Aviation: AAIU releases final report on near collision above Bulgaria

Written by on January 6, 2018 in Bulgaria - Comments Off on Aviation: AAIU releases final report on near collision above Bulgaria

The Bulgarian Aircraft Accident Investigation Unit (AAIU) has concluded its investigation into a severe incident in the skies above Bulgaria, which took place on September 8, 2016. It was a near collision between two aircraft heading towards Istanbul. Had the planes collided, many lives would have been lost.

On that day, some 16 months ago, an Airbus A321 owned by the Turkish airline AtlasGlobal was en route from Zurich to Istanbul, cruising at an altitude of 35,000 feet, 140 nautical miles southeast of the Bulgarian capital Sofia, and 130nm northwest of Istanbul, when it was cleared to descend by the controllers at Sofia Center. But instead of descending, the aircraft started climbing.

At the same time, a Turkish Airlines Boeing 737 was on its way from London Gatwick to Istanbul, passing the same coordinates. This flight was cleared to descend to 33,000 feet, by the Bulgarian flight controllers.

As a result of the events in the skies above Bulgaria, both aircraft had the same altitude for a while. They were separated by only 1.2nm, when Sofia Center ordered the AtlasGlobal plane to turn left immediately, and the Turkish Airlines Boeing to turn right, in order to prevent the planes from colliding.

According to the AAIU’s final report released in Sofia, the main cause of the dangerous incident was the vertical speed selection entered into the autopilot on the Airbus A321, which resulted in the aircraft climbing, instead of descending, even though the instruction to descend was read back to the controllers correctly, the Aviation Herald reports.

The flight controllers at Sofia Center expected the A321 crew to concur, while instructing the Boeing pilots. This 2016 incident therefore happened due to a combination of events, including a mistake on the part of the Airbus pilots.

Mid-air collisions of large passenger jets are rare occurrences. In 2006, 154 passengers and crew members died in a collision of that kind above the Amazon in Brazil. In 1996, 349 people were killed in another mid-air collision in Indian airspace.


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