What happened
On 21 April 2004, a Boeing 747-436, registration G-BNLG, arrived at London Heathrow Airport from San Francisco. As the aircraft was taxiing to its assigned parking position at Stand 127, the crew utilized the AGNIS guidance system and checked the area for obstructions. The flight crew observed that the airbridge appeared to be parked within its designated markings and proceeded to the stand.
During the final stages of parking, the aircraft's left wing struck the passenger airbridge. The impact caused a puncture to the leading edge of the port wing and resulted in debris being ingested into the No 2 engine, causing damage to the fan blades and acoustic liner. The collision was only halted after a member of the ground staff, observing the imminent impact from a terminal window, signaled the pilot to stop by crossing his arms. There were no fatalities or injuries among the 326 passengers or 18 crew members on board.
The investigation
The AAIB investigation established that the airbridge had been positioned in a circular parking area intended for smaller aircraft (Stand 127R) rather than the rectangular box required for a Boeing 747-436 at Stand 127. This discrepancy was linked to recent changes in the stand layout designed to increase airport capacity.
Investigators found that the dispatcher had been following updated operational instructions, but the documentation was subject to misinterpretation. Furthermore, the dispatcher was accustomed to seeing the airbridge in the circular position from previous operations. The investigation also highlighted that the dispatcher had no immediate way to alert the cockpit from the airbridge itself, as the emergency STOP light could only be activated from ground level, and no staff member had been assigned to monitor the ground-level switch during the aircraft's arrival.
Findings
- The airbridge was parked in the incorrect location, specifically in a zone designated for smaller aircraft.
- The airbridge was left in the wrong parking position due to a failure to follow updated operational instructions.
- The ground markings and the terminology used in safety instructions were confusing and prone to error.
- The dispatcher lacked a current reference copy of the updated operating procedures at the stand.
- There was no mechanism for the dispatcher to activate the aircraft's emergency stop light directly from the airbridge control station.
- The dispatcher's reliance on previous operational habits contributed to the incorrect positioning of the equipment.