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Taxiway Collisions

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Category: Ground Operations Ground Operations
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Description

An airport is a complex interface between the air and the ground environments, where access must be controlled and separation between aircraft or between aircraft and vehicular traffic must be maintained and optimised. While most occurrences on airport aprons and taxiways do not have consequences in terms of loss of life, they are often associated with aircraft damage, delays to passengers and avoidable financial costs.

This article examines collisions and near collisions whilst aircraft are on the airport manoeuvring areas inclusive of taxiways and ramp areas. The article On-Gate Collisions provides insight into aircraft collisions occurring whilst on, entering or leaving an assigned gate.

Occurrences

As previously stated, to ensure efficient and safe airport ground operations, separation between aircraft or between aircraft and vehicular traffic must be maintained and optimised. On occasion, however, minimum separation, particularly aircraft/vehicle separation is compromised. Whilst all events do not result in collision with an aircraft, the majority of taxiway occurrences involve vehicle operators deviating from a surface movement controller clearance. These "failure to comply" occurrences most usually involve vehicles:

  • using an incorrect taxiway
  • failing to stop at a taxiway holding point
  • failing to stay on the surface movement control radio frequency or ground frequency as appropriate
  • failing to obtain a clearance before entering an area subject to control.

In all cases, these actions have the potential to put the vehicle in conflict with an aircraft which, in turn, could:

  • lead to collision
  • require aggressive braking by the aircraft which could result in personnel injuries. Cabin crew are especially vulnerable as they might be moving within the cabin preforming pre-departure or post-landing duties


Most of the remaining occurrences are related to one of the following:

  • aircraft-aircraft collisions or near collisions - collisions can result from:
    • failure to follow taxiway centreline guidance
    • failure to stop prior to a stopbar
    • taxiing at speeds unsuited to the conditions or level of congestion
    • taxiway deviation whilst trying to manoeuvre to "squeeze" past another aircraft. Manoeuvring around an aircraft partially blocking a taxiway (as might be the case if the aircraft was approaching, but not yet at the stop point of, a gate) can lead to collision. If misjudged, this could result in a wingtip striking the tail of the stopped aircraft or it could compromise clearance between obstacles or other aircraft and the wingtip opposite the stopped aircraft
    • taxiway configuration - converging taxiways can potentially lead to reduced or compromised clearance, especially where they cross
  • reduced aircraft clearance with ground equipment or obstacles. Reduced clearance accidents or incidents can occur in various ways. These include:
    • inappropriate use of a restricted taxiway - some taxiways are restricted by wingspan. Use by a larger aircraft could compromise obstacle clearance
    • failure to follow taxi lane guidance - deviation from the lane guidance whilst manoeuvring in proximity to light stands, gates or stationary equipment can result in collision
  • jet blast -inappropriate thrust settings or following too closely can result in aircraft damage due to jet blast. Jet blast can also cause unsecured equipment such as Unit Load Devices (ULD) to move and strike other aircraft, equipment or personnel

Prevention

Most taxiway accidents and incidents are preventable. This prevention is dependant upon appropriate training and testing, compliance with clearances, published procedures and right-of-way rules, maintaining situational awareness and adapting speed of movement to suit the weather and surface conditions. Some specific accident prevention strategies are as follows:

  • Vehicle operators - It is imperative that vehicle operators be properly trained, tested and authorised for ramp and taxiway operations. Driving infractions should be investigated and additional training provided where appropriate. Multiple infractions should be considered grounds for suspension of airside driving privileges. Operators should:
    • ensure daily inspection for their vehicle is complete and that beacon/hazard lights are operating when the vehicle is airside
    • maintain situational awareness
    • operate their vehicle safely and in accordance with all company and airport rules
    • obey all "rules of the road" inclusive of speed limits, stop signs and right-of-way guidance
    • yield to aircraft at all times
    • obtain and read back any ground movement controller clearance prior to entering an area where clearance is required. If clearance is not understood, ASK!
  • Tug operators - Tug operators have the additional responsibility of moving aircraft on and off gates as well as positioning aircraft from one location on the airfield to another. In addition to the aforementioned items for vehicle operators, the tug operator must:
    • know the size of the aircraft in tow inclusive of the wingspan
    • be conversant with the normal taxi routes from one airfield location to another
    • understand the stopping distances required for a tug with an aircraft in tow
    • comply with all clearances, especially runway crossing clearances
    • use wing and tail walkers when manoeuvring in congested areas
  • Controllers - The ground controller is responsible for the safe and efficient movement of aircraft and vehicle traffic on the taxiways and aprons. They should:
    • provide the appropriate clearance for the requested action
    • ensure that the clearance readback is accurate
    • to the extent possible, monitor the movement visually, via transponder or by use of multilateration equipment to ensure clearance compliance
  • Pilots - In general, pilots are responsible for the ground movement of an aircraft from the runway to the gate and from the gate to the runway although they may also reposition aircraft from one point on the airfield to another. In all cases they should:
    • request, readback and comply with an appropriate clearance
    • maintain situational awareness
    • taxi at a speed appropriate to the conditions and traffic situation
    • maintain the centre of the taxi lane
    • be vigilant for taxi lane compromise by another aircraft, vehicle or object
    • not assume that vehicles will yield right-of-way

