What happened
On 17 March 2006, a Learjet 45, registration D-CNIK, was being prepared for a flight to Paris at London Gatwick Airport. The aircraft was parked at Stand 143 with the right engine running to provide electrical power and air conditioning for the cabin. While the co-pilot was on the flight deck, the commander was at the rear of the cabin stowing baggage.
During the engine start sequence, the right engine power was inadvertently increased to 70% N1. This caused the aircraft to move forward, unobserved by the co-pilot. As the aircraft progressed, the left wing struck a parked Volkswagen Sharan multi-purpose vehicle. The impact caused the aircraft to swing rapidly to the left, eventually coming to rest against the side of the vehicle. During the movement, the commander was knocked from the open aircraft doorway and sustained serious injuries.
The investigation
The AAIB investigation examined the aircraft's braking system and engine control data. Flight data recorder analysis revealed that the No 2 engine thrust lever was advanced to approximately 80% N1 before being returned to idle. The investigation also looked into the effectiveness of the parking brake and the adequacy of the chocks in place. It was noted that the wooden chocks used were relatively light and could be displaced by significant force.
Investigators also reviewed the operator's checklists. The existing 'Before Starting Engines' checklist was found to be lengthy and not specifically tailored for ground service operations where an engine is run solely for air conditioning. Furthermore, the procedure to ensure the parking brake was properly charged via the auxiliary hydraulic pump was not explicitly followed by the crew.
Findings
- The aircraft moved due to an unintended increase in right engine thrust.
- The co-pilot was not in a position to apply the brakes immediately when the movement began.
- The use of light wooden chocks provided insufficient resistance to the engine's thrust.
- The lack of a specific checklist for engine start during ground servicing increased the risk of procedural errors.
- The noise from the air conditioning system likely prevented the commander from hearing the co-pilot's attempts to call out the movement.