What happened
On the morning of November 23, 2002, at Zurich-Kloten Airport, a high-risk runway incursion occurred involving a Swiss Air Airbus A319, registration HB-IPS, and a Tunis Air Boeing 737, registration TS-IOK.
During a period of low visibility procedures, the crew of HB-IPS requested a "swing-over" from the ILS approach for runway 14 to runway 16 to improve efficiency. The air traffic controller (ADC) approved this request, noting that an aircraft was already departing on runway 28. Approximately 17 seconds later, the Airbus A319 was cleared to land on runway 16.
Shortly thereafter, the controller cleared the Tunis Air Boeing 737 for takeoff on runway 28. As the Airbus A319 was touching down on runway 16, the crew noticed the departing Boeing 737 and initiated an immediate heavy braking maneuver. The Swiss aircraft came to a halt approximately 50 meters north of the runway 28 shoulder. The controller, realizing the conflict, ordered the Boeing 737 to abort its takeoff, but the Tunis Air crew reported that they had already reached V1 and could not safely stop.
The investigation
The investigation examined the sequence of clearances and the operational environment at the time of the incident. It was established that the controller had cleared a landing on runway 16 while simultaneously authorizing a departure on the intersecting runway 28.
Investigators found that the controller's attention had been significantly diverted by a separate traffic issue involving a Cessna 172 (HB-CFO) that had departed ten minutes earlier with a malfunctioning transponder. This required extensive coordination and communication, creating a high-workload environment. Furthermore, the controller had not utilized a manual note or digital aid to track the approved runway swing-over, leading to a loss of situational awareness regarding the intersecting traffic.
Findings
- The primary cause was the air traffic controller's erroneous issuance of a takeoff clearance for runway 28 while a landing was authorized on the crossing runway 16.
- The controller's situational awareness was compromised by heavy workload resulting from a prior transponder failure on another aircraft.
- The use of the "swing-over" procedure, while intended to increase efficiency, introduced significant safety risks in a complex traffic environment.
- The crew of the Airbus A319 successfully prevented a collision through rapid and decisive braking.
- The crew of the Boeing 737 was unable to abort the takeoff because the instruction was received after passing the critical decision speed (V1).