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Wing Tip Clearance Hazard

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Article Information
Category: Ground Operations Ground Operations
Content source: SKYbrary About SKYbrary
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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

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Accidents and Serious Incidents

  • B74S, Stockholm Arlanda Sweden, 1996 (GND HF) (On 14 June 1996, a Boeing 747SP being operated by Air China on a scheduled passenger flight from Beijing to Stockholm was arriving on the designated parking gate at destination in normal daylight visibility when it collided with the airbridge. None of the 130 occupants of the aircraft suffered any injury but the aircraft was “substantially damaged” and the airbridge was “damaged”.)
  • AT72, Shannon Ireland, 2014 (GND HF) (On 26 February 2014, an ATR 72-200 which had been substituted for the ATR42 which usually operated a series of night cargo flights was being marshalled out of its parking position with a new flight crew on board when the left wing was in collision with the structure of an adjacent hangar. The Investigation found that the aircraft type had not been changed on the applicable flight plan and ATC were consequently unaware that the aircraft had previously been parked in a position only approved for the use by the usual smaller aircraft type.)
  • B744 / B763, Melbourne Australia, 2006 (GND HF) (On 2 February 2006, a Boeing 747-400 was taxiing for a departure at Melbourne Airport. At the same time, a Boeing 767-300 was stationary on taxiway Echo and waiting in line to depart from runway 16. The left wing tip of the Boeing 747 collided with the right horizontal stabiliser of the Boeing 767 as the first aircraft passed behind. Both aircraft were on scheduled passenger services from Melbourne to Sydney. No one was injured during the incident.)
  • A321, Daegu South Korea, 2006 (GND HF) (On 21 February 2006, an Airbus A321-200 being operated by China Eastern on a scheduled passenger flight from Daegu to Shanghai Pudong failed to follow the marked taxiway centreline when taxiing for departure in normal daylight visibility and a wing tip impacted an adjacent building causing minor damage to both building and aircraft. None of the 166 occupants were injured.)
  • A332/A345, Khartoum Sudan, 2010 (GND HF) (On 30 September 2010, an Airbus 330-200 being operated by KLM on a passenger fight from Khartoum to Abu Dhabi UAE taxied for departure along the main taxiway parallel to the runway in normal night ground visibility and when passing behind a parked Airbus A340-500 with passengers on board hit the lower empennage of that aircraft with its left wing tip without awareness of any impact. When the A340 crew reported the impact a few minutes later after detecting an abnormal jolt and losing the APU function and the services it was providing, the A330 had just been given take off clearance and was about to roll. Signalling from a hand held flashlight and the radio call from the A340 resulted in the A330 holding position and shutting down for a tow back to the Terminal. None of the 142 occupants on the A330 or any of those on the A340 were injured.)
  • … further results