What happened
On 1 February 2008, a Fokker F27 Mk 500 Friendship, registration TC-MBG, was prepared for a night cargo flight from Edinburgh to Coventry. Due to wintry conditions and snowfall, the aircraft had undergone de-icing, which caused a delay in its scheduled departure. After the crew had started both engines, the commander signaled for the ground crew to disconnect the Ground Power Unit (GPU).
As the marshaller moved to assist a colleague in relocating the GPU, the aircraft began to move forward slowly. The flight crew, focused on the 'After Start' checklist, were unaware of the movement. The aircraft continued down a slight 1.5% slope until the right propeller struck the GPU. The impact caused substantial damage to the propeller, the engine, and the GPU itself. The right engine nacelle was nearly separated from the wing, and the impact also damaged a window transparency. No injuries were reported among the three crew members.
The investigation
The AAIB investigation examined the aircraft's position, the ground conditions, and the cockpit voice recorder. The aircraft had been repositioned to face into the wind to protect the tail, which placed it facing nose-out and down a slight slope. Investigators found that while the commander believed the parking brake was set, there was no verbal confirmation on the cockpit voice recorder. Furthermore, while the marshaller believed the nosewheel was chocked, the airport fire and rescue services found no chocks near the wheels upon their arrival, although some were later found in the GPU wreckage.
Findings
- The aircraft was positioned facing down a slight slope.
- The ramp surface was slippery due to the wintry weather.
- The aircraft was facing nose-out on the North Cargo Apron, contrary to airport safety directives which required such aircraft to be towed to the taxiway centerline before engine start.
- The flight crew increased engine power to attempt to restore pneumatic system pressure, which may have contributed to the movement.
- There was insufficient evidence to confirm whether the parking brake was set, if the chocks had slipped, or if they had been removed prematurely.