What happened
On the evening of December 2, 2004, an Airbus A320, registration HB-IJL, operating as Swiss International Air Lines flight SWR 1499, landed at Zurich Airport following a flight from Prague. After vacating runway 14, the crew was instructed to taxi via various taxiways toward runway 28. Simultaneously, a British Airways City Express BAe146-200, registration G-GNTZ, was taxiing toward the same runway for departure.
While the A320 was approaching runway 28, the aerodrome controller issued a clearance for the HB-IJL to cross runway 28. Almost immediately after this clearance, the controller issued a takeoff clearance to the G-GNTZ. The crew of the HB-IJL, remaining alert on the tower frequency, realized the conflict and performed an abrupt hard braking maneuver to stop the aircraft. The pilot of the A320 subsequently contacted the tower to confirm they had stopped off the runway, prompting the controller to order them to hold their position.
The investigation
SUST examined the coordination procedures used between the tower and departure controllers. The investigation found that the controller was distracted by an automated acoustic signal, "wait-cancelled," generated by the TACO electronic coordination system. This signal was triggered by the departure controller using a non-standard, manual coordination method to adjust departure intervals.
Furthermore, the investigation looked into the lighting configuration on the taxiway. At the time of the incident, the red stop bar lights had been deactivated and the green taxiway centerline lights were active. The crew of the HB-IJL had already passed the stop bar with the nose of the aircraft when the takeoff clearance was given to the G-GNTZ.
Findings
- The controller issued a takeoff clearance to the G-GNTZ while simultaneously having authorized the HB-IJL to cross the same runway.
- The controller's attention was diverted by a non-standard coordination procedure involving a "wait/wait-cancelled" signal.
- The use of this specific coordination method was not an official or instructed procedure and was prone to causing misunderstandable signals.
- The crew of the HB-IJL avoided a collision through high situational awareness and immediate braking.
- The crew of the G-GNTZ did not perceive the near-miss during their takeoff roll.
- Nighttime conditions and rain were present at the time of the occurrence.