The Grumman XP-65 was to have been the Army equivalent of the Navy's Grumman F7F Tigercat twin-engined carrier-based fighter.
You may recall the Grumman XP-50, which was the Army version of the Navy's XF5F Skyrocket experimental carrier-based twin-engined fighter. The Army had ordered a single XP-50 prototype from Grumman as insurance against the failure of the Lockheed XP-49 high-altitude interceptor. Test flights revealed that the XP-50 had a good performance, but the sole prototype was destroyed on May 14, 1941 after the pilot was forced to bale out after an inflight turbosupercharger explosion. Work on the XP-50 was abandoned shortly thereafter.
Following the loss of the sole XP-50, Grumman succeeded in interesting the Army in a different proposal, named Design 46 by the company. Design 46 called for a somewhat larger twin-engined fighter powered by a pair of supercharged 1700-hp Wright R-2600 radials. Work had actually began on Design 46 in October of 1939, nearly two years before the loss of the XP-50. This initial work led to the company's Design 49, which was an export version proposed in February 1940 and to Design 51, a naval fighter adaptation which was submitted on March 24, 1941.
The Grumman proposals attracted enough attention that both the Army and the Navy decided to pursue the development of similar Grumman-designed twin-engined fighters. They were to be essentially the same aircraft, but the Army version was to have turbosupercharged engines and the Navy version was to have mechanically- supercharged engines. Both versions were to have been armed with four 0.50-in machine guns, but the Army version was to have had an additional pair of 37-mm cannon and the Navy version was to have had a additional quartet of 20-mm cannon. In addition, the Army version was to have a pressurized cockpit.
The Army ordered two prototypes of the Grumman-designed twin-engined fighter under the designation XP-65 on June 16, 1941. The Navy ordered two prototypes under the designation XF7F-1 two weeks later. However, both services eventually concluded that a single design would not actually be able to satisfy their individual requirements, and on January 16, 1942 the Army decided to back out of the project in order to permit Grumman to optimize their design to meet naval requirements.
The XP-65 was destined to be Grumman's last fighter submission to the USAAF. Thereafter, all of Grumman's fighter designs were submitted to the Navy.
Estimated performance of the XP-65 included a top speed of 427 mph at 25,000 feet, a service ceiling of 42,000 feet, and a normal range of 825 miles. Weights were to be 15,943 pounds empty and 21,425 pounds loaded.