Autogiro, << `aw` tuh JY roh, >> is a type of heavier-than-air craft that is supported in the air by a rotor instead of by fixed wings, as an airplane is. Most autogiros have short, stubby wings for balance. An autogiro’s rotor spins by itself as it passes through the air. The craft differs from a helicopter, whose rotor is always powered by an engine. The chief purpose of an autogiro’s engine is to provide thrust to pull the vehicle through the air.
The rotor is set in motion through the use of gears and a clutch connected to the engine. These gears are disconnected in flight, but the rotor blades continue to revolve. A hinge at each blade’s hub makes the rotor somewhat flexible. When the airflow strikes each rotating blade, lift (upward pull) occurs. In addition, autogiros are designed in such a way that when airflow strikes the blades, it also causes them to be pulled forward around their hubs. This forward pull causes the blades to autorotate (rotate by themselves) and hold the craft aloft.
An autogiro can fly from 20 to 140 miles (32 to 225 kilometers) per hour. It cannot hover (stay motionless in the air) like a helicopter. But an autogiro requires an extremely short take-off run and can descend almost vertically to land in a small space.
Juan de la Cierva, a Spanish inventor, flew the first successful autogiro in 1923. Autogiros were later produced in Europe, the United States, and Japan. They were eventually replaced by helicopters, which are quicker and more maneuverable.
