XP-55 Ascender
Curtiss XP-55 Ascender in flight.
General information
Type	Fighter
National origin	United States
Manufacturer	Curtiss-Wright Corporation
Status	Canceled at flight-test stage
Number built	3
History
First flight	19 July 1943

The Curtiss-Wright XP-55 Ascender (company designation CW-24) is a 1940s United States prototype fighter aircraft built by Curtiss-Wright. Along with the Vultee XP-54 and Northrop XP-56, it resulted from United States Army Air Corps proposal R-40C issued on 27 November 1939 for aircraft with improved performance, armament, and pilot visibility over existing fighters; it specifically allowed for unconventional aircraft designs. An unusual design for its time, it had a canard configuration with a rear-mounted engine, and two vertical tails at end of swept wings. Because of its pusher design, it was satirically referred to as the "Ass-ender".^[1] Like the XP-54, the Ascender was designed for the 1,800 hp Pratt & Whitney X-1800 24-Cylinder H-engine, but was redesigned after that engine project was canceled. It was also the first Curtiss fighter aircraft to use tricycle landing gear.

In June 1940, the Curtiss-Wright company received an Army contract for preliminary engineering data and a powered wind tunnel model.^[2] The designation 'P-55' was reserved for the project. The exhaustive wind-tunnel tests that from November 1940 through January 1941 left the USAAC dissatisfied with the results of these tests.^[3][4]

Accordingly, Curtiss-Wright built at their St Louis division a flying full-scale mockup they designated CW-24B.^[5] The flying testbed was powered by a 275 hp (205 kW) Menasco C68-5 inline engine.^{[3][6][unreliable source?]} It had a fabric-covered, welded steel tube fuselage with a wooden wing.^[7] The undercarriage was non-retractable.^[3] The canard did not carry load but only trimmed flight.^[5] The CW-24B model completed its maiden flight in December 1941.^[3] From November 1941 to May 1942, the Model 24B logged 169 flights at Muroc Dry Lake, California. The tests appeared to show potential.^[4] The CW-24B then went to NACA at Langley Field for wind tunnel tests.^[5]

On 10 July 1942, the United States Army Air Forces issued a contract for three prototypes under the designation XP-55.^[4][6] Serial numbers 42-78845 through 42-78847 were assigned to the aircraft. During this time, the Pratt & Whitney X-1800 H-block sleeve valve engine was delayed, and was eventually canceled.^[7] Curtiss decided to switch to the 1,000 hp (750 kW) Allison V-1710^[4] (F16) liquid-cooled inline engine because of its proven reliability.^[7] Armament was to be two 20 mm (0.79 in) Hispano autocannon and two 0.50 in (12.7 mm) M2 Bowning heavy machine guns.^[3] During the mock-up phase, engineers switched to the 1,275 hp (951 kW) V-1710-95.^[4][8] The 20mm cannons were also replaced by 0.50-in machine guns.^[6]

One feature of the XP-55 was a propeller jettison lever inside the cockpit to prevent the pilot from hitting the propeller during bailout. The jettison device was invented by W. Jerome Peterson while working as a design engineer for Curtiss-Wright.^[3][7]

Three XP-55 prototypes were built. Two were destroyed during flight testing, as a result of their propensity for sudden wing stalls.

The first XP-55 (42-78845) was completed and delivered on 13 July 1943, with the same configuration as the final prototype CW-24B. The aircraft made its first flight on 19 July 1943^[3][8] from the Army's Scott Field near the Curtiss-Wright plant in St Louis, Missouri.^[7] The pilot was J. Harvey Gray,^[3] Curtiss' test pilot. Testing revealed the takeoff run was excessively long. To solve this problem, the nose elevator size was increased and the aileron up-trim was interconnected with the flaps so it operated after the flaps were lowered.^[7]

In 15 November 1943, test pilot Harvey Gray, flying the first XP-55 (S/N 42-78845), was testing the aircraft's stall performance at altitude. Suddenly, the XP-55 inverted into an uncontrolled descent. The engine failed "making recovery impossible"^[2] and it fell out of control for 16,000 ft (4,900 m) before Gray was able to parachute to safety. The aircraft was destroyed and "left a smoking hole in the ground".^[4][7]

The second XP-55 (serial 42-78846) was similar to the first, but with a slightly larger nose-elevator,^[7] modified elevator-tab systems, and a change from balance tabs to spring tabs on the ailerons. It flew for the first time on 9 January 1944.^[4][7] All flight tests were restricted so the stall-zone was avoided; included no stalling below 20,000 ft.^[5][7][9]

The third XP-55 (serial 42-78847) flew for the first time on 25 April 1944. Modifications resulting from the investigation of the crash of the first prototype were introduced during construction; the addition of four-foot wingtip extensions to improve the stall characteristics and increasing the limits of the nose elevator travel to improve recovery if a stall did occur.^[2] It was the only prototype to be fitted with armament - four 0.5-inch machine guns.^[5]

After the second XP-55 (42-78846) was given the same modifications as the third prototype, it underwent official USAAF flight trials between 16 September and 2 October 1944.

