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Wing Tip Clearance Hazard
Taxiways are designated for use by all or only some aircraft types. Provided ATC do not make errors in issuing taxi clearance and aircraft flight crew comply with clearances or standard routings, the greatest risk of wing tip collision is present when aircraft are holding or manoeuvring, for example on the approach to the runway entry point. Large Aircraft where the wing tip may not be visible to the pilots, may have to manoeuvre, sometimes at night, to change the queuing order. Such movement often needs to be carried out without taxiway centrelines to follow.
The responsibility for aircraft safety when taxying remains wholly with each aircraft commander. Sometimes, the potential hazard of wingtip collision is known to the airport operators, who may mitigated their liability by ATIS or NOTAM statements such as “wingtip clearance is not assured”.
Examples of the way in which wing tip collision has occurred can be found in the reports on the serious incidents listed under below.
All the aircraft involved in these occurrences were, like most modern transport aircraft, swept wing types which are subject to a phenomenon known as ‘swept wing growth’ or ‘wing creep’. This occurs during a turn when the wing tip describes an arc greater than the normal wingspan due to the geometry of the aircraft and the arrangement of the landing gear. It is one of the reasons for the manufacturer’s cautions usually found in the Flight Crew Training Manuals. Although the effect is less noticeable at moderate curvature of turn, it still serves to erode the perceived wing tip clearance in any turn.
- ^ NATA Safety 1st® eToolkit – Volume I, Issue 3 – October 15, 2004
Accidents and Serious Incidents
- A343 / B752, London Heathrow UK, 1995 (GND HF) (On 23 November 1995, in normal daylight visibility, an Airbus A340-300 being operated by Gulf Air on a scheduled international passenger flight from London Heathrow taxied past a Boeing 757-200 being operated by British Airways on a scheduled domestic passenger flight and also departing from London Heathrow which had stopped on a diverging taxiway within the departure holding area for Runway 27R such that the wing tip of the Airbus impacted the tail fin of other aircraft. Two of the 378 occupants of the two aircraft suffered minor injuries and both aircraft were damaged. Passengers were deplaned uneventfully from both aircraft.)
- B738/A321, Prague Czech Republic, 2010 (GND HF) (On 18 June 2010 a Sun Express Boeing 737-800 taxiing for a full length daylight departure from runway 06 at Prague was in collision with an Airbus 321 which was waiting on a link taxiway leading to an intermediate take off position on the same runway. The aircraft sustained damage to their right winglet and left horizontal stabiliser respectively and both needed subsequent repair before being released to service.)
- A124, Zaragoza Spain, 2010 (GND HF) (On 20 April 2010, the left wing of an Antonov Design Bureau An124-100 which was taxiing in to park after a night landing at Zaragoza under marshalling guidance was in collision with two successive lighting towers on the apron. Both towers and the left wingtip of the aircraft were damaged. The subsequent investigation attributed the collision to allocation of an unsuitable stand and lack of appropriate guidance markings.)
- A319, London Heathrow UK, 2007 (GND HF) (On 12 February 2007, an Airbus A319-100 being operated by British Airways on a scheduled passenger flight into London Heathrow made unintended contact in normal daylight visibility with the stationary airbridge at the arrival gate. This followed an emergency stop made after seeing hand signals from ground staff whilst following SEGS indications which appeared to suggest that there was a further 5 metres to run to the correct parking position. There was no damage to the aircraft, only minimal damage to the airbridge and there were no injuries to the aircraft occupants or any other person)
- B744 / A321, London Heathrow UK, 2004 (GND HF) (On 23 March 2004, an out of service British Airways Boeing 747-400, under tow passed behind a stationary Airbus A321-200 being operated by Irish Airline Aer Lingus on a departing scheduled passenger service in good daylight visibility and the wing tip of the 747 impacted and seriously damaged the rudder of the A321. The aircraft under tow was cleared for the towing movement and the A321 was holding position in accordance with clearance. The towing team were not aware of the collision and initially, there was some doubt in the A321 flight deck about the cause of a ‘shudder’ felt when the impact occurred but the cabin crew of the A321 had felt the impact shudder and upon noticing the nose of the 747 appearing concluded that it had struck their aircraft. Then the First Officer saw the damaged wing tip of the 747 and informed ATC about the possible impact. Later another aircraft, positioned behind the A321, confirmed the rudder damage. At the time of the collision, the two aircraft involved were on different ATC frequencies.)
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