Incident Overview
On 22 November 2006 at 0725 UTC, a Boeing 747-436 (registration G-BNLE) was parked on Stand 430 at London Heathrow Airport following a scheduled flight from São Paulo. In preparation for passenger disembarkation, a self-propelled passenger stair vehicle was positioned at the No 2 left aircraft door.
Sequence of Events
After the stair head was placed against the aircraft's door sill, the vehicle operative extended the hydraulically powered stabilisation jacks. As these jacks extended, the two 'stair height' hydraulic jacks retracted. This allowed the lower forward edge of the stair head to descend into the honeycomb fuselage-to-wing fairing, where it came to rest, resulting in a hole in the fairing.
Injuries and Damage
No injuries were reported among the crew or passengers. The only damage was a hole in the fuselage-to-wing fairing.
Investigation
The AAIB conducted a field investigation. An engineering examination by the equipment operator and manufacturer found that an electrical component failure had occurred within the stair vehicle's hydraulic system. The manufacturer subsequently introduced a modification to prevent recurrence, and the operator planned to apply the modification to its entire fleet of these vehicles.