The third prototype XP-55 (s/n 42-78847) was lost on 27 May 1945, during the closing day of the Seventh War Bond Air Show at the Army Air Forces Fair at Wright Field in Dayton, Ohio.^[7][10] After a low pass in formation with a Lockheed P-38 Lightning and a North American P-51 Mustang^[7] on each wing, its pilot, William C. Glasgow, attempted a slow roll,^[7] but lost altitude and crashed, sending flaming debris into occupied civilian ground vehicles on a highway near the airfield. The crash killed Glasgow and four civilians on the ground.^[7][11]

In test flights the XP-55 achieved 390 mph at 19,300 feet but there were engine cooling problems.^[2] In terms of overall performance, testing of the XP-55 revealed it to be inferior to conventional fighter aircraft.^[4][7][12] In addition, by the end of 1944, German and British jet-powered fighters were fully operational, and the Lockheed XP-80 was about to commence operational trials with USAAF units in Italy. Development of completely new piston-engine fighter designs was regarded as redundant; further development of such aircraft was terminated, including the XP-55.

• 42-78845: crashed during vertical dive on November 15, 1943. Pilot bailed out.^[13]
• 42-78846: on display at the Air Zoo in Kalamazoo, Michigan. It is on long-term loan from the Smithsonian's National Air and Space Museum in Washington, D.C.^{[4][7][8][14]} Used for official performance tests, flying a total of 27 hours.^[8]
• 42-78847: crashed during air show at Wright Field, Ohio on May 27, 1945. Pilot killed.^[7][15]

Data from Green and Swanborough 1977^{[16] [17]} Air and Space Museum ^[18]

General characteristics

• Crew: One (pilot)
• Length: 29 ft 7 in (9.02 m)
• Wingspan: 40 ft 7 in (12.37 m)
• Height: 10 ft 0 in (3.05 m)
• Wing area: 235 sq ft (21.8 m²)
• Empty weight: 6,354 lb (2,882 kg)
• Gross weight: 7,710 lb (3,497 kg)
• Max takeoff weight: 7,930 lb (3,597 kg)
• Powerplant: 1 × Allison V-1710-95 liquid-cooled V12 engine, 1,275 hp (951 kW)

Performance

• Maximum speed: 390 mph (630 km/h, 340 kn) at 19,300 feet (5,900 m)
• Range: 635 mi (1,022 km, 552 nmi)
• Service ceiling: 34,600 ft (10,500 m)
• Wing loading: 32.8 lb/sq ft (160 kg/m²)
• Power/mass: 0.16 hp/lb

Armament

• Guns: 4 × 0.50 in (12.7 mm) machine guns in the nose

Aircraft of comparable role, configuration, and era

• Ambrosini SS.4
• Kyushu J7W Shinden
• Miles M.35 Libellula
• Northrop XP-56 Black Bullet
• SAAB 21
• Vultee XP-54
• Henschel Projekt P.75

Related lists

• List of aircraft of World War II
• List of fighter aircraft
• List of military aircraft of the United States
• Lists of air show accidents and incidents

• Balzer, Gerald H. (2008). American Secret Pusher Fighters of World War II: XP-54, XP-55, and XP-56. North Branch, MN: Specialty Press. ISBN 978-1-58007-125-3.
• Bowers, Peter M (1979). Curtiss Aircraft, 1907–1947. London: Putnam. ISBN 0-370-10029-8.
• Bowers, Peter M (1984). Unconventional Aircraft. Blue Ridge Summit, PA: Tab Books.
• Green, William (1969). War Planes of the Second World War, Volume Four: Fighters (Sixth ed.). London: MacDonald & Co. (Publishers) Ltd. ISBN 0-356-01448-7.
• Green, William; Swanborough, Gordon (1977). WW2 Aircraft Fact Files: US Army Air Force Fighters, Part 1. London: Macdonald and Jane's Publishers Ltd. ISBN 0-356-08218-0.
• Jenkins, Dennis R.; Landis, Tony R. (2008). Experimental & Prototype U.S. Air Force Jet Fighters. North Branch, MN: Specialty Press. ISBN 978-1-58007-111-6.
• McIntyre, Violet. Niagara Gazette, Niagara Falls, NY, 11 November 2004^{[full citation needed]}
• Rubenstein, Murray; Goldman, Richard M. (1974). To Join With The Eagles : Curtiss-Wright aircraft, 1903-1965. Garden City, NY: Doubleday.

• Balzer, Gerald H. (2014). Curtiss XP-55 Ascender. Air Force Legends. Vol. 217. Simi Valley, CA: Ginter Books. ISBN 978-0-9892-5833-3.

Wikimedia Commons has media related to Curtiss-Wright XP-55 Ascender.

• NMUSAF – Curtiss XP-55
• NASM article
• XP-55 Ascender by Joe Baugher
• Curtiss Wright XP-55 Ascender -USAAF Resource Center at warbirdsresourcegroup.org
• Dayton Air Show History
• "Flying Backwards to the Future", Popular Science, August 1945
• PlaneHistoria - XP-55 Ascender: the Back-to-Front Fighter
• The FlyingMag - The Short, Unconventional Life of the Curtiss XP-55 Ascender