What happened
On June 22, 2003, at 18:45 UTC, a near-collision occurred at Geneva Airport involving a SWISS flight, SWR904．, an Avro RJ1H (registration HB-IXP), and a private Pa18 (registration HB-PIC). The private aircraft was conducting a VFR circuit around Lake Geneva. After completing a 360-degree maneuver, the pilot of HB-PIC was instructed by the tower controller to overfly the threshold of runway 05 concrete to join the left-hand downwind for the grass runway 05.
Instead of following the instruction, the pilot of HB-PIC maintained a course that brought the aircraft toward the threshold of runway 23. Simultaneously, the controller cleared the Avro RJ1H for takeoff from runway 05. The two aircraft crossed paths at a horizontal distance of only 0.1 NM, with a vertical separation estimated by the pilot of the Avro RJ1H to be as low as 200ft.
The investigation
The investigation established that the air traffic controller was managing a high volume of traffic, with 17 aircraft handled on the frequency within an 18-minute window. The controller's radar screen only showed the Pa18 as a primary radar target without altitude information, as the aircraft was not equipped with a transponder. Consequently, neither the Short Term Conflict Alert (STCA) nor the Traffic Collision Avoidance System (TCAS) provided any warning to the crews.
Findings
- The primary cause was the failure of the VFR pilot to follow the ATC instruction to overfly the runway 05 threshold.
- The controller placed excessive trust in the pilot's compliance with the specific instruction and failed to verify the aircraft's actual path.
- High traffic density contributed to a lack of visual vigilance, preventing the controller from noticing the deviation in a timely manner.
- The controller assigned a non-published route to the VFR aircraft during the maneuver.
- The lack of a transponder on HB-PIC meant the aircraft appeared only as a basic primary radar target without altitude data.