Cierva C.9

The Cierva C.9, also known as the Avro 576, was a British experimental autogyro designed by the Spanish engineer Juan de la Cierva, of which a single example was built by Avro in the late 1920s. It came from an Air Ministry order of January 1926 for two autogyros not based on the Avro 504, placed after successful demonstrations of the Spanish-built Cierva C.6B. The result was a plywood-skinned machine built like a typical single-seat biplane without its upper wing, with the undercarriage of the Avro 504N, ailerons, and rudder and elevator controls similar to those of the Avro 558. Avro chief test pilot Bert Hinkler made its first flight in September 1927, powered by a 70 hp Armstrong Siddeley Genet engine driving a four-bladed rotor of 30 feet, which was replaced from September 1928 by a rotor of about half the diameter. The trials brought no commercial success and are seen as a step towards the larger autogyros that Avro and Cierva developed until the mid-1930s. The sole machine went to the Science Museum in London in January 1930. The second machine ordered became the Avro 581, the prototype of the Avian.