What happened
On 8 February 2003, a Boeing 777-236, registration G-VIIU, arrived at London Heathrow from Chicago. Upon arrival at Stand W5, the aircraft was not fully positioned forward because the Azimuth Guidance for Nose-In Stand (AGNIS) system had not been activated. The commander notified Air Traffic Control (ATC) of the incomplete parking position and moved the aircraft forward once the guidance system was enabled.
Later that day, a Boeing 747-400 was being towed from Block 123 toward Stand X9. During this movement, the upper surface of the 747's port winglet struck the underside of the Boeing 777's left horizontal stabiliser. Neither the flight crew of the 777 nor the tow crew for the 747 realized a collision had occurred. The damage to the Boeing 777's left elevator trailing edge and stabiliser skin was discovered during a pre-flight inspection of the aircraft later that evening. Simultaneously, the 747 was found to have missing static wicks and damage to its winglet tip. Investigations by the operator confirmed the contact occurred near Stand W5.
The investigation
Investigators analyzed flight recorder data and ground movement radar, which confirmed that the two aircraft collided at 0708 hrs while both were moving forward. The investigation established that the tow crew had been cleared by ATC to move through the area adjacent to the W stands but had not been alerted to any potential obstructions. Furthermore, the crew's position on the taxiway centerline, combined with the slight camber of the taxiway, prevented them from observing that the Boeing 777 was not fully parked on its stand markings.
Findings
- The primary cause of the contact was the improper positioning of the Boeing 777 on its stand, as it had not been pulled fully forward.
- ATC failed to notify the tow crew of the aircraft's position.
- The tow crew could not visually identify that the Boeing 777 was obstructing the path due to their vantage point and the taxiway's camber.
- The damage remained undetected for several hours despite multiple scheduled inspections.