|The second XP-55 prototype.|
The XP-55 Ascender (Curtiss Model 249C), was a prototype fighter aircraft built by Curtiss. Along with the XP-54 and XP-56, it resulted from Army Air Corps proposal R-40C issued on November 27, 1939 calling for unconventional aircraft designs. A highly unusual design for its time, it had a canard configuration, with a pusher prop, swept wings and two vertical tails. Because of its pusher design, it was sarcastically referred to as the "Ass-ender." Like the XP-54, the Ascender was initially designed for the Pratt & Whitney X-1800 engine and had to be redesigned when the engine project was canceled. It would also be the first Curtiss fighter to use tricycle landing gear.
On June 22 1940 the Curtiss-Wright company received an Army contract for preliminary engineering data and a powered wind tunnel model. The designation P-55 was reserved for the project. The USAAC was not completely satisfied with the results of these tests and Curtiss-Wright took it upon itself to build a flying full-scale model designated CW-24B by the company. The flying testbed was powered by a 275 hp Menasco C68-5 engine. It had a fabric-covered, welded steel tube fuselage with a wooden wing. The undercarriage was fixed.
On July 10 1942 the USAAF issued a contract for three prototypes under the designation XP-55. Serial numbers were 42-78845 and 42-78847. During this time the Pratt & Whitney X-1800 engine was experiencing serious developmental delays, and would eventually be cancelled. Curtiss decided to switch to the Allison V-1710 (F16) liquid-cooled inline engine because of its proven reliability. Armament was to be two 20 mm cannon and two 0.50 inch machine guns. During the mockup phase, it was decided to switch to the more powerful 1,275 hp Allison V-1710-95 engine. The 20 mm cannon were also replaced by 0.50 inch machine guns.
The first XP-55 (42-78845) was completed on July 13, 1943. and had the same aerodynamic configuration as the final prototype CW-24B. The aircraft made its first test flight on July 19, 1943 from the Army's Scott Field near the Curtiss-Wright plant in St Louis. The pilot was J. Harvey Gray, Curtiss's test pilot. Initial testing revealed that the takeoff run was excessively long. To solve this problem the nose elevator area was increased and the aileron up trim was interconnected with the flaps so that it operated when the flaps were lowered.
On November 15, 1943 test pilot Harvey Gray, flying the first XP-55 (S/N 42-78845) was testing the aircraft's stall performance when the XP-55 suddenly flipped over on its back and fell in an uncontrolled, inverted descent. The pilot was incapable of recovering the airplane, and it fell out of control for 16,000 feet before Gray was able to parachute to safety. The aircraft was destroyed.
The second XP-55 (S/N 42-78846) was similar to the first but with a slightly larger nose elevator, modified elevator tab systems, and a change from balance tabs to spring tabs on the ailerons. It flew for the first time on January 9 1944. All flight tests were restricted so that the stall zone was avoided.
The third XP-55 (S/N 42-78847) flew for the first time on April 25 1944. It was fitted with four machine guns, and incorporated some of the ideas learned from the loss of the first XP-55. It was found that the aircraft's stall characteristics could be greatly improved by the addition of four-foot wingtip extensions, and by increasing the limits of the nose elevator travel. Between September 16 and October 2, 1944, the second XP-55 (42-78846), which had been modified to the same standards as the third aircraft, underwent official USAAF flight trials.
The performance of the XP-55 was not very impressive and was often inferior to that of more conventional fighter aircraft already in service. In addition, by 1944 jet-powered fighter aircraft were already well along in development and there was no further development of the XP-55.
A special feature of the XP-55 was a propeller jettison lever located inside the cockpit to prevent the pilot from hitting it during bailout.
The only surviving XP-55 (42-78846) was flown to Warner Robins Field in Georgia in May, 1945. Later, it would be taken to Freeman Field before being transferred to the National Air & Space Museum at the Smithsonian Institution in Washington, D.C. For many years its fuselage was displayed at the Smithsonian's Paul Garber restoration facility in Suitland, Maryland. In December, 2001 the aircraft was transferred to the Air Zoo in Kalamazoo, Michigan for restoration by Museum staff. The aircraft was found to be in overall good condition, with much of its original paint still intact. After nearly five years of restoration the aircraft was put on display at the Air Zoo on May 26, 2006 and is on long-term loan from the Smithsonian's National Air & Space Museum.
- Crew: one pilot
- Length: 29 ft 7 in (9.0 m)
- Wingspan: 40 ft 7 in (12.4 m)
- Height: 10 ft 0 in (3.0 m)
- Empty weight: 6,354 lb (2,882 kg)
- Loaded weight: 7,710 lb (3,497 kg)
- Powerplant: 1× Allison V-1710-95 liquid-cooled V12 engine, 1,275 hp (951 kW)
- 4× .50-cal (12.7 mm) machine guns
- William Green (1961). War Planes of the Second World War - Fighters, (Vol 4). London: MacDonald
- USAF Museum article: 
- NASM article: 
- USAF Museum - Curtiss XP-55
- The Plan Page - Curtiss XP-55 Ascender
- a personal page - XP-55 Ascender
- USAAF Resource Center - Curtiss XP-55
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