What happened
On the morning of 24 July 2015, a serious air proximity incident occurred at Geneva Airport (LSGG). A private Cessna C525, registration N990FV, was taxiing from the north apron toward holding bay Z for a flight to Glasgow-Prestwick. During the taxi, the flight crew was instructed by ground control to wait for a light aircraft to pass the taxiway.
After the light aircraft passed, the ground controller provided further instructions and directed the crew to contact the tower. However, the crew of N990FV continued forward, crossing the CAT I runway holding position for concrete runway 05 without authorization. Simultaneously, an Aer Lingus Airbus A320-214, registration EI-DEF, was performing its takeoff roll on runway 05. The two aircraft entered a converging conflict, with the tip of the Airbus wing passing approximately 24 m from the nose of the Cessna. The incident was categorized as an ICAO Category A high-risk airprox.
The investigation
The Swiss Transportation Safety Investigation Board (STSB) examined the radiotelephone communications, airport layout, and air traffic control procedures. The investigation focused on why the Cessna crossed the holding position and why the conflict was not prevented by existing safety nets or controller intervention. The board also reviewed the effectiveness of the Runway Incursion Monitoring and Conflict Alert System (RIMCAS) and the presence of "hot spot" markings on aerodrome charts.
Findings
- The primary cause was the dangerous convergence between the Airbus A320-214 on its takeoff roll and the C525 which had entered the runway area without clearance.
- The flight crew of N990FV demonstrated a lack of situational awareness regarding the holding position.
- There was a lack of a stop bar at the CAT I runway holding position on taxiway Z to physically and visually demarcate the boundary.
- The ground controller lacked sufficient vigilance during the taxi sequence.
- Air traffic control procedures for aircraft taxiing from the north apron were not sufficiently adapted to the specific risks of this intersection.
- Although a "hot spot" was identified on airport charts, there was no specific warning for the danger of incursions at this specific location.
- The RIMCAS safety net failed to effectively alert the controllers, as the alarm was not perceptible during ordinary traffic conditions.
Safety action
The STSB issued several safety recommendations to the Federal Office of Civil Aviation, including:
- A demand for the installation of stop bars at all runway intersections and thresholds to act as absolute boundaries.
- Ensuring that the risk of incursions at the intersection of taxiway Z and runway 05 is clearly indicated on aerodrome charts.
- Modifying air traffic operational procedures to require controllers to explicitly instruct pilots to "hold short" when taxiing toward high-risk holding points.
- Re-parameterizing the RIMCAS safety net to ensure alarms are perceptible even in good visibility conditions.