Accidents and Incidents

The following accidents and incidents involve collision or near collision between two aircraft, an aircraft and a vehicle, or an aircraft and a stationary object.

Aircraft/Aircraft Conflict

  • CRJ7 / CRJ2, Charlotte NC USA, 2008 (On 28 June 2008, a Bombardier CRJ 700 operated by PSA Airlines, during daytime pushback collided with a stationary CRJ 200 of the same company at Douglas International Airport Charlotte, North Carolina.)
  • MD82 / C441, Lambert-St Louis MI USA, 1994 (On 22 November 1994 a McDonnell Douglas MD 82 flight crew taking off from Lambert- St. Louis at night in excellent visibility suddenly became aware of a stationary Cessna 441 on the runway ahead and was unable to avoid a high speed collision. The collision destroyed the Cessna but allowed the MD82 to be brought to a controlled stop without occupant injury. The Investigation found that the Cessna 441 pilot had mistakenly believed his departure would be from the runway he had recently landed on and had entered that runway without clearance whilst still on GND frequency.)
  • DH8C / P180, Ottawa ON Canada, 2013 (On 1 December 2013, a small aircraft taxing for departure at night was cleared to cross an active runway and did so as a DHC8 was taking off from the same runway. Separation was significant and there was no actual risk of collision. The Investigation found that the GND controller had issued clearance to the taxiing aircraft when he had responsibility for its whole taxi route but had neither updated the aircraft status system nor directly advised of the taxiing aircraft when passing responsibility for part of its cleared route to the TWR controller who therefore remained unaware of it.)
  • SH33 / MD83, Paris CDG France, 2000 (On the 25th of May, 2000 a UK-operated Shorts SD330 waiting for take-off at Paris CDG in normal visibility at night on a taxiway angled in the take-off direction due to its primary function as an exit for opposite direction landings was given a conditional line up clearance by a controller who had erroneously assumed without checking that it was at the runway threshold. After an aircraft which had just landed had passed, the SD330 began to line up unaware that an MD83 had just been cleared in French to take off from the full length and a collision occurred.)
  • B738 / B738, Dublin Ireland, 2014 (On 7 October 2014, a locally-based Boeing 737-800 taxiing for departure from runway 34 at Dublin as cleared in normal night visibility collided with another 737-800 stationary in a queue awaiting departure from runway 28. Whilst accepting that pilots have sole responsible for collision avoidance, the Investigation found that relevant restrictions on taxi clearances were being routinely ignored by ATC. It also noted that visual judgement of wingtip clearance beyond 10 metres was problematic and that a subsequent very similar event at Dublin involving two 737-800s of the same Operator was the subject of a separate investigation.)
  • B742 / B741, Tenerife Canary Islands Spain, 1977 (On 27 March 1977, a KLM Boeing 747-200 began its low visibility take-off at Tenerife without requesting or receiving take-off clearance and a collision with a Boeing 747-100 backtracking the same runway subsequently occurred. Both aircraft were destroyed by the impact and consequential fire and 583 people died. The Investigation attributed the crash primarily to the actions and inactions of the KLM Captain, who was the Operator's Chief Flying Instructor. Safety Recommendations made emphasised the importance of standard phraseology in all normal radio communications and avoidance of the phrase "take-off" in ATC Departure Clearances.)
  • DC91 / B722, Detroit MI USA, 1990 (On 3 December 1990 a Douglas DC9-10 flight crew taxiing for departure at Detroit in thick fog got lost and ended up stopped to one side of an active runway where, shortly after reporting their position, their aircraft was hit by a departing Boeing 727-200 and destroyed by the impact and subsequent fire. The Investigation concluded that the DC9 crew had failed to communicate positional uncertainty quickly enough but that their difficulties had been compounded by deficiencies in both the standard of air traffic service and airport surface markings, signage and lighting undetected by safety regulator oversight.)
  • B752 / CRJ7, San Francisco CA USA, 2008 (On 13 January 2008, a Boeing 757-200 and a Bombardier CL-600 received pushback clearance from two adjacent terminal gates within 41 seconds. The ground controller believed there was room for both aircraft to pushback. During the procedure both aircraft were damaged as their tails collided. The pushback procedure of the Boeing was performed without wing-walkers or tail-walkers.)

