ATP, Jersey Channel Islands, 1998
From SKYbrary Wiki
|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.|
|Actual or Potential
|Ground Operations, Human Factors|
|Flight Conditions||On Ground - Normal Visibility|
|Aircraft||BRITISH AEROSPACE ATP|
|Operator||British Regional Airlines|
|Type of Flight||Public Transport (Passenger)|
|Take off Commenced||No|
|Location - Airport|
|Tag(s)||Flight Crew / Ground Crew Co-operation,|
Inappropriate crew response - skills deficiency,
Procedural non compliance
|Tag(s)||Aircraft / Vehicle conflict,|
Aircraft Push Back
|Damage or injury||No|
|Causal Factor Group(s)|
On 9 May 1998, a BAe ATP being operated by British Regional Airlines on a domestic scheduled passenger flight from Jersey was being pushed back off the gate on departure in normal daylight visibility. The second engine had just stabilised after start and the aircraft had been aligned with the taxiway centreline when the aircraft began to push the tug, the tow bar failed and the aircraft rolled forward and the right hand propeller struck the tug cab. About 90 seconds after the impact, the flight crew noticed a small amount of what was identified as smoke in the flight deck and an emergency evacuation was ordered using the integral air stairs at Door 1L and the emergency slide at Door 2L.
An Investigation was carried out by the UK AAIB. It was noted that a three man pushback crew had been used and that only the safety of the tug driver had been in question as the aircraft right hand six-bladed propeller struck the tug cab. The tug driver reported that he had felt the front of the tug lift, which caused him to lose the ability to steer it and the aircraft then seemed to push forward, the tug jack-knifed and the aircraft moved towards the tug and the right propeller. The driver did not remember how he escaped from the vehicle and, although physically uninjured, later stated that he was suffering from post-traumatic stress.
Flight Data Recorder (FDR) data indicated that the No 2 engine had stabilised at 15% torque after start and remained at that level until the impact with the tug. The No 1 engine stabilised at 10% after start and remained at that level until it was shutdown after the impact. Normally the torque is set at 7 to 8% after start by positioning the engine power levers to the marked ‘Minimum Torque’ position and checking that it has been achieved.. The three previous engines starts earlier in the day by this crew were all found to have been accompanied by excessive torque settings, in contrast with the flights by the aircraft the previous day with a different crew where all post-start torques corresponded to the required minimum torque position. Several witnesses to the pushback had commented that engine noise seemed much higher than usual.
The investigation established that post-event physical evidence “confirmed eye witness reports that jack-knifing had occurred, with the aircraft rotating the tug to the right until the tow bar lay along the front bumper, at right angles to the tug. The tow bar eye end was therefore overstressed in bending rather than tension or compression. In this condition the shear pin was not loaded. The leverage produced by this configuration caused the tow bar weld to fail after a small number of high stress cycles, leaving the aircraft free to accelerate past the tug, striking it with the No 2 engine and propeller.”
The Investigation concluded that “The balance of evidence indicates that the engines were at a higher torque than normal and that this was the initiating event in the accident. The reason why the crew had set, and more importantly not noticed, the higher than normal torque after all four starts that day could not been satisfactorily explained.”
It was noted that 9 days after the Accident, the Aircraft Operator had introduced a change to SOPs involving the immediate cessation of all engime starting during pushback on the aircraft type involved. Flight crews had also been formally reminded that they should check that indicated engine torque was at minimum after each engine start and that full attention should be given to the ground crew leader thoughout a push back whilst also maintaining full awareness of activity around the aircraft.
The Final Report of the Investigation was published on 4 March 1999 and may be seen in full at SKYbrary bookshelf: AAIB Bulletin No: 3/99 Ref: EW/C98/5/3 Category: 1.1
One Safety Recommendation was made in the Report:
“It is recommended that Jersey Authorities require the ground handling organisations at Jersey International Airport to review the characteristics of their aircraft towing tugs to ensure that there is a sufficient safety factor available when used for push back operations with the aircraft attached to the front towing pintle.” (99-8)