Incident Cierva W.9 PX203,
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ASN Wikibase Occurrence # 311554
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Date:Tuesday 20 January 1948
Type:Cierva W.9
Owner/operator:C(A) MoS/G & J Weir Ltd (Cierva Autogiro Company)
Registration: PX203
MSN: W.9/01
Fatalities:Fatalities: 0 / Occupants: 1
Aircraft damage: Destroyed
Location:RAF Eastleigh, Hampshire -   United Kingdom
Phase: Take off
Departure airport:RAF Eastleigh, Hampshire
Destination airport:
Cierva W.9 PX203: Only one was built, and it was written off (damaged beyond repair) in a take-off accident at Eastleigh, Hampshire on 20 January 1948.

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 tail boom and exhausted to port. 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. 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 at Southampton on 22 June 1946. It was displayed at the Seventh SBAC Airshow at Radlett in 1946

The helicopter was destroyed in an accident in 1948 and the project was abandoned. The details of the accident are as follows: After early development, the C(A) MoS (Controller (Aircraft) Ministry of Supply) requested that the aircraft be fitted with dual controls. This was done, and on 20 January 1948, a test flight was attempted. However, the pilot became confused with regard to the controls as he was flying the aircraft from the starboard seat for the first time. (All previous flights had been from the sole seat, located on the port side of the aircraft).

Due to the pilot becoming confused with operating the controls, the aircraft crashed shortly after take-off at a low altitude, and rolled inverted. The pilot seems to have survived with only minor injuries

Parts of the W.9 rotor hub were used in the W.14 Skeeter prototype.


1. Halley, James (1999). Broken Wings – Post-War Royal Air Force Accidents. Tunbridge Wells: Air-Britain (Historians) Ltd. ISBN 0-85130-290-4.
2. Final Landings: A Summary of RAF Aircraft and Combat Losses 1946 to 1949 by Colin Cummings p.366


Cierva W.9

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