Grumman XP-50: American Prototype Fighter

Grumman XP-50.

The Grumman XP-50 was a land-based development of the shipboard XF5F-1 Skyrocket fighter, entered into a United States Army Air Corps (USAAC) contest for a twin-engine heavy interceptor aircraft. The USAAC placed an order for a prototype on 25 November 1939, designating it XP-50, but it lost the competition to the Lockheed XP-49.

Design and Development

First assigned Design 34, later G-41 by the builder, Grumman, the design was entered into competition alongside proposals from Bell, Brewster, Curtiss, Lockheed, and Vought. The XP-50 design was similar to that of the XF5F-1 with modifications to the fuselage nose to house the nose-wheel of the tricycle landing gear and provisions for self-sealing fuel tanks and pilot armor. The planned armament was two 20 mm (.79 in) cannon and two .50 in (12.7 mm) machine guns.

Testing

During testing, the XP-50 prototype (39-2517) was lost on 14 May 1941, falling victim to a turbo-supercharger explosion that destroyed the aircraft. The test pilot Robert Hall bailed out while the XP-50 plunged into Smithtown Bay in Long Island Sound.

Based upon experience with the XF5F-1 and the XP-50, Grumman had begun work on a more advanced fighter, designated model G-51. Thus, the USAAC decided to replace the XP-50 with the newer design and recommended procurement of two G-51s, designated XP-65, using the original XP-50 expenditure order to cover the development. Consideration was given to combining the Air Corps and Navy requirements into a common design, but the weight and performance penalties inherent in conflicting requirements were considered great enough that separate designs would be needed. Since the U.S. Navy considered Grumman one of its major production sources and that producing two different model aircraft by Grumman would impede manufacture of aircraft types the U.S. Navy needed, it was decided that development of the XF7F-1 would continue, and the XP-65 as a parallel development was abandoned.

Variants

XP-50: Version of the XF5F for the United States Army Air Corps with two 1,200 hp (895 kW) Wright R-1820-67/69 engines, one built.

Crew: One

Length: 31 ft 11 in (9.73 m)

Wingspan: 42 ft 0 in (12.80 m)

Height: 12 ft 0 in (3.66 m)

Wing area: 304 sq ft (28.24 m2)

Empty weight: 8,310 lb (3,770 kg)

Gross weight: 10,500 lb (5,250 kg)

Maximum takeoff weight: 13,060 lb (6,530 kg)

Powerplant: 2 × Wright R-1820-67/69 9-cylinder air-cooled radial engines, 1,200 hp (895 kW) each

Maximum speed: 424 mph (680 km/h, 368 kn) at 25,000 ft (7,620 m)

Range: 1,250 mi (2,010 km, 1,090 nmi)

Service ceiling: 40,000 ft (12,190 m)

Rate of climb: 5,000 ft/min (25 m/s)

Armament:

2 × 20 mm (.79 in) cannons (60 rounds per gun)

2 × 0.50 in (12.7 mm) machine guns (500 rounds per gun)

2 × 100 lb (50 kg) bombs

XP-65: Improved version of the XP-50 with two R-2600-10 engines; none built—project only.

Bibliography

Dorr, Robert F. and David Donald. Fighters of the United States Air Force. London: Temple, 1990.

Green, William. War Planes of the Second World War, Volume Four: Fighters. London: MacDonald & Co. (Publishers) Ltd., 1961 (Sixth impression 1969).

Lucabaugh, David and Bob Martin. Grumman XF5F-1 & XP-50 Skyrocket, Naval Fighters Number Thirty-one. Simi Valley, California: Ginter Books, 1995.

Grumman XP-50.

Grumman XP-50.

Grumman XP-50.

Grumman XP-50.

Grumman XP-50.

Grumman XP-50.

Grumman XP-50.

Grumman XP-50.

Grumman XP-50 under construction.

Grumman XP-50 engine test.

Grumman XP-50 under construction.

Grumman XP-50.

Grumman XP-50.

Grumman XP-50 wind tunnel test model.

Grumman XP-50 wind tunnel test model.

Grumman XP-50 wind tunnel test model.

Grumman XP-50 wind tunnel test model.

Grumman XP-50 full-size mockup.

Grumman XP-50 full-size mockup cockpit view.

Grumman XP-50 full-size mockup.

Grumman XP-50.

Grumman XP-50.

Grumman XP-50.

Grumman XF5F Skyrocket: American Prototype Fighter

Grumman XF5F-1 Skyrocket experimental fighter (BuNo 1441) in flight.

The Grumman XF5F Skyrocket was a prototype twin-engined shipboard fighter interceptor. The United States Navy ordered one prototype, model number G-34, from Grumman Aircraft Engineering Corporation on 30 June 1938; its designation was XF5F-1. The aircraft had a unique appearance: The forward "nose" of the fuselage did not extend forward of the wing. Provisions were included for two 20 mm (0.787 in) Madsen cannon as armament.

Design and Development

In 1938 Grumman presented a proposal to the U. S. Navy for a twin engine carrier based aircraft, unlike any other fighter aircraft that had ever been considered. The design was for a lightweight fighter (under 10,000 lbs maximum takeoff weight) powered by two 1,200 hp Wright R-1820 engines, with propellers geared to rotate in opposite directions to cancel out the effects of each engine's torque, promising high speed and an outstanding rate of climb.

The XF5F Skyrocket was a low-wing monoplane with a short fuselage that began aft of the wing's leading edge with a twin tail assembly that featured a pronounced dihedral to the horizontal stabilizer. The main landing gear and tail wheel were fully retractable.

