Aviation Safety Investigation Report - Final

The Australian Transport Safety Bureau did not conduct an on-scene investigation of this occurrence. The report presented below was prepared principally from information supplied to the Bureau.

REPORTED INFORMATION

At 1855 on 21 June 2004, a Boeing 717-200 aircraft, registered VH-VQB, was being prepared for departure at gate 49 at Sydney Airport. At the same time, another company Boeing 717-200 aircraft, registered VH-VQE, was being prepared for departure at the adjacent gate 53.

Both aircraft had been prepared for pushback and had remote control Power Push Units (PPU) positioned on the respective aircraft main landing gear. VQB was in the final stages of preparation for departure with all ground service equipment clear of the aircraft, all passengers on-board and seated with door 1 Left (L1) open and the aerobridge connected to the aircraft. The cabin service manager was completing documentation in the aircraft near door L1, and two customer service officers were located on the aerobridge.

VQE was ready for departure ahead of schedule and the flight crew received a pushback clearance. They then advised the ground crew that the aircraft was 'clear to push'. A push back was commenced by a ground crewmember, using a hand-held remote control unit, however the PPU did not respond to the ground crew's command to commence reversing. The ground crewmember, initially believing the remote control unit battery was discharged, replaced the battery and attempted a second pushback without success.

At the time the command to pushback was sent to the PPU attached to VQE at gate 53, VQB began to move rearwards at gate 49. The flight crew of VQB, sensing the unexpected movement, immediately applied the aircraft brakes; however the aircraft had moved rearward more than a metre. As the aircraft moved, the two customer service officers in the aerobridge became unsteady on their feet and a flight attendant in the aircraft galley received a minor scratch on one arm. Once the aircraft was stopped and secured, all passengers were disembarked through door 1 Right using portable stairs.

A subsequent examination of the aircraft revealed that VQB had been damaged as a result of contact between the aircraft and the aerobridge. The left angle of attack vane was bent, there was some minor skin damage around the angle of attack vane mounting and the L1 door trim was damaged. The damage was repaired and the aircraft was returned to service the following day.

Aircraft Ground Handling

Ground handling services for the aircraft operator were provided by a contracted ground handling agent. The agent owned and operated the PPUs and trained staff in their operation. The PPUs were attached to the aircraft main landing gear and provided motive force for aircraft pushback without the need for a towbar. The PPUs were activated via a hand-held remote control unit. The remote control units had an operating range of approximately 100 metres and were digitally encoded to ensure that the remote control unit would only operate its assigned PPU. The two PPUs and controllers used by the operator in Sydney were marked with matching serial numbers and two amber lights would illuminate on the PPU when any remote control button was pushed, signifying that the PPU was the one being activated.

At the time of the occurrence, the ground handling crews for gates 49 and 53 had inadvertently obtained the incorrect remote control units for their respective PPUs prior to the commencement of aircraft pushback.

As a result of this occurrence, the aircraft operator advised the ATSB that it had initiated a number of immediate safety initiatives to prevent a recurrence, including:

• Issuing a notice to all contracted ground handling staff requiring that the correct controller/PPU combination be cross checked by two staff members prior to push back operation commencing. It was intended that process would no longer be required once the long term actions have been implemented.
• A reassessment of all PPU operators was carried out by a manufacturer approved trainer. This training and assessment was documented in accordance with the contracted company procedures.
• Permission from the flight crew must be obtained prior to connecting PPUs to aircraft (in addition to asking for the park brake to be set). This is designed to reinforce the connection between connecting the PPU to the aircraft and the need for the park brake to be set.
• The engine of the PPUs is to be stopped after connection to the aircraft and started prior to push back using the remote control. This ensures that the first remote control command is not a commanding movement.
• Lockable boxes are to be installed on the PPUs to house the remote control units. The controllers remain with the PPU at all times.
• PPUs and controllers have been colour coded and large numbers placed on the PPUs to allow quick visual identification.
• The PPU manufacturer is to be asked to consider an engineering solution that prohibits the use of the incorrect remote control being used to inadvertently move an aircraft.
• The function of the remote control communication indicator lights is to be included in training syllabi and procedure documentation.
• The newly fitted test button on the remote control is utilized as a safeguard by requiring the operator to test the remote communication prior to beginning each push back operation.
• Consideration be given to requesting the manufacturer to change the control logic to require the test button to be used in the period shortly before the push or pull button action.