What happened
On March 31, 2014, a serious airprox incident occurred at Geneva Airport (LSGG) involving a Boeing 737-800, registration TC-JGV, operated by Turkish Airlines, and a Fokker 100, registration OE-LVL, operated by Tyrolean Airways.
During a period of clear weather, the Turkish Airlines flight was on visual approach to runway 05. To maintain traffic flow, the aerodrome controller aligned the Fokker 100 on the runway and, in an attempt to expedite operations, authorized the departure of a Pilatus PC-12 from taxiway Z before clearing the Fokker 100 for takeoff. This sequence resulted in a dangerous proximity between the arriving and departing aircraft. As the Boeing 737-800 crossed the runway threshold, it was only 1206 meters from the departing Fokker 100, significantly below the prescribed minimum separation of 2400 meters.
The investigation
The Swiss Transportation Safety Investigation Board (SUST) reconstructed the event using radio communications, radar data, and surveillance system logs. The investigation focused on the controller's decision-making and the performance of the Runway Incursion Monitoring and Conflict Alert Sub-system (RIMCAS).
Investigators found that the controller, while managing traffic, did not notice the initial visual-only alert from the RIMCAS system. When the system later issued an audible critical alert, the controller determined that instructing the arriving aircraft to go around would be more risky than allowing the landing to proceed, leading to the decision to permit the landing despite the ongoing conflict.
Findings
- The primary cause was the inappropriate integration of a departure from taxiway Z into the runway sequence.
- The controller's workload was assessed as medium, but the decision to prioritize landing over a go-around contributed to the loss of separation.
- A systemic issue was identified regarding the RIMCAS system settings, specifically that the initial phase of the alert was only visual, which went unnoticed by the controller while they were monitoring external traffic.
Safety action
Following the investigation, a safety recommendation (No. 508) was issued to the Federal Office of Civil Aviation (FOCA). The recommendation suggests that the configuration of the RIMCAS system should be reconsidered to ensure the safety net remains effective during weather conditions other than low visibility.