What happened
On 4 May 2003, a Robinson R22 Beta, registration G-WRLY, was undergoing engine start-up and run-up checks at Cranfield Airport. The aircraft, operated by Patriot Aviation, was being prepared for flight by a student pilot. During the procedure to verify the low RPM horn and caution light, the pilot attempted to reduce engine RPM while managing the collective lever.
As the pilot attempted to repeat the RPM check, the aircraft began to rotate on the ground. The pilot noted an anticlockwise rotation, while an external witness observed the helicopter spinning clockwise. During this period, the aircraft became light on its skids and lifted into a brief hover. The aircraft exhibited unstable pitching and rolling motions before descending and rolling onto its right side on the apron. The impact caused substantial damage to the engine, fuselage, transmission, and main rotor system. The pilot sustained minor injuries, and although fuel was observed spilling from the aircraft, no fire occurred.
The investigation
The investigation focused on the pilot's control inputs and the configuration of the aircraft's flight controls during the check. It was established that the pilot was performing the low RPM check with both the cyclic and collective frictions engaged and the governor turned off. This configuration was part of the operator's specific procedure at the time.
Investigators examined the torque generation and the effect of the wind. While a left-hand wind was present, it was insufficient to counteract the torque-induced yaw. The investigation also looked at the pilot's ability to react to the aircraft's movement, noting that the applied frictions significantly hindered the pilot's ability to make the necessary fine control inputs to stabilize the aircraft once it began to lift.