What happened
On the day of the event, a DC-9-32 was parked at the gate with an inoperative APU. Due to snow and ice covering the ramp, the captain determined that a single engine cross bleed start would require the operative engine to reach approximately 80% N1. Consequently, the crew elected to start both engines while still at the gate before proceeding with pushback.
During the pushback maneuver, as the tug driver attempted to push the nose of the aircraft toward the west, the airplane encountered icy conditions and moved forward, striking the tug. At the moment the aircraft lost traction, the tug was positioned nearly 90 degrees to the right side of the aircraft nose. The tug driver observed the forward movement and stopped the vehicle; however, because he was not wearing a headset, he was unable to notify the cockpit crew of the incident.
The investigation
The investigation revealed that the tug driver did not wear a headset because the headset cord had been broken and repaired multiple times and was too short to reach his position. Instead, a walker positioned near the nose of the aircraft was wearing the headset. This walker reported looking away at the time of the movement and did not observe the aircraft moving forward in time to alert the cockpit.
Findings
- The pushback was performed by a contract crew trained according to the airline's Ground Maintenance Manual (GMM).
- The GMM lacked specific instructions regarding procedures for performing pushbacks on icy surfaces.
- Communication failure occurred because the tug driver was not connected to the cockpit crew via headset.