What happened
On 22 April 2006, a Replica SE5A, registration G-BMDB, was involved in a ground accident at Boscombe Down Airfield in Wiltshire. The aircraft, which was being operated on a private flight, was parked on the grass adjacent to Runway 23. After starting the engine and setting the RPM to a slow idle, the pilot moved the wheel chocks to a different location to comply with airfield regulations that prohibit leaving chocks on the grass.
While the pilot was away from the cockpit, the aircraft began to move forward from the grass toward the tarmac runway. As the aircraft reached the tarmac, it began to turn in a circle. During this maneuver, the left wing tip made contact with the ground, causing the aircraft to tip forward onto its nose. There were no injuries to the pilot, though the propeller was destroyed and the engine cowlings and wing tip sustained minor damage.
The investigation
The investigation established that the aircraft was not equipped with a parking brake. The pilot provided a statement indicating that he was attempting to prepare for takeoff before the airfield's Air Traffic Control services opened for the day. This time pressure led to the pilot failing to sufficiently tighten the throttle friction nut after starting the engine.
Findings
- The aircraft's movement was caused by the throttle vibrating towards the open position due to an insufficiently tightened friction nut.
- The pilot's desire to depart before the opening of ATC services contributed to the oversight.
- The aircraft's lack of a parking brake meant there was no secondary mechanism to prevent movement once the throttle moved.