gyrodyne

Gyrodyne is a rotorcraft concept in which a rotor provides vertical lift for takeoff and landing, while thrust for forward flight is supplied by a separate propulsion system such as a propeller or jet engines. In forward flight, the rotor may be allowed to autorotate or be decoupled from power, reducing the power required to maintain speed, while the forward propulsion system handles sustained cruise. The arrangement aims to combine the vertical capability of a helicopter with the efficiency and speed potential of fixed-wing propulsion.

Historically, the gyrodyne term was used to describe designs explored in the mid-20th century that sought to improve range and speed compared with conventional helicopters, without sacrificing VTOL capability. The most famous prototype associated with the concept was the Fairey Rotodyne, which conducted hover and transition tests in the 1950s and early 1960s. Although the Rotodyne demonstrated practical VTOL operation and relatively high cruise speeds, it did not proceed to production due to a combination of technical challenges, noise concerns, and cost, along with shifting political and economic priorities.

Variations of the gyrodyne concept have influenced rotorcraft development but did not become a standard category in modern aviation. Modern tiltrotor and compound helicopter designs pursue similar goals—VTOL capability with efficient forward flight—without typically being classified as gyrodyne. The term remains primarily of historical interest within aviation literature, describing a particular approach to integrating rotor lift with separate propulsion for forward flight.

See also: Autogyro, Helicopter, Tiltrotor, Rotodyne.