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”.
An Investigation was carried out by the Swedish Accident Investigation Board. It established that the aircraft, with the First Officer as PF and in full control, had begun to taxi in a right hand turn before an ‘all-clear’ signal had been given by the supervising dispatcher to indicate that the ground crew and their vehicle were clear. It was noted that, at the time the taxi was commenced, the disconnected tow vehicle was not yet far enough away from the aircraft for it to be readily visible from the flight deck. The diagram below taken from the official report shows the tow vehicle as it was positioned in yellow and the approximate area ahead of the aircraft which would have been invisible to the occupants of the flight deck in their normal positions in red – the forward end of this red triangle was identified as being about 25 metres ahead of the nose landing gear.
Sketch of a visual field of a B742, Source:Report RL 2008:06e
It was established during the subsequent crew interviews that, at the time of the collision, the flight crew had been aware of a “light thud and a juddering” during the sharp right hand turn which had been made as taxi commenced but had attributed this to the nose gear skidding on the ground during such a tight turn.
The Investigation noted that the three flight crew involved, the two pilots and a flight engineer (F/E), were based in Germany and England and had arrived at Arlanda as passengers shortly before the accident flight having been awake for 18-20 hours (although not on duty for all of this time). It was therefore considered that fatigue may have played a part in the failure of the crew to obtain an all-clear signal before beginning to taxi. It was noted that the flight crew after start checklist did not contain any reference to the receipt of an ‘all-clear’ signal but that a note in the corresponding Expanded Checklist contained in the aircraft Operations Manual stated that “under no circumstances should parking brakes be released until (the ground crew visual all clear signal) has been given” and “the PNF has confirmed clear on his side of the aircraft”.
Separately from the potential contribution of fatigue, it was noted by the Investigators that taxi had commenced sooner than it was likely that the tow vehicle could have been removed and that the failure of all three flight crew to recognise that the full supporting actions for completion of the after start checklist had not been taken indicated poor Crew Resource Management .
It was established by the Investigation that the procedures to which the tow vehicle crew were working did not contain any reference to the distance which the tow vehicle should be initially moved from the aircraft after tow bar disconnection and that it would have been useful for the field of view from the aircraft to have been considered in this respect.
The fact that a fuel leak from the aircraft caused by the accident had not been attended by the airport RFFS until nearly an hour after the accident was also noted.
The Investigation concluded that the cause of the accident was:
“inadequate checklists for the pilots in respect of checking that an all clear signal had been received”.
It was also considered that:
“a probable contribution was that stress and fatigue factors limited the concentration abilities of the pilots”.
The Final Report of the Investigation was published on 6 October 2008 and may be seen in full at SKYbrary bookshelf: AIB Sweden Report RL 2008:06e
Two Safety Recommendations were made as a result of the Investigation:
- That the Swedish Civil Aviation Authority ensures that the fire safety regulations for Stockholm/Arlanda and other relevant Swedish airports are revised so that collisions involving aircraft are assigned a sufficiently high risk assessment. (RL 2008:06 R1)
- That the Swedish Civil Aviation Authority ensures that the operating manuals for air traffic control at Stockholm/Arlanda and other relevant Swedish airports are revised so that collisions at the airport involving aircraft are a criterion for raising the alarm with the rescue services. (RL 2008:06 R2)