Operational History

The aircraft flew for the first time on 1 April 1940. Engine cooling problems arose in the initial flights, resulting in modification to the oil cooling ducts. Further modifications were made to the prototype including reduction in the height of the cockpit canopy, revising the armament installation to four 0.5 in (12.7 mm) machine guns in place of the cannon, redesign of the engine nacelles, adding spinners to the propellers, and extending the fuselage forward of the wing. These changes were completed on 15 July 1941.

Testing by Grumman test pilot "Connie" Converse indicated "the flying qualities for the XF5F-1 were good overall. The counter-rotating props were a nice feature, virtually eliminating the torque effect on takeoff ... single-engine performance was good, rudder forces tended to be high in single engine configuration. Spin recovery was positive but elevator forces required for recovery were unusually high. All acrobatics were easily performed, and of course forward visibility was excellent."

In 1941, Navy pilots tested the XF5F-1 in a fly-off against the Supermarine Spitfire, Hawker Hurricane, Curtiss P-40 Warhawk, Bell P-39 Airacobra, Bell XFL Airabonita, Vought XF4U Corsair, Grumman F4F Wildcat, and Brewster F2A Buffalo. LCDR Crommelin, in charge of the test, stated in a 1985 letter to George Skurla, Grumman president:

"for instance, I remember testing the XF5F against the XF4U on climb to the 10,000 foot level. I pulled away from the Corsair so fast I thought he was having engine trouble. The F5F was a carrier pilot's dream, as opposite rotating propellers eliminated all torque and you had no large engine up front to look around to see the LSO (landing signal officer) ... The analysis of all the data definitely favored the F5F, and the Spitfire came in a distant second. ... ADM Towers told me that securing spare parts ... and other particulars which compounded the difficulty of building the twin-engine fighter, had ruled out the Skyrocket and that the Bureau had settled on the Wildcat for mass production."

Additional changes were needed after further flight tests that were not completed until 15 January 1942. In the meantime, Grumman began work on a more advanced twin-engine shipboard fighter, the XF7F-1, and further testing with the XF5F-1 supported the development of the newer design. The prototype continued to be used in various tests, although plagued by various landing gear problems, until it was struck from the list of active aircraft after it made a belly landing on 11 December 1944.

Specifications

Crew: 1

Length: 28 ft 9 in (8.76 m)

Wingspan: 42 ft 0 in (12.80 m)

Height: 11 ft 4 in (3.45 m)

Wing area: 303.5 sq ft (28.2 m2)

Empty weight: 8,107 lb (3,600 kg)

Gross weight: 10,138 lb (4,600 kg)

Maximum takeoff weight: 10,900 lb (4,955 kg)

Powerplant: 2 × Wright XR-1820-40/42 Cyclone nine cylinder radial air-cooled engine, 1,200 hp (895 kW) each

Maximum speed: 383 mph (616 km/h, 333 kn) at sea level

Range: 1,200 mi (1,800 km, 1,000 nmi)

Service ceiling: 33,000 ft (11,000 m)

Rate of climb: 4,000 ft/min (20 m/s)

Wing loading: 33.4 lb/sq ft (163 kg/m2)

Power/mass: .23 hp/lb (0.38 kW/kg)

Armament:

4 × 0.5 in (12.7 mm) machine guns

2 × 165 lb (75 kg) bombs

Notable Appearances in Media

The XF5F Skyrocket was the propeller fighter aircraft flown by the fictional Blackhawks in Quality Comics monthly title Military Comics, which ran throughout World War II. The XF5F remained the Blackhawk Squadron's mount until their conversion to jet aircraft in Quality's retitled Modern Comics at the start of the jet age.

Bibliography

Green, William. War Planes of the Second World War, Volume Four: Fighters. London: Macdonald & Co.(Publishers), 1961.

Green, William and Gordon Swanborough. WW2 Aircraft Fact Files: US Navy and Marine Corps Fighters. London, UK: Macdonald and Jane's, 1976.

Greenberger, Robert. "Blackhawk". In Dougall, Alastair. The DC Comics Encyclopedia. London: Dorling Kindersley, 2008.

Lucabaugh, David and Bob Martin. Grumman XF5F-1 & XP-50 Skyrocket, Naval fighters number thirty-one. Simi Valley, California: Ginter Books, 1995.

Morgan, Eric B. "Grumman F7F Tigercat F.7/30". Twentyfirst Profile, Volume 1, No. 11. New Milton, Hants, UK: 21st Profile Ltd.

Morgan, Eric B. "The Grumman Twins". Twentyfirst Profile, Volume 2, No. 15. New Milton, Hants, UK: 21st Profile Ltd.

 

Grumman XF5F-1 Skyrocket (1442).

Grumman XF5F-1 Skyrocket during flight testing, circa 1938.

Grumman XF5F-1 (1442).

Grumman XF5F-1 (1442).

Grumman XF5F-1 (1442).

Grumman XF5F-1 (1442).

Grumman XF5F-1 (1442).

Grumman XF5F-1 (1442).

Grumman XF5F-1 (1442).

Grumman XF5F-1 prototype, 1941.

Grumman XF5F-1 (1442).

Grumman XF5F-1 Skyrocket.

Grumman XF5F-1 (1442).

Grumman XF5F-1 Skyrocket cockpit. Cockpit design was conventional. Visible at the bottom of the photograph is the transparency through the lower fuselage, a common feature on naval aircraft which allowed the pilot to view the carrier deck on landing approach.

Grumman XF5F-1 Skyrocket. Port side of the cockpit interior showing the twin throttle arrangement.