How it began
Juan de la Cierva, born in Murcia in 1895 and trained as a civil engineer, designed and built gliders and airplanes between 1912 and 1919. The crash of his trimotor plane in 1919, caused by a stall, led him to look for a more stable kind of aircraft that could keep flying at low speed and come down gently if the engine failed. In January 1923 his C.4 autogiro flew successfully at Getafe aerodrome near Madrid, with Alejandro Gómez Spencer as pilot.
Before it existed
Experimenters looking for an aircraft that could be slowed down in flight and landed vertically had built many prototypes, but they were difficult to control. Early rigid rotors tipped the machine onto its side, because the blade moving forward into the airflow produced much more lift than the blade moving backward. Ordinary fixed-wing airplanes, for their part, could stall and fall out of control when they flew too slowly.
How it works
An autogiro uses a normal propeller for forward motion and a freely rotating rotor, with no engine driving it, for lift. The passing air keeps the rotor spinning. Cierva hinged each blade at the hub so that it could flap up and down: the advancing blade rises and sheds excess lift while the retreating blade drops and gains it. An autogiro has to taxi to take off and needs forward airspeed to drive its rotor, so unlike a helicopter it cannot hover.
How it spread
In 1925 Cierva went to England, demonstrated his C.6 at Farnborough and, with backing from the Scottish industrialist James Weir, founded the Cierva Autogiro Company. In September 1928 he flew a C.8 from London to Paris, the first crossing of the English Channel by a rotary-wing aircraft. Harold F. Pitcairn became his American licensee, and Cierva-type autogiros were used widely in France, Germany, Japan and the United States before World War II.
What lasted
Cierva was killed in an airliner crash at Croydon aerodrome, near London, in December 1936, and after World War II the autogiro was superseded by the more efficient helicopter. Britannica states that his articulated rotor made autogiro flight possible for the first time and led to the later development of the helicopter. Helicopter designers who followed inherited the hinged blade that he had introduced at Getafe.
