What happened
While taxiing toward the runway for departure, the crew observed the APU door light illuminate. In response, the airplane returned to the loading dock, where the engines were shut down and the APU door was closed and secured. Following this procedure, the engines were restarted, and a second pushback attempt was initiated.
During this second pushback, one maintenance technician was positioned on the right side of the aircraft wearing a headset, while another technician operated the tug. After receiving clearance to push, the tug driver executed a gradual turn intended to avoid equipment and minimize jet blast near other gates. However, halfway down the ramp, the Cessna (type not specified) contacted the loading dock, resulting in an 8-foot gash along the left side of the aircraft below the cockpit area. No injuries were reported.
The investigation
The tug operator reported that the tug's drive mechanism was sticking in a '2-wheel' or 'crab' mode during the maneuver. A post-accident investigation of the tug found no mechanical discrepancies, and testing of removed components revealed no anomalies. Despite this, other technicians later reported experiencing the same intermittent issue. Following the replacement of these components, the tug functioned without further problems. A representative from the tug manufacturer noted that the operator would have maintained front wheel steering and braking capabilities regardless of the system status.