What happened
On March 9, 2010, at 08:42 UTC, two Alitalia Airbus aircraft, an A319 with registration I-BIMI and an A320 with registration I-BIKF, experienced a loss of separation near the VERNA waypoint.
Flight AZA1629, an A320 (I-BIKF) traveling from Milan Malpensa to Bari, requested a climb from FL350 to FL390 due to light turbulence. Shortly after, flight AZA432, an A319 (I-BIMI) traveling from Rome Fiumicino to Munich, entered the same sector at FL380.
At 08:41:24, the Short Term Conflict Alert (STCA) was triggered on the air traffic controller's radar screen. The controller immediately issued instructions for both aircraft to turn right by 20 degrees and directed AZA1629 to descend back to FL370 while instructing AZA432 to climb to FL390. During these maneuvers, the aircraft reached a minimum separation of 5.18 nautical miles laterally and 1,100 feet vertically. The A319 (I-BIMI) also experienced a TCAS Resolution Advisory (RA) during the event.
The investigation
The ANSV investigation focused on the actions of the Padova ACC (Area Control Centre) SUS sector team. The investigation examined the workload and coordination between the Executive Controller (EXE) and the Planner Controller (PLN).
Investigators found that the PLN was simultaneously acting as an On-the-Job Training Instructor (OJTI) for a trainee controller. This dual responsibility, combined with the need to manage an unscheduled traffic transfer from the Milan sector, diverted the PLN's attention. The investigation also reviewed radio communications, noting that the EXE controller was unaware of the presence of the A319 (I-BIMI) until the STCA alert activated, as the aircraft's initial contact was perceived as a new arrival rather than a conflict risk.
Findings
- The primary cause of the event was the loss of synergy between the Executive and Planner controllers due to the PLN's simultaneous instructional duties.
- The Executive Controller's limited experience contributed to the failure to recognize the potential conflict with the incoming A319 (I-BIMI).
- The PLN's attention was fragmented by the requirements of training a trainee and managing complex traffic coordination from a neighboring sector.