If you wish to contribute or participate in the discussions about articles you are invited to join SKYbrary as a registered user

 Actions

On-Gate Collisions

From SKYbrary Wiki

Revision as of 09:57, 28 June 2018 by Editor1 (talk | contribs) (Editor1 moved page Work in progress:On-Gate Collisions to On-Gate Collisions without leaving a redirect)
(diff) ← Older revision | Latest revision (diff) | Newer revision → (diff)
Article Information
Category: Ground Operations Ground Operations
Content source: SKYbrary About SKYbrary
Content control: SKYbrary About SKYbrary

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 whilst aircraft are on, approaching or departing their assigned gate. The article Taxiway Collisions provides insight into collisions occurring on the airport taxiway environment.

Approaching Gate Occurrences

The aircraft can approach the gate either under its own power or under tow. Although collisions during the parking process most often occur as a result of the aircraft striking items in its path, it is also possible that the aircraft itself could be struck by support vehicles, improperly secured equipment or by other aircraft, either manoeuvring or under tow. Some of the more commonly encountered causes of collisions include:

  • Failure to follow lead-in guidance - "cutting the corner" whilst approaching a gate can cause a wingtip to strike an aircraft on an adjacent gate
  • Inappropriate gate assignment - not all gates can accommodate all aircraft types. If the gate assigned is too small for the aircraft type, the aircraft could strike airport infrastructure, equipment outside of the safety zone or aircraft on adjacent gates
  • Inappropriate stop guidance or failure to stop when directed - a late stop can result in the aircraft striking the Passenger Boarding Bridge or other support equipment
  • Vehicle traffic failing to yield right-of-way to aircraft - this action can lead to a collision but is even more likely to result in harsh braking action by the aircraft and potential personnel injuries
  • Compromised safety zone- vehicles or equipment positioned within the gate's aircraft safety zone may be struck as the aircraft approaches the stop point
  • Compromised taxiway clearance - there are numerous reasons that a parking aircraft might stop short of the gate (lack of marshaller, inappropriate automated guidance, safety zone violations, etc). However, in doing so, the taxiway behind the aircraft may be compromised and there is risk that another taxiing aircraft could strike the tail of the one in the process of parking
  • Premature positioning of support equipment - no personnel or equipment should approach the aircraft until the aircraft beacon has been turned off, indicating that it is safe to do so. Failure to adhere to this rule can lead to collision due to further movement of the aircraft or due to the effects of jet blast

On-Gate Occurrences

On-gate collisions most commonly involve the parked aircraft being struck by support equipment but could also be caused by other aircraft manoeuvring or under tow. Whilst being struck by another aircraft is generally obvious to all parties concerned, accidents involving support vehicles may go unnoticed or unreported. The aircraft damage resulting from collisions with ground vehicles or objects can be a significant safety risk if not identified and remedied prior to flight. It is therefore critical that all accidents are reported and that the Flight Crew Pre Flight External Check includes a thorough visual inspection. Some of the more common occurrences include:

  • Aircraft struck by Passenger Boarding Bridge - a faulty bridge or an inadequately trained operator can result in the bridge striking the aircraft causing damage to the aircraft door(s) and/or fuselage
  • Aircraft struck by ground support equipment - below the wing services make use of a great deal of mechanised equipment such as belt loaders, forklifts, split-loaders, catering trucks and lav and water trucks. Faulty equipment, poorly trained operators, inattention or lack of appropriate marshalling can all lead to collision with the aircraft
  • Fuel truck damage - Damage from fuel trucks can occur in many ways such as improper or inappropriate positioning of the bowser, damage due to the hose lift platform striking the underside of the wing, improper hose coupling/decoupling, or from failure to detach hoses from the aircraft before moving the fuel truck
  • Non secured equipment - damage can be caused by improperly secured vehicles or support equipment, such as Unit Load Devices (ULD), being blown against the parked aircraft by the wind or by jet blast
  • Aircraft struck by other aircraft - other aircraft under tow or under their own power have the potential to strike a parked aircraft due to improper entry to adjacent gates, failure to follow taxi lanes, inattention or malfunction

Pushback Occurrences

Pushback occurrences are those which whilst the aircraft is being pushed off the gate and positioned in the taxi lane to either taxi under its own power or be towed to another location. The most common occurrences involve the pushback aircraft striking another aircraft, object or vehicle but that aircraft can also be struck by other aircraft or vehicles manoeuvring on the apron. Some of the more common occurrences include:

