A flettner airplane is a type of rotor airplane which uses a Flettner rotor to provide lift. The rotor comprises a spinning cylinder with circular end plates and, in an aircraft, spins about a spanwise horizontal axis. When the aircraft moves forward the Magnus effect creates lift.
Anton Flettner, after whom the rotor is named, used it successfully as the sails of a ship. He also suggested its use as a wing for a rotor airplane.
An inherent safety concern is that if power to the rotating drums was lost--even if thrust was maintained--the aircraft would lose its ability to generate lift as the drum slowed down and it would not be able to sustain flight.