What happened
On 29 July 2009, a Boeing 747-436, registration G-BNLA, was taxiing to Stand 409 at London Heathrow Airport following a commercial flight from Singapore. As the aircraft turned onto the stand, the commander observed that the lateral guidance of the Aircraft Parking Information System (APIS) was illuminated. However, the distance-to-stop indication was not functioning.
While the commander was monitoring the guidance, the aircraft passed 11 metres beyond its intended stopping point. During this maneuver, the outboard cowling of the number one engine made contact with a metal baggage container that had been incorrectly parked and was protruding into the active stand area. The impact resulted in minor damage to the engine cowling, specifically a small dent and paint abrasion.
The investigation
The investigation established that the APIS lateral guidance board was illuminated due to a wiring defect in the lateral guidance module, even though the system had not been activated. This defect caused the pilot to believe the system was functioning correctly.
Furthermore, the investigation found that the commander had not reviewed the aircraft type bar on the display, which would have indicated that the system was not properly set. The Turn Round Manager (TRM) attempted to signal the pilot to stop using hand signals, but these were not seen by the crew. The TRM eventually activated the emergency stop button after the aircraft continued moving.
Findings
- A wiring defect in the APIS lateral guidance module caused the lateral guidance to remain illuminated despite the system being inactive.
- A baggage container was incorrectly positioned, protruding into the parking stand area.
- The commander did not observe the protruding container because it was likely obscured by other vehicles and equipment.
- The commander did not check the aircraft type display, which would have revealed the system was not activated.
- The Turn Round Manager's visual signals were not observed by the flight crew.