What happened
On 23 March 2019, an Airbus A320-232, registration HA-LPL, was preparing for departure at Stand 2 of Bristol Airport. During the pushback preparation, a TLD 200MT towbarless tug was being used to position the aircraft. The tug was operated by a driver undergoing training for this specific model, accompanied by a qualified trainer.
As the tug's hydraulic paddles were closing around the nosewheels, the trainer heard a loud bang and felt a significant vibration through the aircraft's nose gear. The tug driver immediately halted the procedure and applied the brakes. Upon inspection, the crew discovered that the left-side paddle had struck and damaged the nut on the torque link centre pivot of the nose landing gear. There were also visible marks on the tug's paddle. The incident resulted in no injuries to the 159 passengers or 6 crew members, but the aircraft was removed from service for repairs.
The investigation
The AAIB investigation focused on the alignment of the tug and the mechanics of the impact. It was established that the tug's laser guidance system had been aligned with the main forging of the nose gear leg rather than the nosewheels themselves. At the time, the nosewheels were positioned 10° to 15° off-centre.
While the tug's automated system prevents errors if the wrong aircraft type is selected, it cannot detect if the operator has aligned the system to the gear leg instead of the wheels. The investigation found that the hydraulic force of the closing paddles caused the edge of the torque link nut to fail, allowing the paddle to slip past with a sudden jolt.
Findings
- The primary cause of the damage was the incorrect alignment of the tug's laser guidance system with the nosewheels.
- The driver and trainer were using a laser system that was focused on the nose gear main forging while the wheels were offset by 10° to 15°.
- A momentary lapse in concentration likely led to the alignment error, which went unnoticed because the degree of wheel offset was not visually significant.
- The tug's automated software does not provide a warning if the operator aligns the system to the gear leg rather than the wheels, provided the correct aircraft model is selected.
Safety action
- The handling company reviewed its towbarless tug training to emphasize the necessity of aligning with the nosewheels.
- Pushback crews have been instructed to brief aircraft crews on the importance of keeping nosewheels straight when possible.
- The handling company is working with the tug manufacturer to explore a warning system for wheel misalignment.
- For the Airbus A320 series, the handling company will use conventional tow bars or the TLD 100E tug whenever possible to avoid the risks associated with the TLD 200MT.