Aircraft/Vehicle Conflict

  • SB20, Stockholm Arlanda, 2001 (On 18 December 2001, a Saab 2000 being operated by Air Botnia on scheduled passenger flight from Stockholm to Oulu was taxiing out at night in normal visibility in accordance with its ATC clearance when a car appeared from the left on a roadway and drove at speed on a collision course with the aircraft. In order to avoid a collision, the aircraft had to brake sharply and the aircraft commander saw the car pass under the nose of the aircraft and judged the vehicle’s closest distance to the aircraft to be four to five metres. The car did not stop, could not subsequently be identified and no report was made by the driver or other witnesses. The diagram below taken from the official report shows the site of the conflict - the aircraft was emerging from Ramp ‘G’ to turn left on taxiway ‘Z’ and the broken line shows the roadway which is crossed just before the left turn is commenced.)
  • A320, London Heathrow UK, 2006 (On 26 June 2006, after an uneventful pre-flight pushback of a British Airways Airbus A320-200 at London Heathrow Airport, the aircraft started moving under its own power and, shortly afterwards, collided with the tractor that had just performed the pushback, damaging both the right engine and the tractor.)
  • B738, London Stansted UK, 2008 (On 13 November 2008, a Boeing 737-800 with an unserviceable APU was being operated by Ryanair on a passenger flight at night was in collision with a tug after a cross-bleed engine start procedure was initiated prior to the completion of a complex aircraft pushback in rain. As the power was increased on the No 1 engine in preparation for the No 2 engine start, the resulting increase in thrust was greater than the counter-force provided by the tug and the aircraft started to move forwards. The towbar attachment failed and subsequently the aircraft’s No 1 engine impacted the side of the tug, prior to the aircraft brakes being applied.)
  • E190 / Vehicle, Paris CDG France, 2014 (On 19 April 2014, an Embraer 190 collided with the tug which was attempting to begin a pull forward after departure pushback which, exceptionally for the terminal concerned, was prohibited for the gate involved. As a result, severe damage was caused to the lower fuselage. The Investigation found that the relevant instructions were properly documented but ignored when apron services requested a 'push-pull' to minimise departure delay for an adjacent aircraft. Previous similar events had occurred on the same gate and it was suspected that a lack of appreciation of the reasons why the manoeuvre used was prohibited may have been relevant.)
  • Vehicle / PA31, Mackay SE Australia, 2008 (On 29 June 2012, a Piper PA31 taking off from runway 05 on a passenger charter flight just missed hitting an inspection vehicle which had entered the take off runway from an intersecting one contrary to ATC clearance. The overflying aircraft was estimated to have cleared the vehicle by approximately 20 feet and the pilot was unaware it had entered the active runway. The driver had been taking a mobile telephone call at the time and attributed the incursion to distraction. The breached clearance had been given and correctly read back approximately two minutes prior to the conflict occurring.)
  • B737, Gran Canaria Spain, 2016 (On 7 January 2016, a Boeing 737-700 was inadvertently cleared by ATC to take off on a closed runway. The take-off was commenced with a vehicle visible ahead at the runway edge. When ATC realised the situation, a 'stop' instruction was issued and the aircraft did so after travelling approximately 740 metres. Investigation attributed the controller error to "lost situational awareness". It also noted prior pilot and controller awareness that the runway used was closed and that the pilots had, on the basis of the take-off clearance crossed a lit red stop bar to enter the runway without explicit permission.)
  • A320, Dublin Ireland, 2017 (On 27 September 2017, an Airbus A320 being manoeuvred off the departure gate at Dublin by tug was being pulled forward when the tow bar shear pin broke and the tug driver lost control. The tug then collided with the right engine causing significant damage. The tug driver and assisting ground crew were not injured. The Investigation concluded that although the shear pin failure was not attributable to any particular cause, the relative severity of the outcome was probably increased by the wet surface, a forward slope on the ramp and fact that an engine start was in progress.)
  • FA50 / Vehicle, Moscow Vnukovo Russia, 2014 (On 20 October 2014 a Dassault Falcon 50 taking off at night from Moscow Vnukovo collided with a snow plough which had entered the same runway without clearance shortly after rotation. Control was lost and all occupants died when it was destroyed by impact forces and post crash fire. The uninjured snow plough driver was subsequently discovered to be under the influence of alcohol. The Investigation found that the A-SMGCS effective for over a year prior to the collision had not been properly configured nor had controllers been adequately trained on its use, especially its conflict alerting functions.)

