Swiss ATC media conference just held
Today’s mid-air collision over Southern Germany is, according to Skyguide (the Swiss ATC), the result of simultaneously initiated descents by both the aircraft that eventually collided. In the case of the Russian Tupolev TU-154, the descent was initiated based on ATC instructions, whereas the descent of the B-757 freighter was triggered by its TCAS.
Anton Maag, Chief of Zurich-Kloten Control Tower, and Skyguide Spokesman Patrick Herr, held a press conference today, Tuesday, to review the events of the previous night.
Between 2300 and 2400, there were no unusual occurences in Swiss air control space, with only a few aircraft in the air. Swiss ATC was handed over the Russian TU-154, which was on a East-to-West routing by German ATC at around 2330, whilst the B-757 freighter, on a South-to-North routing, was handed over by Italian ATC to Swiss ATC at 2323. Both planes were at an altitude of 36000 feet (around 11500 meters).
The Swiss controller thus advised the Russian aircraft to descend to a lower flight level. According to Skyguide’s Anton Maag, it required three attempts before this advice was confirmed by the Russian crew. As a result, the Russian aircraft began its descent very late. At the same time, the crew of the B-757 freighter was advised for reasons unclear by its TCAS to descend as well. Obviously, according to Maag, this command has to be followed immediately.
The eventual collison happened at an altitude of 35000 feet between 2335 and 2336. Both aircraft remained visible for a number of sweeps on the radar screen. Maag says there were no linguistic problems between the Swiss controller and the Russian crew, whilst Herr mentioned two “sticking points” in the context of this crash. “First, why did the Russian pilot not react immediately? Second, why did the TCAS on board the B-757 advise its crew to dive?” So apart from the question as to why the TCAS on board the B-757 did not recognize the other aircraft's descent, both aircraft were tuned to the same radio frequency, so they could both simultaneously hear their respective interaction with Zurich-Kloten tower.
Above compiled based on Swiss media reports available online.
Last edited by Alpha Leader; 2nd Jul 2002 at 10:13.