What happened
On 6 November 2005, during daylight hours and in rainy conditions, a collision occurred in the holding area for Runway 27L at London Heathrow Airport. A Boeing 777-200, registration N781AN, was holding at position N2W behind a Boeing 737-800. Simultaneously, an Airbus A340-300, registration TC-JDK, was cleared to taxi to the N2E holding point.
As the Airbus A340-300 approached the Boeing 777-200, the crew of the A340 decided to taxi slightly to the left of the yellow taxiway centerline to provide more space between the two large aircraft. During this maneuver, the right winglet of the Airbus A340-300 struck the left elevator and left wing tip of the Boeing 777-200. Shortly after the first impact, the A340 experienced a second jolt as its wingtip made contact again with the B777's wingtip.
Following the impact, the pilot of the Boeing 777-200 notified Air Traffic Control that a collision had occurred. Both aircraft were directed to return to their stands for inspection. The Boeing 777-200 sustained damage to its left elevator and left wing tip, while the Airbus A340-300 suffered damage to its right winglet. There were no fatalities and no injuries to the crew or the hundreds of passengers on board the respective aircraft.
The investigation
The AAIB investigation examined ATC radio transmissions, ground radar, and flight data. The investigation found that the Air Departures Controller (ADC) had used the non-standard phrase "when you can" when instructing the A340 to taxi. The A340 crew, whose native language was not English, did not interpret this as a suggestion to proceed with caution. Furthermore, while the ADC transmitted a warning that the B777 would be moving shortly, this message was not acknowledged by the A340 crew.
The investigation also noted that the A340 crew was focused on the left side of the aircraft to monitor clearance from the grass, which hindered their ability to judge the distance to the B777. The investigation highlighted that the wingtips of large transport aircraft are notoriously difficult to monitor from the flight deck, even in good visibility.
Findings
- The Airbus A340-300 crew attempted to increase separation by taxiing left of the centerline, which inadvertently led to the collision.
- The use of non-standard ATC phraseology ("when you can") likely contributed to a misunderstanding of the required caution.
- The A340 crew did not hear or did not understand the ATC warning regarding the B777's imminent movement.
- Visual assessment of wingtip clearance is extremely difficult for pilots of large aircraft due to the obtuse angles and limited visibility from the cockpit.