  • Use of inappropriate equipment - use of incorrect towbar or inappropriate tug can result in the aircraft being struck and damaged by the tug as it manoeuvres
  • Commencing pushback prior to retracting the Passenger Boarding Bridge - this can result in door and fuselage damage
  • Commencing pushback without clearance or in the wrong sequence - commencing push without clearance or not in accordance with the cleared sequence could result in collision
  • Pushing back without wing and tail "walkers" - the tug operator cannot adequately judge the wing and tail clearances of a large aircraft when conducting a pushback. Use of the appropriate number of guides is essential to prevent incident
  • Inappropriate engine power settings during pushback - whilst normal engine start during pushback is routine, actions, such as a cross-bleed start, which involve high power settings should not be undertaken until the push is complete. Doing otherwise could result in the tug operator losing directional control of the aircraft, shearing of the towbar safety pin and/or collision of the aircraft with the tug or other object
  • Simultaneous pushback from close or adjacent gates - gate proximity and configuration can result in loss of separation and possible collision of aircraft during concurrent pushback
  • Commencement of taxi before equipment is clear - In many cases, it is not possible to see the connected pushback equipment and crew from the flight deck. Crews must ensure that all equipment has been disconnected and moved to a safe location and that all personnel are clear prior to commencing taxi

Prevention

The great majority of collisions occurring whilst approaching, on, or leaving the gate are preventable. Robust training, appropriate and well promulgated procedures, consistent adherence to those procedures and a mature Safety Management System (SMS) all play a role in collision prevention. In particular flight and ground crew should:

  • ensure gate assignment is appropriate to the aircraft type
  • maintain the gate centerline whilst approaching and pushing off the gate
  • ensure that the gate safety areas are clear whilst the aircraft is approaching or departing the gate
  • be aware of wing and tail clearance at all times and using wing walkers when appropriate
  • make appropriate use of marshalling services both when the aircraft is approaching the gate and when vehicles are approaching the aircraft

Accidents and Incidents

  • A343, Frankfurt Germany, 2008 (On 21 August 2008, an Airbus A340-300 being operated by an undisclosed operator by a German-licensed flight crew on a scheduled passenger flight from Teheran to Frankfurt collided with a stationary bus with only the driver on board whilst approaching the allocated parking gate in normal daylight visibility. The No 4 engine impacted the bus roof as shown in the photograph below reproduced from the official report. None of the occupants of either the aircraft or the bus were injured.)
  • B74S, Stockholm Arlanda Sweden, 2006 (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”.)
  • 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.)
  • ATP, Jersey Channel Islands, 1998 (On 9 May 1998, a British Regional Airlines ATP was being pushed back for departure at Jersey in daylight whilst the engines were being started when an excessive engine power setting applied by the flight crew led to the failure of the towbar connection and then to one of the aircraft's carbon fibre propellers striking the tug. A non standard emergency evacuation followed. All aircraft occupants and ground crew were uninjured.)
  • B742, Stockholm Arlanda Sweden, 2007 (On 25 June 2007, a Boeing 747-200F being operated by Cathay Pacific on a scheduled cargo flight from Stockholm to Dubai had completed push back for departure in normal daylight visibility and the parking brakes had been set. The tow vehicle crew had disconnected the tow bar but before they and their vehicle had cleared the vicinity of the aircraft, it began to taxi and collided with the vehicle. The flight crew were unaware of this and continued taxiing for about 150 metres until the flight engineer noticed that the indications from one if the engines were abnormal and the aircraft was taxied back to the gate. The tow vehicle crew and the dispatcher had been able to run clear and were not injured physically injured although all three were identified as suffering minor injury (shock). The aircraft was “substantially damaged” and the tow vehicle was “damaged”.)
  • MD82 / MD11, Anchorage AK USA, 2002 (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.)
  • B772 / A321, London Heathrow UK, 2007 (On 27 July 2007, a British Airways Boeing 777-200ER collided, during pushback, with a stationary Airbus A321-200. The A321 was awaiting activation of the electronic Stand Entry Guidance (SEG) and expecting entry to its designated gate.)
  • 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.)
  • 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.)

Related Articles

Further Reading