What happened
On 31 March 2016, an Airbus A330-323, registered 9M-MTB, was undergoing pre-flight preparations at Melbourne Airport for a flight to Kuala Lumpur. The incident began when the captain engaged the aircraft's park brake to perform an external inspection. During this process, an aircraft maintenance engineer observed the park brake indicator light on the nose gear, leading them to believe the aircraft was secure.
Believing the brakes were firmly set, the engineer removed the main landing gear chocks. Shortly thereafter, the nose gear chocks were also removed to allow a towbarless tractor to dock with the aircraft. Unaware that the main gear chocks had been removed, the captain returned to the flight deck and released the park brake. Without the secondary security of the chocks, the aircraft began to roll backward approximately 3 meters, eventually striking the aerobridge. The impact caused damage to the aircraft's forward-left door, hinges, and the aerobridge itself. There were no injuries reported.
The investigation
The investigation focused on the lack of coordination between the flight crew, the engineering team, and the tractor operator. It was established that the maintenance engineer removed the main gear chocks out of sequence and without notifying the rest of the ground crew. Furthermore, the tractor operator's local practices at Melbourne Airport had omitted the specific step of verifying that main gear chocks were in place before docking.
Findings
- The primary cause was the uncoordinated release of the park brake while the main landing gear chocks had been removed.
- The maintenance engineer removed the main gear chocks prematurely and out of sequence with standard procedures.
- Ground crews failed to verify the presence of main gear chocks before the nose gear chocks were removed for tractor docking.
- There was a lack of explicit communication between the flight crew, engineers, and the tractor driver regarding the status of the aircraft's brakes and chocks.
- Local operational variations at the airport had led to the omission of critical safety checks in the tractor operator's routine.