What happened
On 27 June 2016, at approximately 15:45 UTC, an Air France Airbus A319, registered F-GRHX, was performing a visual approach to runway 31R at Marseille-Provence airport. Simultaneously, an Airbus Helicopters AS532 Cougar, registered F-ZWBS, was descending toward the aerodrome traffic circuit under VFR conditions.
The helicopter was operating with a failed transponder, meaning air traffic control could only maintain primary radar contact. During its flight, the Cougar crew initiated a hover without notifying the controller. This maneuver caused the aircraft to move into a position where radar contact was lost.
As the A319 proceeded on its approach, the flight paths of the two aircraft crossed. The crews did not realize the proximity of the other aircraft until after the crossing had occurred. The minimum separation between the two aircraft was measured at just 0.19 NM horizontally and 240 ft vertically. The crew of the A319 later noted that the helicopter had passed just below them, remarking that a TCAS resolution advisory would have been inevitable had the equipment been functional.
The investigation
The BEA investigation focused on the breakdown in separation and communication between the aircraft and the tower controller. Investigators examined the primary radar performance, the impact of the helicopter's transponder failure, and the management of parallel runway operations. The investigation also reviewed the frequency congestion on the tower radio and the accuracy of position reports provided by the helicopter crew during the incident.