The Grumman XP-65 was a twin engine fighter that was developed alongside the Navy’s F8F Tigercat, but that was cancelled early in 1942 before reaching the prototype stage.
Grumman had been working on twin engine fighters since the late 1930s. On 30 June 1938 the US Navy placed an order for a prototype of the Grumman XF5F-1 Skyrocket (Grumman G-34), a radical design with a very short fuselage that ended before the leading edge of the centre section of the wing. This was followed on 25 November 1939 by a USAAC order for a single prototype of the closely related Grumman XP-50 Skyrocket (Grumman G-46). This had a longer nose, giving it a more conventional appearance, but was otherwise similar.
The XF5F-1 made its maiden flight on 1 April 1940. The prototype suffered from a series of problems – the engine overheated, controls were problematic and there were problems with the landing gear. Although it lived up to the performance promises of 1938, they were no longer so impressive by 1940. The sole XF5F-1 continued to be developed until it was lost in 1944, but wasn’t considered for production.
The XP-50 made its maiden flight early in 1941. It appears to have performed well in its early trials, but was lost on 14 May 1941 after a turbo-supercharger explosion forced the test pilot to bail out. The loss of the only XP-50 meant that the project was abandoned.
Another reason for the loss of interest in the XP-50 was that Grumman were already working on a more advanced design, using significantly more powerful engines, the Grumman G-51. This was another twin engine aircraft, this time powered by the Pratt & Whitney R-2800 Double Wasp air cooled eighteen cylinder radial engine. It was to have thick mid mounted wings with a straight leading edge, tapered trailing edge and significant dihedral. The engines were to be carried in nacelles partly under the wings. The fuselage was to be narrow but tall with a oval cross section, with the cockpit just in front of the leading edge of the wing. It was to use tricycle landing gear.
Initially the hope was that the basic G-51 design could be used by the USAAC and the US Navy. The most obvious difference between the two versions was that the Army version would use turbo-superchargers. The Navy version would remove the superchargers, but would need arrestor hooks, folding wings.
Both services were interested in the design. The USAAC moved first, placing an order for a prototype on 19 May 1941. The Navy wasn’t far behind, ordering a prototype of the XF7F-1 on 30 June 1941. Both versions had the Grumman designation G-51.
Work on the two designs hadn’t made much progress when the Japanese attacked Pearl Harbor. In the aftermath of the attack every development project was examined. By this point it was already clear that the Army and Navy didn’t agree on what was needed on the G-51. As Grumman was already an established supplier of Naval fighters the XP-65 was cancelled on 16 January 1942.
It is sometimes claimed that the Army made their decision after testing a XF7F. However the first unofficial flight of the XF7F prototype didn’t take place until 2 November 1943 and the first official flight on 3 November, nearly two years after the XP-65 had been cancelled.
All stats proposed or estimated
Engine: Two Pratt & Whitney R-2800-22W Double Wasp air cooled 18-cylinder radial engines
Power: 1,700hp each
Span: 52ft 6in
Length: 46ft 5in
Height: 15ft 2in
Empty weight: 15,943lb
Maximum take-off weight: 21,425lb
Max speed: 429mph at 19,200ft
Climb Rate: 4,530ft/ min
Service ceiling: 40,700ft
Endurance: 825 miles
Armament: Four 20mm cannon and four 0.5in machine guns