A rotor kite or gyroglider is an unpowered, rotary-wing aircraft. Like an autogyro or helicopter, it relies on lift created by one or more sets of rotors in order to fly. Unlike a helicopter, autogyros and rotor kites do not have an engine powering their rotors, but while an autogyro has an engine providing forward thrust that keeps the rotor turning, a rotor kite has no engine at all, and relies on either being carried aloft and dropped from another aircraft, or by being towed into the air behind a car or boat. As of 2009, no country in the world requires a license to pilot such a craft.
Research into rotor kites began in earnest during World War II, and one type in particular, the Focke Achgelis Fa 330, reached active service, being towed behind German U-boats as an aerial observation platform. In the United Kingdom, Raoul Hafner designed the Rotachute as a means of deploying paratroops, and a larger version, the Rotabuggy, was trialled as a means of air-dropping a jeep, but neither of these aircraft progressed past the experimental stage. Plans to similarly equip a tank never left the drawing board.
During the 1950s, rotor kites were developed as recreational aircraft, largely due to the efforts of Dr. Igor Bensen in the United States, whose Bensen Aircraft Corporation produced a series of such aircraft, dubbed "gyrogliders" by Bensen. These were marketed as plans or kits for building at home, beginning with the B-5 and culminating with the B-8 by the end of the decade. The Bensen designs became so ubiquitous that the term "gyroglider" is sometimes used to refer to any rotor kite, regardless of manufacturer. In the 1960s, a B-8 gyroglider was evaluated by the United States Air Force as a "Discretionary Descent Vehicle", to provide a more controllable alternative than a parachute for a pilot ejecting from a stricken aircraft.
Note 1: A tiltwing or tiltrotor aircraft functions as an aeroplane during normal (horizontal) flight and as a helicopter during low-speed flight.
Note 2: For full-size aircraft with powered rotors the rotor is normally tilted to achieve thrust (e.g. in a helicopter). Some toys (e.g. balloon helicopter) do have a powered rotor with no means to tilt the rotor to produce horizontal thrust.