March 2017

2017 March

Cierva C.6C Autogyro
First flight: March 1924

The Cierva C.6C Autogiro was constructed in England under license from Juan de la Cierva for the Air Ministry by A.V. Roe. & Co. Ltd. Ordered in January 1926 under contract no. 680624/26, the Autogiro was built at Hamble (near Southampton) with official test flying commencing on June 19 with pilot Frank Courtney. The British-built Cierva C.6C was similar to the previously-built Spanish C.6 series (which first flew in early 1924) but utilized a more-powerful Clerget engine. The single-seat machine was denoted the Avro Type 574 and given the military serial number J8068.

The C.6C had a 36.1 ft (11 m) diameter cable-braced four-blade constant-chord rotor above a 34.3 ft (10.5 m) fuselage and the aircraft weighed 1,490 lb (674 kg) empty. It retained ailerons on outriggers from the earliest Cierva designs with standard Avro 504 landing gear.

After the aircraft was successfully demonstrated before George V, Queen Mary, the King and Queen of Spain, and assembled notables at the Seventh RAF Display at Hamble on July 3, 1926, it was damaged later in the year. During its repair the C.6C was fitted with stub wings incorporating ailerons which served to unload the rotor in forward flight, along with a much-wider landing gear and a more rigid attachment for the rotor blades to the rotor hub. While testing the redesigned aircraft at Hamble on February 7, 1927, a rotor blade broke off while the Autogiro was approximately 60 ft (18 m) in the air. The pilot, Frank Courtney was fortunate to survive the crash that destroyed the aircraft. Analysis of the accident, which determined that the rigidity of the blades in the plane of rotation resulted in stress on the blade roots which fatigued one blade, and a second which was found to have detached just before contact with the ground — a problem solved by addition of lead-lag ‘drag’ hinges at the blade root.

Note: The photo is of the C.6C which first flew in 1926 (note the RAF markings), while the milestone of the first flight on the calendar is for the C.6 series which commenced in 1924 in Spain.

Description: Bruce Charnov, Ph.D., J.D., FRAeS
Photo credits: Bruce Charnov and German Federal Archives

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2017 History Calendar Index