Lockheed XP-49
The Lockheed XP-49 was a development of the P-38 Lightning 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 XP-49 was to feature a pressurized cockpit and armament of two 20 mm cannon and four .50 in machine guns. Two months into the contract, a decision was made to substitute the Continental XI-1430-1 (or IV-1430) for the X-1800. The XP-49, 40-3055, first flew on 11 November 1942. The prototype force-landed on 1 January 1943, when the port landing gear failed to lock down due to combined hydraulic and electrical system failures. The XP-49 next flew 16 February 1943, after repairs were made. Preliminary flight data showed performance was not sufficiently better than the production P-38, especially given the questionable future of the XI-1430 engine, to warrant disruption of the production line to introduce the new model aircraft. Consideration of quantity production was therefore abandoned.