What happened
On 13 October 2016, two aircraft operated by ENAC were involved in a serious near-collision at Saint-Yan airport. The first aircraft, a Socata TB-20 registered F-GGNZ, was performing a local VFR training flight. The pilot had completed an initial circuit and was executing a U-shaped landing circuit for runway 3/3L. Simultaneously, a Beechcraft 58 registered F-GNSE was preparing for an IFR training flight.
The tower controller had cleared the F-GNSE for an omnidirectional departure, provided the crew maintained visual contact with a preceding aircraft. However, the pilot of the F-GNSE received no traffic information regarding the F-GGNZ. As the F-GNSE turned left into a south-westerly heading, it intersected the path of the F-GGNZ on its downwind leg. The pilot of the F-GGNZ observed the approaching F-GNSE and performed an immediate evasive maneuver, narrowly avoiding a collision as the F-GNSE passed just meters above them. The crew of the F-GNSE did not perceive the conflict and continued their flight.
The investigation
The BEA investigation focused on the air traffic controller's situational awareness and the coordination of departures. The investigation established that the tower controller was managing heavy traffic involving several student pilots. Due to reduced visibility, the controller relied heavily on a radar display that experienced significant lag, making it an unreliable tool for real-time monitoring of aircraft in turns.
Furthermore, the investigation examined the controller's mental model of the airspace. It was found that the controller had misidentified the aircraft in the circuit, specifically confusing a TB-10 with the F-GGNZ. This error led the controller to believe a potential conflict had been resolved when, in fact, a new conflict was being created between the departing F-GNSE and the arriving F-GGNZ.