German engineer Felix Wankel conceived his rotary engine in 1924 and patented it in 1936. It featured a triangular cam connected to the drive shaft that acted like the pistons in a four-stroke cycle engine. Wankel submitted his designs to the German automobile company NSU. Wankel and NSU built and tested the first rotary in early 1957. The engine saw its greatest success in Mazda automobiles, but has also been used in motorcycles, go-karts, air-conditioner systems, and aircraft.
Wright Aeronautical adapted three RC2-60 automobile engines for flight testing in 1970. The one displayed here was probably the first Wankel engine to power an airplane, a Cessna Cardinal. Another powered a Lockheed Q-Star to demonstrate feasibility, performance, and quiet flight. The third powered a Hughes TH-55 helicopter.
Economic considerations (e.g. fuel burn, emissions) seem to have greatly diminished interest in the Wankel concept more recently.