What happened
On 26 March 2017, an Airbus A320-214, registration G-EZTM, was parked at Stand 559 at London Gatwick Airport. The aircraft was undergoing maintenance to address a brake system indication fault. As part of the required maintenance task, the parking brake was set to the off position. Following the completion of this task, the parking brake was not re-engaged.
Prior to the maintenance work, the flight crew had performed their cockpit preparation checks and recorded the parking brake as being on. Consequently, the crew was unaware that the brake had been released during the subsequent maintenance activity.
During pre-departure preparations, ground handling personnel connected a tug to the aircraft. While the forward steps were still positioned against the aircraft, the ground staff removed the chocks. The tug driver then discovered that the tug's radio was non-functional and disconnected the vehicle to swap it for a working unit. During this disconnection, without communication to the flight crew, the aircraft began to roll backwards. The movement continued until the aircraft struck the boarding steps, resulting in damage to the fuselage and Door 1L. The crew applied the footbrakes to stop the movement. There were no injuries to the 161 passengers or 7 crew members on board.
The investigation
The investigation established that the aircraft's movement was possible because the parking brake had been left off following the maintenance procedure. Furthermore, the investigation found that the ground staff had removed the chocks while ground equipment was still in contact with the aircraft, which was a breach of the operator's established safety procedures.
Findings
- The maintenance task performed on the brake system required the parking brake to be released but did not include a step to re-apply it.
- The flight crew's pre-flight checks were completed before the maintenance task, meaning they believed the parking brake was engaged.
- The removal of chocks before all ground equipment was clear of the aircraft allowed the aircraft to move once the tug was disconnected.
- A lack of communication occurred between the ground handling staff and the flight crew during the equipment changeover.
Safety action
- The operator's engineering department is reviewing the relevant maintenance manual task and intends to suggest amendments to the aircraft manufacturer.
- The ground handling company has implemented staff retraining regarding chocking procedures and has reissued procedures for managing defective equipment.