|National origin||United States|
|First flight||14 November 1942|
|Developed from||Lockheed P-38 Lightning|
The Lockheed XP-49 (company Model 522) was an advancement on the P-38 Lightning for a fighter in response to U.S. Army Air Corps proposal 39-775. Intended to use the new 24-cylinder Pratt & Whitney X-1800 engine, this proposal, which was for an aircraft substantially similar to the P-38, was assigned the designation XP-49, while the competing Grumman Model G-46 was awarded second place and designated XP-50.
Ordered in October 1939 and approved on January 8, 1940, the X-1800-powered XP-49 would feature a pressurized cockpit and armament of two 20 mm (.79 in) cannon and four 0.5 in (12.7 mm) machine guns. However, after two months into the contract a decision was made to substitute the Continental XI-1430-1 (or IV-1430) twelve cylinder liquid-cooled inverted vee engines for the X-1800. The XP-49, 40-3055, first flew on 11 November 1942. A crash landing on 1 January 1943  occurred when the port landing gear failed to lock down due to a combined hydraulic and electric failure, and the XP-49 flew again on 16 February 1943 after repairs were made. The preliminary flight data showed that performance of the XP-49 was not sufficiently better than the production P-38, and with a questionable future for the XI-1430 engine, to warrant disruption of the production line to introduce the new model aircraft. Consideration of quantity production was therefore abandoned.
The aircraft was flown to Wright Field, and after various problems further work on the XP-49 was halted.
Specifications (XP-49) 
- Crew: One
- Length: 40 ft 1 in (12.2 m)
- Wingspan: 52 ft (15.8 m)
- Height: 9 ft 10 in (3.0 m)
- Wing area: 327.5 ft² (30 m²)
- Empty weight: 15,410 lb (6990 kg)
- Loaded weight: 18,750 lb (8505 kg)
- Powerplant: 2 × Continental XI-1430-1 inverted V-12s, 1,600 hp (1,193 kW) each
- Maximum speed: 406 mph (653 km/h) 15,000 ft (4,570 m)
- Range: 679 mi (1,093 km)
- Rate of climb: 3,300 ft/min (16.8 m/s)
- 2 × 20 mm (.79 in) cannons
- 4 × 0.5 in (12.7 mm) machine guns
See also 
- Related development
- Related lists
- Green, William. War Planes of the Second World War, Volume Four: Fighters. London: MacDonald & Co. (Publishers) Ltd., 1961 (Sixth impression 1969). ISBN 0-356-01448-7.
- Green, William and Swanborough, Gordon. WW2 Aircraft Fact Files: US Army Air Force Fighters, Part 2. London: Macdonald and Jane's Publishers Ltd., 1978. ISBN 0-354-01072-7.
Media related to Lockheed XP-49 at Wikimedia Commons