The Curtiss XP-55 Ascender was an unusual tail first fighter that reached the prototype stage, but that proved to be inferior to more conventional fighter designs.
In 1939 the Army decided to break with its normal pattern of asking for incremental improvements in aircraft design and instead hold a contest looking for more radical designs. On 27 November 1939 they issued a specification for a new fighter using the Pratt & Whitney X-1800 A3G engine. The new aircraft was to have low drag, exceptional pilot visibility and heavy fire power. Both conventional and experimental designs were welcome.
On 20 February 1940 the Army issued ‘Request for Data R40-C’, calling for an experimental aircraft. This produced three designs – the Consolidated Vultee XP-54, Northrop XP-56 and Curtiss XP-55. All three of these designs produced flying aircraft, although none of them resulted in production aircraft.
The Curtiss design used a canard configuration, with the main wings at the rear and small control surfaces at the nose. The main wing was swept back, had ailerons, trailing edge flaps and vertical fins and rudders above and below the wing tips. The small ‘wing’ at the nose had elevators on their trailing edge. The full version had an oval section fuselage of all metal construction. It was the first Curtiss design to use a tricycle landing gear. All three of the experimental aircraft were pusher designs, with the propeller at the rear. In the case of the XP-55 the nose was used to carry four 0.5in machine guns.
On 20 June 1940 Curtiss were given a contract to produce a wind tunnel test model and more data, with an option for a prototype if the Army was interested. However they soon decided that the Curtiss design was less interesting that the other two, and didn’t take up the option for a prototype. Curtiss was still convinced, and so the company used its own money to build a full scale flying test-bed (the Model CW-24B). This had wooden wings, a fabric covered welded steel tube fuselage and was powered by a Menasco C6S-5 Buccaneer engine, of around 275hp. When it was first built, this aircraft had its vertical fins about half way along the wings.
At the end of 1941 mock-up went to the Muroc Dry Lake test site for trials, making its maiden flight there on 2 December 1941. It took part in over 160 test flights. These revealed serious stability problems, which were partly solved by moving the vertical fins nearer to the end of the wings.
On 10 July 1942 Curtiss was given a contract for three prototypes. By this point the X-1800 engine had failed, so they were to use the proven 1,475hp Allison V-1710-F23R instead.
The first prototype (42-78845) was delivered on 13 July 1943 and made its maiden flight on 19 July 1943. It was found that the aircraft had to reach unacceptably high speeds on the runway before the small elevators became effective. This prototype was lost during spin tests at St. Louis on 15 November, after it had dropped 16,000ft out of control, although the test pilot escaped safely.
The second prototype (42-78846) was completed to almost the same design, and made its maiden flight on 9 January 1944. It was flown conservatively until more work could be done to solve the spin problems. It was later given the modifications introduced on the third prototype. This aircraft has survived and is at the Smithsonian.
The third prototype made its maiden flight on 25 April 1944. This aircraft was completed with 4ft wider wings with ‘trailerons’, and increased elevator travel limits on the nose controls. It also carried the four guns and was used in gunnery tests.
The third aircraft was lost during an flypast an a Wright Field air show and bond rally on 27 May 1945 in front of a crowd of 100,000. The aircraft, with Captain William C. Glasgow at the controls, led a formation of six aircraft across the field. Glasgow completed one roll, but during a second roll the aircraft dived into the ground. Glasgow was thrown clear, but died of his injuries, and a passing motorist was killed by fragments from the aircraft.
The P-55 had quite a few problems. The engine could overheat. It stalled in an unusual way that was rather difficult to cope with. Its controls were too sensitive at low speeds, although it performed acceptably at higher speeds. Its performance was no better than the conventional fighters of 1944, so further development was abandoned.
At one point a jet powered version of the aircraft was considered, the Model CW-24C. However the overall problems with design meant that this project was soon abandoned.
Engine: Allison V-1710-95 (F23R)
Span: 44ft 0.5in (40ft 7in for first and second prototypes)
Length: 29ft 7in
Height: 10ft 0.75in (11ft 7in in part work)
Empty weight: 6,354lb
Normal loaded weight: 7,330lb
Maximum take-off weight:
Max speed: 390mph at 19,300ft
Climb Rate: 7.1 mins to 20,000ft
Service ceiling: 34,600ft
Range: 635 miles at 296mph
Armament: Four nose mounted 0.5in machine guns