling of 40,000 thought possible. Operational range was out to 960 miles giving the aircraft a good reach.
Proposed armament for the XP-52 was 2 x 20mm cannons mounted to the nose assembly. Each of these guns were afforded 100 projectiles of ammunition for short, controlled bursts capable of bringing down any bomber of the day. Each boom lead was also intended to fit a "triple arrangement" of 0.50 caliber heavy machine guns for a total of six heavy machine guns. All told, the armament offered to the XP-52 was quite considerable by 1940 standards.
The XP-52 marked the first serious attempt by the U.S. Army to pursue a "pusher fighter". However, the service decided against furthering the project even before the end of 1940. Bell continued work on the design as the larger "Model 20" (designated by the USAAC as "XP-59"), detailed elsewhere on this site. This project, too, was shelved due to the ongoing wartime commitments for both Bell and the Army. Pusher fighters never made much headway in the war as pullers continued to dominate the skies.
The XP-52 saw official cancellation on November 25th, 1941 before the American entry into World War 2.