| W.9 | |
|---|---|
 | |
| Role | Experimental helicopter |
| Manufacturer | Cierva Autogiro Company, Ltd. |
| First flight | 1945 |
| Retired | 1946 |
| Primary user | Air Ministry |
The Cierva W.9 was a British 1940s experimental helicopter with a three-blade tilting-hub controlled main rotor, and torque compensation achieved using a jet of air discharged from the rear port side of the fuselage.
In 1943, primary investor G & J Weir Ltd. revived the moribund Cierva Autogiro Company to develop an experimental helicopter to Air Ministry Specification E.16/43. The W.9 was to investigate James G. Weir's contention that a powered tilting hub-controlled rotor with automatic collective pitch control, and torque reaction control using jet efflux, was both safer and more efficient than the Sikorsky R-4 helicopter fitted with manually controlled main rotor cyclic and collective pitch and the anti-torque tail rotor system. The W.9 was completed late in 1944 and assigned serial PX203. It was damaged during ground-running due to incorrect control phasing arising from a high order of pitch-flap coupling, and did not start test flying until 1945.
The most visible characteristic of the W.9 was torque compensation and directional control by using blown air rather than a tail rotor. A variable pitch fan cooled the engine; the heated air and engine exhaust passed through the long hollow tailboom and exhausted to port. [1] Foot pedals controlled the fan pitch. Of more importance, however, was the shaft-driven hydraulically-actuated rotor hub with rotational speed variation to give automatic collective pitch control. [2] Development of the rotor system resulted in a tilting hub combined with cyclic pitch control of each blade to minimize control forces. Manual control of collective pitch was added to the automatic collective pitch change system to provide precise vertical control in hover and the ability to cushion a landing from an autorotative descent.
The W.9 was first publicly demonstrated during an air display in Southampton on 22 June 1946. [3] It was displayed at the Seventh SBAC Airshow at Radlett in 1946 [4]
The helicopter was destroyed in an accident in 1946 and the project was abandoned. Parts of the W.9 rotor hub were used in the W.14 Skeeter prototype.
Data from Flight [5]
General characteristics
United Kingdom 
Juan de la Cierva y Codorníu, 1st Count of la Cierva was a Spanish civil engineer, pilot and aeronautical engineer. His most famous accomplishment was the invention in 1920 of a rotorcraft called Autogiro, a single-rotor type of aircraft that came to be called autogyro in the English language. In 1923, after four years of experimentation, De la Cierva developed the articulated rotor, which resulted in the world's first successful flight of a stable rotary-wing aircraft, with his C.4 prototype.
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The Illustrated Encyclopedia of Aircraft (Part Work 1982-1985). Orbis Publishing.