What happened
On 12 March 2011, a serious airprox incident occurred within the Geneva TMA involving two aircraft operating under different flight rules. A Dassault Falcon 2000EX, registration N994GP, was conducting a commercial IFR arrival into Chambéry airport. Simultaneously, a Cessna 210 aircraft, registration N8KR, was departing Annecy under VFR rules on a "Z" flight plan.
The two aircraft experienced a dangerous convergence near waypoint PITOM. At the closest point of approach, the aircraft were separated by only 0.3 NM horizontally and 335 ft vertically, representing an ICAO Category A high-risk collision scenario. While air traffic controllers on different frequencies provided traffic information to both crews, the aircraft were operating in a highly unstable configuration.
The investigation
The Swiss Accident Investigation Board (SAIB) examined radar recordings, flight plans, and communication logs. The investigation focused on the entry of the Cessna 210 into the controlled Class C airspace without proper authorization. Investigators also analyzed the collision avoidance system (TCAS) data from the Dassault Falcon 2000EX to determine why a resolution advisory (RA) was not issued. Technical analysis using tau diagrams confirmed that while conditions for an RA existed for approximately 15 seconds, the horizontal miss distance (HMD) filter invalidated the alert due to the specific geometry of the encounter.
Findings
- The primary cause was the unauthorized entry of a VFR aircraft into controlled Class C airspace.
- The crew of the CessNA 210 had performed incomplete flight preparations.
- There was a lack of established procedures for managing category "Z" flights departing from the Chambéry TMA.
- The convergence was characterized by a stable IFR aircraft on an arrival route and a climbing VFR aircraft.