Grumman F5F Skyrocket
The Grumman F5F Skyrocket, flown as the XF5F-1, was a twin-engined, single-seat carrier fighter prototype built for the United States Navy. Ordered as a single prototype in June 1938 and first flown on 1 April 1940, it paired two Wright Cyclone radials with a fuselage so short that the wing's leading edge stood ahead of the nose. Its climb impressed the pilots who tested it against contemporary fighters in 1941, but newer single-engined monoplanes had outclassed it before testing finished, and it never entered production. The prototype flew on as a test aircraft until December 1944, and its trials informed the F7F Tigercat.
Why It Mattered
In 1938, when the most modern fighters in United States Navy service were still biplanes, Grumman proposed something the Navy had never considered: a twin-engined, single-seat monoplane fighter meant to fly from carriers. The idea traded the usual single engine for two, promising speed and a rate of climb that contemporary fighters could not match. Only one prototype was ever ordered, and it never entered production, overtaken within two years by faster single-engined monoplanes. Its test flying still mattered: the Skyrocket's trials fed directly into the twin-engined F7F Tigercat, the Grumman design that did reach production.
Design Notes
Designated G-34 by Grumman, the aircraft was a low-wing monoplane whose short fuselage began behind the wing, so that the wing's leading edge ran ahead of the nose. Two Wright R-1820 Cyclone radials of 1,200 horsepower each sat in short nacelles at the wing's leading edge, their propellers geared to turn in opposite directions so that each engine's torque cancelled the other's. The tail carried twin fins and rudders on a horizontal stabiliser with pronounced dihedral, and the main wheels and tail wheel all retracted. As designed, the nose held provision for two Madsen cannon; during testing the fit was changed to four 0.5-inch machine guns. In its original form the fuselage stopped behind the wing; tests led Grumman to lengthen it forward of the wing, along with redesigned nacelles, propeller spinners and a lower canopy.
Operational History
The Navy ordered a single prototype on 30 June 1938, designated XF5F-1, but the aircraft took time to build and did not fly until 1 April 1940. Early flights uncovered engine cooling trouble, taken up first in changes to the oil cooling ducts, and the prototype then went through a long series of modifications that ran into January 1942. Test pilot "Connie" Converse reported the flying qualities good overall and the forward view excellent, helped by the absence of a nose ahead of the wing. In a 1941 Navy fly-off the Skyrocket was measured against eight other fighters, including the Spitfire and the prototype Corsair; the officer in charge, LCDR Crommelin, recalled decades later that he had pulled away from the Corsair in a climb to 10,000 feet so fast he thought it had engine trouble, and that the test data favoured the F5F. The Bureau nevertheless chose the single-engined Wildcat for mass production, judging the twin harder to build and support, and no production order for the Skyrocket followed. Grumman flew the prototype on in test work, where its trials supported the XF7F-1 then in development, until a belly landing in December 1944 ended its career. The Army's land-based derivative, the XP-50, flew in February 1941 but was lost that May when a turbocharger explosion forced its pilot to bail out; it too never entered production.
Afterlife
No Skyrocket survives: the only prototype built was struck from the active list after its belly landing in December 1944. The design's real legacy was the F7F Tigercat, Grumman's twin-engined carrier fighter, which reached production using experience the Skyrocket's test programme had gathered. In print, the XF5F found a second life as the mount of the fictional Blackhawk squadron in Quality Comics' Military Comics, which kept the obscure prototype in front of wartime readers long after the Navy had passed it over. Grumman itself moved on quickly: work on the Tigercat had begun while the Skyrocket was still flying its test programme.