Aircraft/Object Conflict

  • A319, London Heathrow UK, 2007 (On 12 February 2007, an Airbus A319-100 being operated by British Airways on a scheduled passenger flight into London Heathrow made unintended contact in normal daylight visibility with the stationary airbridge at the arrival gate. This followed an emergency stop made after seeing hand signals from ground staff whilst following SEGS indications which appeared to suggest that there was a further 5 metres to run to the correct parking position. There was no damage to the aircraft, only minimal damage to the airbridge and there were no injuries to the aircraft occupants or any other person)
  • B738, Barcelona Spain, 2015 (On 12 December 2015, whilst a Boeing 737-800 was beginning disembarkation of passengers via an air bridge which had just been attached on arrival at Barcelona, the bridge malfunctioned, raising the aircraft nose gear approximately 2 metres off the ground. The door attached to the bridge then failed and the aircraft dropped abruptly. Prompt cabin crew intervention prevented all but two minor injuries. The Investigation found that the occurrence had been made possible by the failure to recognise new functional risks created by a programme of partial renovation being carried out on the air bridges at the Terminal involved.)
  • AT72, Shannon Ireland, 2014 (On 26 February 2014, an ATR 72-202 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.)
  • A319, Ibiza Spain, 2016 (On 19 June 2016, an Airbus A320 failed to follow the clearly-specified and ground-marked self-positioning exit from a regularly used gate at Ibiza and its right wing tip collided with the airbridge, damaging both it and the aircraft. The Investigation found that the crew had attempted the necessary left turn using the Operator’s ‘One Engine Taxi Departure’ procedure using the left engine but then failed to follow the marked taxi guideline by a significant margin. It was noted that there had been no other such difficulties with the same departure in the previous four years it had been in use.)
  • B737, Amsterdam Netherlands, 2003 (n 22 December 2003, a Boeing 737-700 being operated by UK Operator Easyjet on a scheduled passenger flight from Amsterdam to London Gatwick was taxiing for departure at night in normal visibility and took a different route to that instructed by ATC. The alternative route was, unknown to the flight crew, covered with ice and as a consequence, an attempt to maintain directional control during a turn was unsuccessful and the aircraft left wing collided with a lamp-post. The collision seriously damaged the aircraft and the lamp post. One passenger sustained slight injuries because of the impact. The diagram below taken from the official investigation report shows the area where the collision occurred.)
  • B722, Cotonou Benin, 2003 (On 25 December 2003, a Boeing 727-200 being operated by UTA (Guinea) on a scheduled passenger flight from Cotonou to Beirut with a planned stopover at Kufra, Libya, failed to get properly airborne in day VMC from the 2400 metre departure runway and hit a small building 2.45 metres high situated on the extended centreline 118 metres beyond the end of the runway. The right main landing gear broke off and ripped off a part of the trailing edge flaps on the right wing. The airplane then banked slightly to the right and crashed onto the beach where it broke into several pieces and ended up in the sea where the depth of water varied between three and ten metres. Of the estimated 163 occupants, 141 were killed and the remainder seriously injured.)
  • B738, Surat India, 2014 (On 6 November 2014, a Boeing 737-800 taking off at night from Surat hit an object as it was approaching 80 knots and the take-off was immediately rejected. On return to the gate substantial damage was found to the left engine and a runway inspection found one dead buffalo and another live one. The runway was reopened after removal of the carcass but the live buffalo was not removed and was seen again by the runway the following day. The Investigation found a history of inadequate perimeter fencing and inadequate runway inspection practices at the airport.)
  • B74S, Stockholm Arlanda Sweden, 1996 (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”.)

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