Airprox between Airbus A320 and Cessna 525 near Pescara (I-BIKU)

Incident Overview On 23 October 2007 at 16:40 UTC, a serious airprox occurred between an Airbus A320-214, registration I-BIKU, operating as flight AZA 549 from Moscow to Rome Fiumicino, and a Cessna 525 CitationJet, registration HB-VOG, operating as flight EAB 7158 from Geneva to Tivat, Montenegro. The incident took place 30 nautical miles northeast of Pescara. ## Flight Details The Airbus A320-214 (I-BIKU) was flying at flight level 340 on airway UL5. The Cessna 525 (HB-VOG) was flying at flight level 370 on airway UL612. The two routes intersected at the ARPIK point. ## Sequence of Events At 16:43:08 UTC, the crew of HB-VOG reported an engine problem to Brindisi Area Control Centre and requested to descend to flight level 150. At that time, I-BIKU was at flight level 340 on a converging route from the left, at a distance of 27.74 nautical miles. Within the next 45 seconds, the HB-VOG crew requested to proceed to an airport equipped with an ILS approach and a long runway, and asked for the distance to Brindisi airport. At 16:43:53, the crew made an immediate descent request, which the air traffic controller interpreted as an emergency. The controller, aware of the potential traffic conflict, ordered I-BIKU to turn 40 degrees to the right at 16:43:59 due to the emergency. The I-BIKU captain asked if the turn was due to an aircraft 2,000 feet above, and the controller confirmed the involved aircraft was 3,000 feet above. At 16:44:23, radar recorded a horizontal distance of 13.39 nautical miles and a vertical distance of 2,700 feet between the two converging aircraft. HB-VOG had left flight level 370 about six seconds earlier and was continuing its descent at a rate of approximately 3,000 feet per minute. At 16:44:29, the aircraft were separated by 12.26 nautical miles and 2,500 feet when a Short Term Conflict Alert (STCA) activated on the controller's radar screen. At 16:45:03, the HB-VOG pilot reported making a left turn due to traffic at a lower altitude. The controller immediately instructed a right turn, which HB-VOG confirmed at 16:45:12. The separation had reduced to 3.46 nautical miles and 400 feet. At 16:45:04, the TCAS on I-BIKU issued a Resolution Advisory (R/A) to climb. The captain disconnected the autopilot and followed the TCAS instructions to climb at maximum rate. At 16:45:18, radar recorded HB-VOG, in descent, passing below the horizontal plane of I-BIKU, which was climbing in response to the TCAS R/A. The two aircraft continued to approach each other in horizontal projection to a minimum of 0.62 nautical miles before progressively separating.