What happened
On 17 February 2008, an Airbus A3CO211, registration G-DHJH, was undergoing a pushback maneuver at Manchester Airport. During the process, the cockpit crew heard increasing 'clonking' noises originating from the nose landing gear area. This sequence of sounds culminated in a loud bang, at which point the pushback operation ceased. The crew observed that the towbarless tug was positioned at an acute angle to the aircraft. The tug crew notified the flight crew that significant damage had been sustained and requested an engineering inspection. There were no fatalities and no injuries to the 220 passengers or 7 crew members on board.
The investigation
Investigators established that the aircraft's nosewheels had become disengaged from the tug's hydraulic 'grab and retention' mechanism. As the wheels lost their connection to the tug, they made contact with the apron surface. This contact resulted in damage to both nosewheel steering motors mounted on the landing gear leg, necessitating a complete replacement of the nose landing gear.
Prior to the pushback, maintenance had been performed on the aircraft to replace one of the two nose landing gear wheels. While the tyres were inflated to the correct pressure, the engineer deflated them to allow the tug to separate from the aircraft without checking the pressures afterward.
An examination of the specific towbarless tug used in the incident revealed no mechanical faults, and the issue could not be replicated during subsequent testing. However, airport authorities noted that this particular tug had been involved in four previous nosewheel damage events involving different operators.
Findings
- The nosewheels disengaged from the hydraulic-powered retention mechanism of the towbarless tug.
- The disengaged wheels made contact with the ground, causing damage to the steering motors.
- The towbarless tug lacked a positive mechanical locking or safety feature to prevent the tyres from contacting the ground during maneuvering, a feature present on other manufacturers' equipment.
- The tug had a history of similar nosewheel damage incidents.