Gyrodyne

A gyrodyne is a type of VTOL heavier-than-air aircraft that uses a helicopter rotor system (either in unicopter, bicopter or multicopter forms) driven by its own engines only for takeoff, landing and hovering, and one or more conventional propellers or jet engines to provide thrust during forward flight. During cruising flight, the rotor(s) are left in unpowered autorotation like an autogyro (but unlike a compound helicopter, whose main rotor remains powered), and lift is provided by a combination of the airfoils on both the rotor(s) and fixed wings. The gyrodyne is one of a number of similar concepts (such as convertiplanes like tiltrotors and tiltwings) which attempt to combine the low-speed maneuverability of rotorcraft with the high airspeeds of conventional airplanes. The gyrodyne was invented by British engineer Dr. James Allan Jamieson Bennett, the chief technical officer of Cierva Autogiro, as an alternative to the helicopter, in response to an Air Ministry specification. The gyrodyne was envisioned as an intermediate type of rotorcraft between a helicopter and an autogyro, its rotor operating parallel to the flightpath to minimize axial flow with one or more propellers providing propulsion. Bennett's patent covered a variety of designs, which has led to some of the terminological confusion – other issues including the trademarked Gyrodyne Company of America and the Federal Aviation Administration (FAA) classification of rotorcraft. In recent years, a related concept has been promoted under the name heliplane. Originally used to market gyroplanes built by two different companies, the term has been adopted to describe a Defense Advanced Research Projects Agency (DARPA) program to develop advances in rotorcraft technology with the goal of overcoming the current limitations of helicopters in both speed and payload.