What happened
On 12 May 2011, a Boeing 737-800, registration EI-DYM, was performing a scheduled passenger flight from Liverpool John Lennon Airport to Alicante. The flight was carrying 169 passengers and a crew of six. Following a standard pushback from Stand 8, the aircraft received taxi clearance and began moving toward Runway 27.
During the taxi, approximately 400 metres from the stand, the flight crew felt or heard an impact. Air Traffic Control subsequently contacted the aircraft to inform the crew that the plane may have struck a towbar. An inspection revealed that the towbar had become lodged against the aircraft's left main landing gear, causing damage to the landing gear assembly, the nosewheel tyre, and the ground towing equipment.
The investigation
The investigation examined the actions of the ground handling personnel and the equipment used during the pushback. It was determined that after the pushback was completed, the headset operator had signaled to the commander that the taxi route was clear. The ground crew then moved to the parking area.
Investigators found that the tug driver had noticed the towbar remaining in the aircraft's path after the pushback. He attempted to alert the flight crew, but the crew was unable to see him. The ground crew then notified Air Traffic Control. The investigation also looked into the functionality of the airport's radio communications, noting a recent system failure that had affected vehicle radios, though the tug driver was using a handheld unit with a weak signal.
Furthermore, the inspection of the towing equipment revealed that the towbar locking pin was not the original part and was improperly modified. The pin featured a broken handle and a square flange that prevented it from fully engaging the locking mechanism, meaning it could not reliably prevent the pin from lifting out of the bracket while the tug was in motion.
Findings
- The ground crew did not follow established procedures, which required the tug to be positioned forward of the aircraft to block the taxi path and prevent premature movement.
- The headset operator failed to confirm that the taxi route was clear from a position level with the wing tip, where the flight crew could see him.
- The towbar was left obstructing the aircraft's taxi route.
- The towbar locking pin was improperly fitted with a modified flange that failed to provide a secure mechanical lock.
- The tug driver's handheld radio signal was too weak to effectively communicate the hazard to the flight crew.