Canada B773 at Paris on Jul 24th 2019, ground agent injured by tow bar
Last Update: April 14, 2021 / 10:35:59 GMT/Zulu time
On Apr 14th 2021 the BEA released their final report concluding the probable causes of the accident were:
The following factors may have contributed to the accident:
- A misunderstanding between the tractor driving crew and the headset operator. The lack of a briefing may have resulted in this misunderstanding that was also between the personnel of two separate companies. The headset operator is expected to initiate procedures in the event of an anomaly during the push-back operation. As this agent was unaware of any anomaly, the immediate application of these procedures, including the request to apply the aeroplane parking brake, may have been compromised.
- The lack of implementation of a block on the nose gear. The investigation showed that the positioning of a block depends on the air operator’s procedures and is not systematic.
- The headset operator’s late action in asking the crew to apply the aeroplane parking brake as soon as he saw the driver’s instructor initiate removal of the tow bar, despite this surprising him and him not fully understanding the reason for this action at this time.
- The failure of the driver’s instructor to check the signal light on the landing gear equipping this type of aeroplane before initiating the tow bar removal operation.
The BEA reported that the tow truck (tractor) was operated by two ground agents, the driver being a trainee completing his training and being under supervision by a tow instructor. In addition, there was a head set operator from a different company talking to the flight crew.
The BEA summarized the flight crew statement:
The crew explained that, during the push-back manoeuvre, the tractor was positioned perpendicularly to the aeroplane’s centreline. They added that they had heard a noise that they identified to be a rupture of the tow bar shear pin.
The crew then saw the driver and the instructor have a brief discussion and the instructor alight the tractor. With the tractor no longer in sight, the aeroplane moved forward and the crew stated that they immediately applied the parking brake. As they did so, they received the request to apply the parking brake from the headset operator.
The BEA summarized the statements of the tow instructor:
The instructor had been employed by AGS since 2001. He is the only driver instructor and started the second and final week of the driver’s practical training which involved asking him to perform push-backs on the most difficult parking areas, including A38 due to its proximity to a grass strip.
On the day of the accident, this was the eighth and last push-back of the day. He stated that he and the driver had arrived approximately 20 minutes before the scheduled block time. The instructor showed the trainee the type of tractor and the type of tow bar to be used.
At the start of the push-back, the driver made a turn that was too wide and had some difficulties following the ground markings. At the end of the push-back, he managed to align the main landing gear on either side of the taxiway centreline. However, the nose gear was still approximately 80 cm from the centreline and the driver performed a final manoeuvre to align the nose gear. During this manoeuvre, the turn angle between the bar and the tractor reached the maximum turn limit and a shear pin ruptured.
The instructor then alerted the headset operator using a hand signal and indicated for him to look towards the shear pin to notify him. Convinced that the headset operator had understood, he thought that the latter had therefore informed the crew and asked them to apply the aeroplane’s parking brake. He then told the trainee to apply the tractor parking brake then alighted the tractor. He specified that the nose gear of the Boeing 777 is equipped with a light signalling application of the parking brake. He added that he had not checked whether this light was on before initiating the operations to disconnect the tow bar from the tractor. He firstly lowered the retractable wheel gear of the tow bar then asked the driver to raise the drawbar pin to disconnect the tow bar from the tractor.
After this action, the aeroplane began to move forwards and to exert a force on the tow bar. The wheel gear then trapped his right leg and he fell over. The tow bar then suddenly disengaged and hit his right leg.
The instructor explained that blocks are very rarely used. He added that he had not felt particularly stressed on the day of the accident as the aeroplane was on time. He had not felt particularly tired.
The BEA summarized the testimony of tractor driver (trainee):
Having worked as a ramp agent at AGS for a year and a half, he was completing his second week of training to become a tractor driver. This was the first time he had encountered a situation involving rupture of the tow bar shear pin. He stated that for the push-back operation, he had been at the wheel of the tractor and accompanied by his instructor. A third person, in direct communication by headset with the aeroplane crew was standing near the nose gear.
He specified that no briefing had taken place between them and the headset operator prior to the push-back operation. At the end of the push-back, now in the position in which the tow bar should be removed, the instructor alighted the tractor. The driver applied the tractor parking brake. He could not remember if he had made the signal to ask the headset operator to ask the crew to apply the aeroplane parking brake. He added nevertheless that he had systematically done this on other occasions. He remained in the driver’s seat of the tractor throughout the operation. At the request of his instructor, he raised the drawbar pin to release the tow bar. He saw the aeroplane move forwards and the tow bar subjected to force then hit the leg of the instructor.
He was convinced that the headset operator had understood the situation and asked the crew on board the aeroplane to apply the parking brake. He added that the use of a block in addition is not systematic and that, to his knowledge, only one operator makes this mandatory in its procedures.
The BEA summarized the testimony of the head set operator:
On the day of the accident, the headset operator arrived at the parking area and positioned himself without conducting a briefing with the driver of the tractor and his instructor.
From the start of the push-back, he noticed that the driver had turned too widely. He stated that this had been rectified towards the end of the operation. During the final manoeuvre, he saw that the tractor was at maximum turn angle. He did not identify the rupture of the nose pin but observed that neither the tow bar nor the tractor were aligned. He did not see the driver or the instructor make a hand signal to indicate the stop and request for application of the aeroplane parking brake. He saw the instructor alight the tractor that was still moving and approach the tow bar and thought that he was going to disconnect the bar to enable the tractor to make a manoeuvre to improve its alignment. He then saw the aeroplane move forwards and the tractor move backwards. According to him, it was at this time that the shear pin ruptured and he immediately asked the crew to apply the parking brake.
The BEA stated that even surveillance videos available made not possible to see the last moments of the occurrence and thus summarized the scenario:
The statements collected differ in such a way that the investigation was unable to determine the exact sequence of the accident, in particular:
- the exact time of the shear pin rupture;
- whether signals were exchanged between the headset operator and the agents on board the tractor.
The fact is that the driver’s instructor alighted and started to remove the tow bar without the aeroplane parking brake being applied and without blocks in position. During disconnection of the bar, a forward movement of the aeroplane led to the immobilisation of the agent, his foot trapped under a tow bar wheel. This agent was then struck by the tow bar after it was released.
This article is published under license from Avherald.com. © of text by Avherald.com.
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