What happened
On 2 September 1999, a Boeing 747-SP, registration YK-AHA, was positioned at Stand G12 at London Heathrow Airport for a passenger flight. While the aircraft was stationary and passengers were in the process of boarding, a ground service vehicle was maneuvering near the aft cargo bay door. During this process, the vehicle reversed into the aircraft's number four engine exhaust tail cone.
During a routine external inspection of the aircraft, the flight engineer identified a vertical dent measuring 29 cm on the outboard side of the engine's exhaust cone. There were no injuries to the 110 passengers or the 13 crew members on board.
The investigation
The investigation established that the damage was caused by a loading vehicle performing a reversing maneuver. The vehicle was operating without the assistance of an external guide to monitor its clearance from the aircraft. Following the discovery of the dent, the aircraft was taken to a maintenance organisation where the necessary repairs were completed before the aircraft was returned to service.