Similar to the C.3 and also equipped with a Le Rhone 9 JA 110hp engine, the C.5 with a three-bladed rotor first flew at Getafe in July 1923.
The C.6, unlike its predecessors financed from private sources, was built with the help of subsidies from the Spanish Government and made its maiden flight in May 1924. It had an Avro 504K fuselage with ailerons on outrigger spars, a rotary Le Rhone 9 JA 110hp engine and a four-bladed rotor with flapping hinges 10.97m in diameter and turning at 140 r.p.m.
The rotor was made to turn at up to 60 r.p.m. By this means, the autogyro's take-off was shortened by the use of a rope.
On 12th December 1924 the first successful cross-country flight was made over the 12 kilometres between the airports of Cuatro Ventros and Getafe.
In October 1925 the C.6 was brought to England and performed a series of demonstrations at the Royal Aircraft Establishment, Farnborough. These were so convincing that the Air Ministry decided to order several autogyros to be tried out by the Royal Air Force. This gave rise to the Cierva Autogyro Company Ltd, which managed the rights in La Cierva's inventions. The firm of A.V.Roe was selected to build the British C.6's.
P.Lambermont "Helicopters and Autogyros of the World", 1958