Event Description
On 21 December 2015, an Airbus A320 aircraft was being prepared for pushback at Katowice-Pyrzowice Airport (EPKT). The flight coordinator, positioned near the aircraft and maintaining communication with the captain via headset, had readied the aircraft for the procedure. A Goldhofer AST 3 tug arrived to perform the pushback. As the tug approached, the operator noted that the aircraft's nose wheels were slightly turned and made several corrections to align the tug. After positioning, the operator observed an axial offset of 3 to 4 centimeters to the left relative to the nose gear. Despite this, the operator considered the alignment acceptable for safe attachment.
During the lifting process, the nose wheels straightened upon contact with the tug's lower grabber, causing the wheels to shift right. This resulted in direct contact between the grabber components and the nose gear nut, damaging it. After lifting, the operator noticed that the right grabber was positioned too deeply toward the gear leg. Concerned, the operator exited the tug and asked the flight coordinator to inspect the attachment. The coordinator observed that the right grabber protruded beyond the wheel outline and was too close to the gear leg, and also noted contact between a scissor-system element on the No. 1 engine side and the right grabber's rollers. However, the coordinator was simultaneously engaged in radio communication with the captain, verifying taxiway availability, starting engine No. 2, and disconnecting the ground power unit (GPU). Standing about one meter from the tug, at an oblique angle to the gear leg, the coordinator did not directly observe the final closing of the grabber mechanism.
Investigation Findings
The investigation determined that the tug operator held current certifications, but his practical training had only been conducted on an AM210 tug, not on the Goldhofer AST 3 involved in the incident. The operator reported feeling stressed and uncertain during the procedure due to lack of practice on that tug type. Approximately three weeks earlier, he had refused to push back an aircraft using the Goldhofer AST 3 due to inexperience, prompting a refresher training that was limited to instruction and control-panel familiarization. The practical training process was found inadequate as the operator received pushback authorization without having practiced on all tug types in use.
Additionally, the tug operator failed to follow applicable procedures. The flight coordinator, also current on training, did not properly supervise the tug attachment process due to multitasking and was positioned where he could not adequately observe the approach and clamp closure. The parking stand was found to have insufficient lighting, which was identified as a contributing factor.
Probable Causes and Contributing Factors
The investigation identified three direct causes: 1. Inadequate practical training process for the tug operator. 2. Non-compliance with applicable procedures by the tug operator. 3. Non-compliance with applicable procedures by the flight coordinator.
A contributing factor was insufficient lighting of the parking stand.
Preventive Actions Taken
The user's committee (handling agent) implemented the following measures:
- The tug operator was sent for renewed practical training on each tug type in use, and was removed from pushback and towing duties until passing an exam.
- The incident was discussed with ground equipment operators and flight coordinators.
- The committee proposed considering changes to training processes, procedures, and verification of tug operators due to training gaps.