Answer: autogyros

AnswerCrossword Clue
AUTOGYROSSome aircraft with propellers
autogyrosAUTOGYRO, a type of aircraft, also AUTOGIRO
autogyrosA form of aircraft with freely rotating horizontal vanes and a propeller. It differs from a helicopter in that the vanes are not powered but rotate in the slipstream, propulsion being by a conventional mounted engine