The Cierva C.30 was a Spanish autogyro designed by Juan de la Cierva and built under licence from the Cierva Autogiro Company by A V Roe & Co Ltd (Avro), Lioré-et-Olivier and Focke-Wulf.

The Cierva Autogiro Company was a British firm established in 1926 to develop the autogyro. The company was set up to further the designs of Juan de la Cierva, a Spanish engineer and pilot, with the financial backing of James George Weir, a Scottish industrialist and aviator.

Juan de la Cierva’s first British-built autogyro was the C.8 design. It and some other designs were built in conjunction with Avro. The pre-war Cierva C.30 proved popular. Nearly 150 were built under licence in the United Kingdom by Avro, in Germany by Focke-Wulf, and in France by Lioré-et-Olivier.

On 9 December 1936, Cierva was killed in the Croydon KLM airliner accident when the aircraft in which he was a passenger crashed after taking off in fog. Dr. James Allan Jamieson Bennett was promoted to Chief Technical Officer of the company and remained in the position until leaving in 1939. In addition to making important contributions to autogyro controls while at Cierva Autogyro, Bennett carried through with Cierva’s decision to offer the Royal Navy an aircraft capable of true vertical flight.

Bennett’s innovative design, a new type of rotorcraft that combined key features of the autogyro and helicopter, was tendered to the Air Ministry (Specification S.22/38) as the Cierva C.41 Gyrodyne, but preliminary work was abandoned with the outbreak of World War II. Bennett joined Fairey Aviation in 1945, where he continued the development of the C.41 design to create the first gyrodyne, the Fairey FB-1, that first flew in 1947.

In 1943, the Aircraft Department of G & J Weir Ltd. was reconstituted as the Cierva Autogiro Company to develop helicopter designs for the Air Ministry. The post-war Cierva Air Horse was at the time (1948) the world’s largest helicopter.

The first prototype of the Air Horse crashed killing Alan Marsh, Cierva’s manager and chief test pilot John “Jeep” Cable, Ministry of Supply Chief Helicopter Test Pilot, and J. K. Unsworth the Flight Engineer. This led Weir to cease further investment in the company and its development contracts were transferred to Saunders-Roe.

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