What happened
On June 22, 2009, at approximately 15:00 UTC, two Airbus A320 aircraft, operating flights MSR704 and AZA112, experienced a loss of separation near the Saronno VOR/DME. The first aircraft, an Egyptair flight departing Malpensa for Cairo, had been cleared to climb to FL190. Shortly after, the second aircraft, an Alitalia flight departing Milan Linate for Amsterdam, was cleared to climb to FL140.
During the climb, the separation between the two aircraft fell below the required 3 nautical miles/1,000 feet minimum. The separation reached a minimum of 1.92 nautical miles and 700 feet between 14:59:46 and 15:00:04 UTC. During the encounter, the crew of AZA112 received a TCAS "Adjust V/S" resolution advisory, prompting them to reduce their rate of climb to 500 feet per minute. While the trajectories of the two aircraft did not cross, the safety margin was significantly compromised.
The investigation
The ANSV investigation focused on the actions of the Air Traffic Controllers (ATC) at the Milan ACC (Area Control Centre) ANE sector. The investigation examined the radar data, radio communications, and the transition of duties between the outgoing and incoming controllers. The investigation also reviewed the performance of the aircraft and the impact of the handover process on traffic management.
Findings
- The outgoing controller assigned a climb level to AZA112 that was not tactically sustainable given the existing traffic.
- An inadequate handover occurred between the outgoing and incoming controllers, failing to properly communicate the differing climb performance between the two aircraft.
- The incoming controller failed to recognize the developing traffic conflict in a timely manner.
- The separation between the aircraft was influenced by the fact that the incoming controller's assessment of the climb rates was delayed, leading to a late intervention to stop the climb of AZA112 at FL110 and a heading change.