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Wing Tip Clearance Hazard
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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
- B744, Paris CDG France, 2003 (GND HF) (On 18 January 2003, a Boeing 747-400F being operated by Singapore Airlines Cargo on a scheduled cargo flight from Paris CDG to Dubai taxied for departure in darkness and fog with visibility less than 100 metres in places and the right wing was in collision with a stationary and unoccupied ground de/anti icing vehicle without the awareness of either the flight crew or anybody else at the time. Significant damage occurred to the de icing vehicle and the aircraft was slightly damaged. The vehicle damage was not discovered until almost two hours later and the aircraft involved was not identified until it arrived in Dubai where the damage was observed and the authorities at Paris CDG advised.)
- 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”.)
- MD82 / MD11, Anchorage AK USA, 2002 (GND HF) (On 17 March 2002, at Ted Stevens Anchorage Airport, a McDonnell Douglas MD82 operated by Alaska Airlines, on a night pushback in snow conditions collided with an inbound taxiing McDonnell Douglas MD-11. The MD82 suffered substantial rudder damage although the impacting MD11 winglet was undamaged.)
- 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.)
- DH8C / GALX, Valencia Spain, 2008 (HF GND) (On 11 February 2008, the crew of a DHC8-300 misjudged the sufficient clearance during taxi and collided with a Gulfstream G200 at a taxiway intersection.)
- … further results