What happened
On 5 April 2009, a Stampe SV4C (registration G-BEPC) was involved in an accident at Chichester (Goodwood) Aerodrome. Following refueling, the pilot positioned the aircraft on the grass near the control tower. To initiate the engine start, the pilot performed a hand-swing of the propeller without anyone seated in the cockpit to monitor the engine.
Upon starting, the engine accelerated rapidly. The power generated was sufficient to overcome the handbrake, causing the aircraft to move forward and rotate around its right wheel. The aircraft briefly became airborne before striking trees along the western boundary of the airfield. The aircraft eventually came to rest beyond the western perimeter fence. The impact resulted in significant damage to the forward fuselage and wings, and the landing gear became detached, though no fire occurred.
The investigation
The investigation established that the aircraft was unoccupied during the start sequence. The pilot reported that while checking the cockpit controls from the rear seat, he likely manipulated the wrong lever. Specifically, the pilot believed he had closed the throttle, but instead moved the 'dummy' mixture lever, which is located immediately adjacent to the throttle. Because the mixture on this specific engine is permanently set to fully rich, the movement of this lever had no effect on the engine's fuel supply, leaving the throttle in the open position.
It was noted that the pilot may have left the throttle open following a previous flight shutdown. The investigation also highlighted that the lack of a briefed person in the cockpit prevented a timely reaction to the accelerating engine.
Findings
- The engine was started via hand-swinging the propeller while the cockpit was unoccupied.
- The pilot inadvertently left the throttle in the open position after mistakenly operating the non-functional mixture lever.
- The engine power produced during the start was enough to overcome the handbrake and initiate movement.
- The absence of a crew member in the cockpit meant there was no one to observe the engine's behavior and close the throttle immediately.