The Flettner Fl 185 was an experimental German gyrodyne developed by Anton Flettner, a machine which could fly both as a helicopter and as a gyroplane.
This aircraft was developed in 1936 with support of the Kriegsmarine. It was powered by a 160 horsepower (120 kW) BMW-Bramo Sh 14 A radial piston engine with forced-air cooling, mounted at the nose. The engine drove a 12 m diameter main rotor and two auxiliary propellers mounted on outriggers attached to the fuselage.
At take-off or when hovering, the auxiliary propellers worked in opposition to each other and served to cancel the torque of the main rotor, a function handled by a single, variable-pitch tail rotor on contemporary helicopters. In forward flight, however, both propellers worked to provide forward thrust while the rotor autorotated, as in a twin-engined autogyro. The landing gear consisted of a nose-wheel, two smaller stabilising wheels under the outriggers and a tail skid. Only one prototype was constructed.
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