What happened
On October 23, 2007, at 16:40 UTC, a serious airprox event occurred approximately 30 nautical miles northeast of Pescara involving an Airbus A320-214, registration I-BIKU, and a Cessna 525 CitationJet, registration HB-VOG.
The Cessna 525, operating flight EAB 7158 from Geneva to Tivat, experienced an engine failure on its right engine. To manage the emergency, the crew requested an immediate descent from FL 370. Simultaneously, the Airbus A320, operating flight AZA 549 from Moscow to Rome, was cruising at FL 340.
As the Cessna descended through the Airbus's flight level, the separation between the two aircraft rapidly decreased. The air traffic controller (ATC) at Brindisi ACC, recognizing the potential conflict, instructed the Airbus to turn north. However, the vertical separation dropped to just 400 feet as the aircraft trajectories converged. At 16:45:04, the TCAS on the I-BIKU issued a "Climb" Resolution Advisory (R/A). The pilot of the Airbus disconnected the autopilot and executed a maximum rate climb to avoid the descending aircraft. The two aircraft eventually crossed paths with a vertical separation of approximately 300 feet before the risk subsided.
The investigation
The ANSV investigation examined radar data, flight recorder information, and communications between the crews and Brindisi ACC. The investigation noted that at the time of the event, the minimum required radar separation in the area had been increased from 5 NM to 15 NM due to maintenance work on the Ravenna radar system. This increased separation limit meant the aircraft were already in a state of non-compliance with standard separation before the conflict became critical.
Investigators also reviewed the ATC's performance, noting that while the controller attempted to resolve the conflict, essential traffic information regarding the presence of the other aircraft was not provided to both crews. Furthermore, the investigation found that the crew of the HB-VOG was heavily focused on managing the engine failure and was unaware of the proximity to the Airbus or any TCAS alerts.