What happened
During a pushback sequence, a misunderstanding regarding the status of ground equipment led to a near collision. The flight crew interpreted the display of a bypass pin by the Aircraft Maintenance Engineer (AME) as a signal that all vehicles and personnel had cleared the aircraft and that it was safe to begin taxiing. Conversely, the ground crew operated under the expectation that the aircraft would remain stationary until all personnel and equipment had crossed the designated boundary of the S7 disconnect point.
Both the flight crew and the AME were waiting for Air Traffic Control (ATC) to confirm that the tug and AME were clear before providing taxi clearance. However, the aircraft began its taxi maneuver while the tug was still in the vicinity. This movement occurred before the tug had moved to a safe distance, creating a risk of impact.
The investigation
Investigators examined the conflicting expectations held by the various parties involved. It was determined that the flight crew and ground crew held differing understandings of the procedures governing the end of the pushback sequence. While flight crew procedures mandate a visual confirmation that all ground equipment is clear of the aircraft before taxiing, the first officer's assessment of the tug and tow bar's position was inaccurate. The investigation noted that the first officer's perception of the distance between the tug and the right engine may have been influenced by the expectation that the area was clear, following communications with the AME and ATC regarding taxi clearance.
Findings
- The primary cause of the incident was the differing understandings of procedures between the flight crew and the ground crew regarding when it was safe to commence taxi.
- The flight crew interpreted the AME's bypass pin indication as a notification that all equipment was clear.
- The ground crew expected the aircraft to wait until all personnel and equipment had crossed the S7 disconnect point boundary.
- The first officer incorrectly assessed the distance of the tug from the aircraft's right engine.