Juan de la Cierva: Difference between revisions - Wikipedia

In order to achieve this, he used the ability of a lifting rotor to [[Autorotation (helicopter)|autorotate]], whereby at a suitable pitch setting, a rotor will continue to rotate without mechanical drive, sustained by the torque equilibrium of the lift and drag forces acting on the blades. This phenomenon was already known,<ref>{{Cite web | url=http://www.centennialofflight.net/essay/Rotary/early_20th_century/HE2.htm |title = Helicopter Development in the Early Twentieth Century}}</ref> and was available as a safety feature to allow controlled descent of a helicopter in the event of engine failure. With De la Cierva's autogyro, the rotor was drawn through the air by means of a conventional [[Propeller (aircraft)|propeller]], with the result that the rotor generated sufficient lift to sustain level flight, climb and descent.

Before this could be satisfactorily achieved, De la Cierva experienced several failures primarily associated with the unbalanced rolling movement generated when attempting take-off, due to [[dissymmetry of lift]] between the advancing and retreating blades. This major difficulty was resolved by the introduction of the flapping hinge. In 1923, De la Cierva's first successful autogyro was flown at Getafe aerodrome in Spain by Lt. Gomez Spencer.<ref name ="Queensland Times"/>