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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
- 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.)
- B738/B763, Barcelona Spain, 2011 (GND HF) (On 14 April 2011, a Ryanair Boeing 737-800 failed to leave sufficient clearance when taxiing behind a stationary Boeing 767-300 at Barcelona and the 737 wingtip was in collision with the horizontal stabiliser of the 767, damaging both. The 767 crew were completely unaware of any impact but the 737 crew realised the ‘close proximity’ but dismissed a cabin crew report that a passenger had observed a collision. Both aircraft completed their intended flights without incident after which the damage was discovered, that to the 767 requiring that the aircraft be repaired before further flight.)
- 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.)
- 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.)
- RJ85 / RJ1H, London City Airport, London UK, 2008 (GND HF) (On 21 April 2008, an Avro RJ85 aircraft was parked on Stand 10 at London City Airport, with an Avro RJ100 parked to its left, on the adjacent Stand 11. After being repositioned by a tug, the RJ85 taxied forward and to the right, its tail contacting the tail of the RJ100 and causing minor damage to the RJ100’s right elevator.)
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