What happened
On 27 September 2017, an Airbus A320, registration EC-LVQ, was being moved from parking Stand 318R at Dublin Airport in preparation for a flight to Madrid. The ground handling operation involved an initial pushback followed by a pull-forward maneuver using a tractor and towbar to align the aircraft with Apron Taxiway 5.
During this process, the flight crew began starting the aircraft's starboard engine. As the tractor turned to align the aircraft with the taxiway, the nose of the aircraft began to overtake the tractor, a phenomenon known as jack-knifing. The headset operator immediately directed the crew to shut down the engine to mitigate danger. Despite the driver's attempts to stop, the aircraft continued moving forward, eventually coming to rest with the tractor wedged against the starboard engine cowling. The incident resulted in substantial damage to the engine cowling, though there were no injuries to the 179 passengers or 6 crew members on board.
The investigation
The AAIU examined the mechanical state of the towing equipment and the procedures followed by the ground handling crew. Investigators found that the shear-pin in the towbar head had failed. While the tractor and towbar were appropriate for an Airbus A320, the investigation noted that the aircraft was not following the specific maneuvering lines designated for Stand 318R.
Engine data revealed that the starboard engine was in the middle of a start sequence, reaching approximately 54.9% N2 and 16.5% N1 before the process was aborted. Although the thrust produced was below idle levels, the ground handling company's manual explicitly prohibits engine starts during towing maneuvers. The investigation also noted that the ramp surface was wet and featured a slight 1% downhill slope.
Findings
- The primary cause of the incident was the failure of the towbar shear-pin during the pull-forward maneuver.
- The aircraft was not following the prescribed maneuvering path for its specific stand.
- The ground handling company's procedures, which prohibit engine starts during towing, were not followed.
- The wet ramp surface and the slight downhill gradient contributed to the severity of the collision once the tractor lost directional control.
- The thrust from the engine being started, while not causing the pin to fail, likely exacerbated the movement once the connection was lost.
Safety action
Following the incident, the ground handling company issued a safety notice to all staff, reinforcing the prohibition of engine starts during pull-forward or towing operations. Additionally, a safety recommendation was made to ensure all ground crews strictly adhere to the correct maneuvering procedures at Dublin Airport.