What happened
On 21 August 2024, a Boeing 737-8AS, registration 9H-QAA, was undergoing a long pushback at London Stansted Airport. The aircraft, operated for a commercial passenger flight to Venice, was being moved from Stand 63R to a remote hold area on Apron Delta. The pushback was being conducted by a trainee driver under the supervision of a driving instructor.
During the maneuver, the tug instructor took over the controls from the trainee. While the instructor was focused on providing instruction and guidance to the trainee, the tug continued moving past the 'Tug release point' (TRP) ground markings. The aircraft eventually struck a blast fence located at the end of the taxiway cul-de-sac. The impact caused substantial damage to the aircraft's tail cone, tail fuselage, and the Auxiliary Power Unit (APU), which was running at the time of the collision. There were no fatalities and no injuries among the 6 crew members or 181 passengers on board.
The investigation
The AAIB investigation examined the actions of the ground crew, including the headset operator and wingman, as well as the visibility of the airport's ground markings. The investigation established that the tug instructor was preoccupied with training the trainee driver, which diverted his attention from the taxiway centerline and the TRP.
Investigators also noted that the ground crew members experienced a level of surprise as the aircraft moved past the intended stopping point. The wingman, who was not using marshalling wands, and the headset operator both observed the movement but did not intervene before the collision occurred. The investigation also looked into the visibility of the TRP, which was described as small and partially obscured by the aircraft's fuselage.
Findings
- The tug instructor failed to stop the aircraft at the TRP because he was prioritizing training the trainee driver over monitoring the aircraft's position.
- The TRP markings were not sufficiently prominent and were difficult to see from the tug's perspective.
- The ground crew members did not provide timely warnings or signals to stop the tug before the impact.
- The tug's engine was at idle power, and because the aircraft's main engines had not yet been started, there was no opposing thrust to assist in stopping the momentum once the TRA was exceeded.
Safety action
Following the incident, the airport operator increased the size of the tug release point markings from 0.5 m to 1 m and painted them on both sides of the taxiway centerline to improve visibility. Additionally, the ground handling agency issued a training reminder to all staff regarding the importance of adhering to TRP procedures.