What happened
On 28 March 2002, a Robinson R44, registration G-LNDS, was being prepared for a private flight at Wellesbourne-Mountford Airport. The aircraft was parked on a concrete pad facing west. During the pre-flight inspection sequence, the pilot raised the collective lever to verify the functionality of the low rotor RPM warning lights and horns, a standard procedure performed before increasing the rotor RPM to 102%.
As the collective was raised, the helicopter began a slow rotation to the left. This yawing motion continued for approximately three full turns. During this movement, the rear portion of the left skid caught in the grass adjacent to the concrete pad. This contact caused the aircraft to pitch backward, resulting in the tail striking the ground. The impact caused extensive damage to the tail rotor before the helicopter settled back into an upright position on the pad. There were no injuries to the two crew members on board.
The investigation
Investigators examined the aircraft's control systems to determine if any mechanical failures contributed to the uncommanded yaw. Maintenance personnel inspected the helicopter and found no pre-existing defects in the controls that would have caused the movement. An observer present at the scene, who was taking photographs nearby, noted that the movement of the aircraft was consistent with the application of full left yaw pedal input.