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Wing Tip Clearance Hazard

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Category: Ground Operations Ground Operations
Content source: SKYbrary About SKYbrary
Content control: EUROCONTROL EUROCONTROL

Description

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.

Swept Wing Growth
When the aircraft is pivoted on its main wheels, the wing tip and horizontal stabilizer clearance may decrease as the wing tip/tail surface arc or track moves outward[1].

References

  1. ^ NATA Safety 1st® eToolkit – Volume I, Issue 3 – October 15, 2004

Related Articles

Accidents and Serious Incidents

  • B738/B738, Girona Spain, 2010 (GND HF) (On 14 January 2010, two Ryanair Boeing 737-800 aircraft were operating scheduled passenger flights from Girona to Las Palmas and Turin respectively and had taxied from adjacent gates at Girona in normal day visibility in quick succession. The Turin-bound aircraft taxied first but because it was early at the holding point for its CTOT, the other aircraft was designated first for take off and during the overtaking manoeuvre in the holding area, the wing tip of the moving Las Palmas aircraft hit the horizontal stabiliser of the Turin bound aircraft causing minor and substantial damage to the respective aircraft. None of the respective 81 and 77 occupants were injured and both aircraft taxied back to their gates.)
  • B738 / B738, Seville Spain, 2012 (GND HF) (On 13 April 2012 a Boeing 737-800 being taxied off its parking stand for a night departure by the aircraft commander failed to follow the clearly and correctly marked taxi centrelines on the well-lit apron and instead took a short cut towards the taxiway centreline which resulted in the left winglet striking the left horizontal stabiliser and elevator of another Ryanair aircraft correctly parked on the adjacent stand causing damage which rendered both aircraft unfit for flight. The pilot involved was familiar with the airport and had gained almost all his flying experience on the accident aircraft type.)
  • 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.)
  • B74S, Stockholm Arlanda Sweden, 2006 (GND HF) (On 11 December 2006, a Boeing 747SP being operated by Syrian Air on a scheduled passenger flight from Damascus to Stockholm was arriving on the designated parking gate at destination in normal visibility at night when it collided with the airbridge. None of the 116 occupants of the aircraft suffered any injury but the aircraft was “substantially damaged” and the airbridge was “damaged”.)
  • 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.)
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