The Lycoming XR-7755-3 is the largest, most powerful reciprocating aircraft engine in the world. During World War II, the U.S. Army Air Forces requested an engine with high takeoff power and low fuel consumption for a yet-to-be designed long-range bomber and transport. Lycoming began designing the engine in early 1944, and it was ready for testing by mid-1946. It featured nine dual-lobe overhead camshafts, which shifted axially for takeoff and cruising efficiency, and a two-speed, geared, dual-rotation propeller drive. Lycoming built two XR-7755-3 prototypes. The company and the Army successfully tested them, but neither engine ever flew in an airframe. The proven reliability of the new gas turbine engines introduced after World War II made the XR-7755-3 obsolete before it could be fully developed. The engine displayed here is the sole survivor. Transferred from the U.S. Army Air Forces, Park Ridge, III. Picture taken at the National Air and Space Museum's Steven F. Udvar-Hazy Center in Chantilly, Virginia, USA.

Type: Reciprocating, 36 cylinders, nine 4-cylinder rows, radial, liquid cooled
Power rating: 3,729 kW (5,000 hp) at 2,600 rpm
Displacement: 127 L (7,755 cu in)
Weight: 2,783 kg (6,130 lb)
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