What happened
On 18 July 2007, a Robinson R22 Beta, registration G-OBIL, was undergoing engine start-up procedures at Peterborough (Conington) Airfield in Cambridgeshire. The aircraft was positioned on a dry concrete apron facing south, with winds recorded at 210 degrees at 12 knots. The pilot, a student, had successfully completed initial interior and engine start-up checks, including engaging the rotor rpm governor while the engine was below 80% rpm.
As the pilot increased the rotor rpm toward the target of 104%, the aircraft began to rotate anti-clockwise across the apron. The pilot reacted by immediately closing the throttle; while the rpm initially decreased, the governor subsequently reopened the throttle to restore the rpm to 104%. During this period, the aircraft continued to spin for approximately six revolutions. The rotation ended when the tail rotor struck the grass, resulting in severe damage to the tail rotor and main frame distortion. There were no injuries to the pilot, and the aircraft was shut down and vacated normally.
The investigation
Investigators examined the actions of the pilot and the mechanical operation of the rotor rpm governor. The investigation established that the pilot had inadvertently applied left rudder pedal while increasing the throttle. This action introduced an anti-clockwise turning force to the aircraft. The pilot noted that during the rotation, his primary focus was on maintaining the aircraft's upright position and managing the throttle, which led him to neglect applying the necessary corrective pedal input.
Findings
- The pilot applied left rudder pedal during the increase of rotor rpm.
- The application of left pedal created an anti-clockwise turning force that initiated the ground rotation.
- The pilot's concentration on maintaining aircraft stability and throttle control prevented the application of corrective pedal input.