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Wing Tip Clearance Hazard

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Category: Ground Operations Ground Operations
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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

  • 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.)
  • 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.)
  • 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”.)
  • A343 / B744, London Heathrow UK, 2007 (GND HF) (On 15 October 2007, an Airbus 340-300 being operated on a scheduled passenger flight by Air Lanka with a heavy crew in the flight deck was taxiing towards the departure runway at London Heathrow at night in normal visibility when the right wing tip hit and sheared off the left hand winglet of a stationary British Airways Boeing 747-400 which was in a queue on an adjacent taxiway. The Airbus 340 sustained only minor damage to the right winglet and navigation light.)
  • 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.)
  • … further results
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