The entry of the XF5F during this period of American naval aviation history was of particular note as it was a twin-engined performer during a time when the first monoplanes in USN service were just beginning to take hold in inventory. Twin engines offered better range and power at the expense of complexity, maintenance requirements, and overall size on space-strapped carriers. Regardless, any advantage that could be gained against an enemy fighter was certainly entertained and Grumman had already established itself as the premiere aircraft supplier to the USN so the partnership between the two was not unwarranted.
First flight of the XF5F prototype occurred on April 1st, 1940 and this early period of testing revealed issues that forced revisions including a lengthening of both nose and engine nacelles and a reworking of the engine cooling system. Aerodynamics were further addressed by spinners added to each propeller unit and the cockpit canopy being lowered. The armament fit was changed from 2 x cannons to 2 x 0.50 caliber heavy machine guns with 2 x 0.30 caliber medium machine guns. This combination armament approach was common to many interwar American fighter planes - particularly before it was realized that a full battery of 0.50 machine guns offered the best firepower against more modern enemy fighters. On the whole, the fighter proved to have exceptional straight line speed for its time, good maneuverability, and a stellar rate-of-climb.
When tested against its contemporaries, the Grumman aircraft outshined the competition - including such war-winning classics like the British Supermarine "Spitfire" and the in-development Vought XF4U (to become the F4U "Corsair"). Due to logistical matters, however, the complex twin-engine aircraft was not pursued by the USN -instead it favored more conventional, easier-to-produce and maintain monoplanes like Grumman's other product - the F4F "Wildcat" and its successor, the F6F "Hellcat".
As such, the XF5F fell to aviation history. It was resurrected for a short time as the land-based "XP-50" (detailed elsewhere on this site) but this entry accomplished little more than its Navy sister - managing just one flying prototype herself. Both initiatives were ultimately cancelled but Grumman used these experiences to develop a fine "twin" in the late-war F7F "Tigercat" which saw production reach 364 units. These managed a combat career with the USN and USMC air services as a heavy fighter / night fighter over Korea during the Korean War (1950-1953).
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