The Ranger V-770 is an American air-cooled inverted V-12 aero-engine developed by the Ranger Aircraft Engine Division of the Fairchild Engine & Aircraft Corporation in the early 1930s.
In 1931, the V-770 design was put to paper, based on the Ranger 6-440 series of inverted inline air-cooled engines, and test flown in the Vought XSO2U-1 Scout. In 1938 it was tested in the Curtiss SO3C Seamew and found to be unreliable with a tendency to overheat in low-speed flight. By 1941 a more developed V-770 was installed in the production Fairchild AT-21 Gunner gunnery school aircraft.
Produced from 1941 to 1945, the V-770 featured a two-piece aluminum alloy crankcase, steel barreled cylinders with integral aluminum alloy fins and aluminum alloy heads. The V-770 was the only American inverted V12-type inline air-cooled engine to reach production. The engine was used in very few Army Air Forces aircraft, among them the short lived Fairchild AT-21 twin-engine bomber trainer, and in the two Bell XP-77 light-weight fighter prototypes.