|Title:||Runaway Learjet 45, D-CNIK, Gatwick, March 17, 2006|
|Micro summary:||This parked Learjet 45 swung out of control when the thrust of an operating engine was advanced.|
|Event Time:||2006-03-17 at 2029 UTC|
|Publishing Agency:||Aircraft Accident Investigation Board (AAIB)|
|Publishing Country:||United Kingdom|
|Site of event:||London Gatwick Airport|
|Departure:||London Gatwick Airport, West Sussex, England, United Kingdom|
|Airplane Type(s):||Learjet 45|
|Type of flight:||Corporate|
|Executive Summary:||The aircraft was being prepared for departure to Paris. The commander was at the rear of the cabin and the co-pilot was on the flight deck. The right engine was running in order to provide electrical services and air conditioning for the cabin. The engine power was inadvertently increased to 70% N1 and the aircraft moved forwards, unobserved by the co-pilot. Whilst moving forwards through the cabin, the commander fell from the open doorway. The outer part of the left wing struck a parked motor vehicle and the aircraft swung rapidly to the left, turning through 180º before coming to rest again against the side of the vehicle. The commander and a ramp handling agent were both struck by the aircraft and knocked to the ground. The commander was seriously injured.|
The evidence derived from the recorded data was that the aircraft had moved on the stand as a result of a forward movement of the right (No 2) engine thrust lever which led to a corresponding increase in the right engine power. The chocks were pushed out of the way as the aircraft moved forward. The left wing contacted the parked vehicle and the aircraft started to pivot around it to the left. The direction and rate of turn thereafter was affected by a number of factors which were additive: the restraint on the left wing, the high power on the right engine and the absence of nose wheel steering which allowed the nosewheel to casterfreely. The wind which was strong and gusty would also have acted in the direction of the turn.
On his arrival at the aircraft the co-pilot had checked that chocks were in place; they were positioned at the nosewheel. The chocks used were those carried with the aircraft; they were made of wood and of relatively light weight. These chocks could easily be pushed aside were any force applied and would not have been sufficient to hold the aircraft against any significant power. The fact that the chocks were in position may have given the co-pilot a false impression that the aircraft was secure against movement.
This particular model of the Learjet 45 did not have an APU which meant that in order to supply air to the cabin and to regulate the temperature, an engine needed to be running. It was normal practice, therefore, to start the right engine to supply bleed air to the cabin whilst preparing for a flight.
The co-pilot reported that his first action on boarding the aircraft was to put on the park brake. The park brake position is not one of the parameters recorded on the FDR so whether or not the action was carried out could not be definitely determined. For the aircraft to have moved, there were three possibilities. Firstly, the park brake was not effective because the handle was never set; secondly the handle was set but there was insufficient pressure in the accumulator to apply the brakes at the wheels; and thirdly, the brakes could have been applied but overcome by the additional thrust when the thrust lever was advanced. It was not possible to determine which of these occurred but it was noted that unless the correct procedure was used to set the brake then it was possible to set the handle without actually applying the brakes. The procedure in the AFM required the accumulator to be charged by activating the aux hyd pump before applying the park brake. However this action was not carried out and the co-pilot seemed to be unaware that it was a required procedure. Nevertheless, if sufficient residual pressure had been retained in the system, the brakes would have been applied.
The co-pilot stated that he had been in his seat to start the engine. There were a number of activities that may have distracted him and caused him to move from his seated position afterwards. There was no specific requirement in the Operations Manual which required a pilot to be seated at the controls while an engine was running. It seems likely that as he moved around, he inadvertently moved the right thrust lever forward, either directly through physical contact or indirectly through snagging with clothing or equipment. At first he did not notice that the aircraft was moving and when he did, he was not in a position from where he could immediately apply the brakes. The movement cues could have been reduced by the lack of external visual cues in the dark and, if his attention was focused elsewhere, he would not necessarily have noticed the movement.
In an aircraft such as this, where it is necessary to run an engine to supply ground services, it may be that there is insufficient awareness amongst flight crew of the associated hazards. It is also possible that ground personnel working around the aircraft are less aware and therefore less cautious than when engines are started for flight. It is likely that a general practice had developed within the operation whereby one engine was started as a routine without reference to a checklist procedure. If the co-pilot’s actions were not in accordance with the general practice then this should have become apparent during his training.
The operator’s checklist did not specifically require the co-pilot to set the park brake. Although the AFM did provide a procedure to set the park brake, it was part of the ‘Before Starting Engines’ checklist. This checklist was lengthy and not necessarily appropriate for starting one engine just to supply ground services as in this case. Failure to use a checklist in such circumstances is made more likely by the absence of an appropriate abbreviated procedure. Conversely, when the enginesare started for the purpose of flight, more formal attention would probably be given to the required procedures and awareness levels would be raised.
|Learning Keywords:||Operations - Crew Resource Management|
|Operations - Ground Collision|
|Operations - Task Saturation|
|Consequence - Damage - Airframe or fuselage|
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