The Cierva W.5 was a

helicopter A helicopter is a type of rotorcraft in which lift and thrust are supplied by horizontally spinning rotors. This allows the helicopter to take off and land vertically, to hover, and to fly forward, backward and laterally. These attributes ...

developed by the Cierva Autogiro Company in the

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Europe, off the north-western coast of the European mainland, continental mainland. It comprises England, Scotlan ...

. It was a single seater twin rotor helicopter- the rotors were mounted side-by-side on outriggers- with a wooden frame. It was powered by a 50 hp 4-cylinder air-cooled Weir engine. Its first flight was at Dalrymple, Ayrshire, on 7 June 1938, and it is considered to have been the world's second fully practical helicopter. Pitch and Yaw control was achieved by tilting the rotor disks, roll control by differential pitch input to the rotors. Rotor thrust was controlled directly by the motor speed, which damped the response heavily.Book: Principles of Helicopter Aerodynamics Ch 1.1 The first successes/ By J. Gordon Leishman (2edn, 2006, ) Cambridge Aerospace Series

References

Reference to the W.5 in the history of British research and developments in the Helicopter field on the website by Vic Flintham
British helicopters Aircraft first flown in 1938 Transverse rotor helicopters Single-engined piston helicopters Cierva aircraft 1930s British helicopters {{Aero-1930s-stub