Swiss controllers failed to follow air safety rules

Controller was on break while collision alarm was disabled for maintenance


UBERLINGEN, Germany - Swiss air traffic officials acknowledged yesterday that a collision alarm system in their control tower was out of operation and that one of two key controllers had taken a break at the time of an in-flight collision Monday night between two jets that killed 71 people.

The disclosures increased suspicion among investigators that the cause of the crash stemmed at least in part from errors on the ground and not, as Swiss officials had been implying, primarily from errors by the pilot of the Russian passenger plane.

There were no survivors after the collision between the Russian passenger plane, which was carrying 52 children to a vacation in Spain, and a Boeing 757 cargo plane operated by DHL Worldwide, the courier service.

Both aircraft entered Swiss airspace several minutes before the crash and were flying toward each other at the same altitude.

As investigators from Russia joined their German counterparts yesterday in combing through the wreckage, air safety analysts increasingly focused on events in the control tower just before the crash.

It was not until about 50 seconds before the crash that Swiss controllers ordered the Russian plane to descend. The Russian pilot did not react at first, but then began to dive at the same moment the DHL pilot made a fatal decision to start descending as well.

Yesterday, officials at the Swiss air traffic control authority, Swiss Guide, acknowledged that one of the two controllers responsible for the planes had taken a break and was away from the radar screen in the minutes before the crash.

At the same time, the traffic control tower had temporarily disabled an alarm system in order to perform routine maintenance, authorities said.

Neither action by itself would have been controversial. But Swiss Guide's rules call for both controllers to remain on duty when the alarm system is not functioning.

Anton Maag, head of the control tower at Zurich airport, acknowledged the lapse in protocol in an interview yesterday with Swiss radio.

"We must take care to see that existing prohibitions are carried out better," Maag said on the DRS radio network.

The new disclosure is likely to intensify the conflict between Russian and Swiss aviation authorities, who have been trading accusations of blame ever since the two planes crashed in a fireball 35,000 feet above this lakeside village just north of the border with Switzerland.

Russian officials have been furious at Swiss officials who repeatedly complained that the Russian pilot was inexplicably slow in reacting to their warnings and orders to change course.

Maag has defended Swiss Guide and insisted that the agency gave the Russian pilot more than enough time to get out of the way.

Independent aviation experts said the Swiss were technically correct, but they questioned why the air traffic controllers had waited so long before issuing their warning. The Russian Tupolev TU-154, operated by Bashkirian Airlines, was "handed over" from German to Swiss controllers at 11:30 p.m. Monday, five minutes before the crash.

"These planes were known to be on crossing paths, and they were known to be flying at the same altitude," said David Learmount, operational and safety editor of Flight International, an aviation journal based in London.

Learmount said Swiss officials were correct in saying that the planes could have avoided each other with only 30 seconds of advance warning. But he said the Swiss had left little or no margin for mistakes.

"It's enough time, but not by much it isn't," he said. "It is only just enough."

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