What happened
On April 13, 2002, at approximately 16:40 UTC, a near-collision occurred in the Geneva-controlled airspace south of the IRMAR waypoint. The incident involved an EasyJet Boeing 737-33V, operating flight EZY872 from Nice to Amsterdam, and a Nouvelair MD-83, operating flight LBT534 from Monastir to Brussels.
While EZY872 was climbing through flight level 320, it intersected the path of LBT534, which was cruising at the same altitude. Radar tracking confirmed that the two aircraft reached a minimum vertical separation of only 200 FT and a lateral distance of 1.5 NM. The pilot of EZY872 reported seeing the other aircraft on the TCAS (Traffic Collision Avoidance System) display, though no Resolution Advisory (RA) was issued.
The investigation
The investigation focused on the coordination between different air traffic control sectors. It was established that while the aircraft were in visual meteorological conditions, the controllers failed to maintain adequate separation.
Investigators found that a controller in the Aix sector had alerted a coordinator in the INS sector that EZY87 and LBT534 were in close proximity. However, during the process of authorizing EZY872 to climb to flight level 360, the controller in the MOLUS3 sector assigned a new altitude without accounting for the position of LBT534. Furthermore, the investigation revealed that the controller in the MOLUS4 sector had difficulty identifying EZY872 on the primary radar screen, necessitating the use of an auxiliary screen to locate the aircraft.
Findings
- The primary cause was a coordination error regarding the assignment of flight levels, driven by a lack of attention from the controller coordinator.
- The aircraft EZY872 was kept on the frequency of one sector even though it was transitioning through an altitude controlled by another sector.
- The transfer of the aircraft between sectors was performed prematurely while a conflict was developing.
- The air traffic controller's instruction to avoid the traffic was not sufficiently imperative given the emergency nature of the situation.
- There were discrepancies in pilot reports regarding whether traffic information was received, likely due to the time elapsed before the reports were filed.