July 4, 2002	Thursday	Rabi-us-Sani 22,1423

ZURICH, July 3: An automatic system alerting air traffic controllers that planes are on a collision course was switched off when two aircraft smashed into each other over southern Germany, Swiss aviation officials said on Wednesday.

Bashkirian Airlines, the flag carrier from Bashkortostan republic in Russia’s Urals region, whose Tupolev was travelling to Barcelona from Moscow, is to sue Swiss air traffic controllers, RIA-Novosti reported.

“The system was not working at the time,” said Roger Gaberelle, a spokesman for Skyguide, the air traffic control agency monitoring flights near the Swiss border late on Monday, when the collision occurred.

But officials denied that the two controllers on duty that night Zurich airport’s tower, which oversees traffic over the southern tip of Germany as well, acted irresponsibly.

One of the two controllers on duty was taking a break when a Russian passenger plane collided with a DHL cargo jet. All 71 people on board the two planes, including 52 Russian children, died.

While there was a general rule that both controllers have to be at their radar screens whenever the early warning system is off, this regulation did not apply when traffic is light, Skyguide officials said.

“The air traffic controllers did well when one of them took a break,” Skyguide Chief Executive Alain Rossier told Reuters. “This is completely valid (according) to our rules, especially during the night when traffic is low.”

Controllers said there were only five planes in the sector the two technicians were monitoring.

“They’re allowed to take a leak, have a smoke, a coffee, so that they can concentrate,” Gaberelle said. A “normal” workload for such a team of controllers was between 20 and 40 planes in one sector per hour, Skyguide said.

The collision warning system was shut down for routine maintenance. Normally, it beeps and flashes if two planes are on a collision path, urging the controller to take action.

Swiss controllers said the Russian airliner that collided with the cargo jet just above Lake Constance was ordered to lose altitude 50 seconds before the crash but initially ignored the orders. Both jets were diving when they crashed.

Officials said on Tuesday it was only on their third order that the Russian pilot began to lose height. But a Skyguide spokesman said on Wednesday it was no longer clear which warning prompted the pilot to react.

“We can’t say that for sure, that’s part of the investigation now,” said Christian Weiss. German investigators said the Russian pilot reacted after the second warning.

Controllers have some leeway to decide when to order jets to change altitude as long as they maintain a minimum distance between the planes — five nautical miles horizontally and 1,000 feet vertically.

“The controller reacted 50 seconds before the two flight paths crossed,” Gaberelle said. “There is a good probability the system would not have warned him before that time either.”

NOTHING RULED OUT: Officials said, however, that they could not rule out a mistake on the part of the air traffic controller on duty at the time.

“You can say he could have reacted earlier. That in itself is not a mistake,” said Weiss. “But it could be and that is part of the investigation, that this still was not according to the rules.”

Skyguide said a warning time of only 50 seconds was cutting it close, but that the time frame was well within international standards. “Fifty seconds is not ideal but not impossible,” Gaberelle said. “Technically, the timeframe is not too short.”

The air traffic controller who was on duty at the time was still receiving medical treatment. Officials said the controller was “experienced” but refused to release his age or seniority.

Skyguide said the number of planes allowed into airspace monitored by Swiss controllers had been cut by up to ten percent to reduce stress levels, but only temporarily.

Switzerland, a small country at the heart of Europe, has a higher air traffic density than most other countries in Europe. But pilots also say its traffic controllers are among the most professional in Europe.

“I have full trust in them,” said Christian Frauenfelder, an Airbus 330 pilot at Swiss. “Mistakes can happen in every complex system. But you can’t put the whole system into question because of one mistake,” he said. .

DESCENT: The black box from the Russian passenger jet has shown that Swiss air traffic controllers told it to descend only 50 seconds before the collision, and it did so within 25 seconds.

A Russian news agency, which did not specify a source, said that experts had reached this conclusion after preliminary examination of the black box.

However, it also quoted the deputy head of the Russian intergovernmental aviation committee, Rudolf Taimurazov, as saying that it would be wrong to make any final assessment about the cause of the tragedy until the inquiry was complete.—Reuters\AFP