Tu-154 Pilot Got Mixed Signals

APThousands of people mourning their loss at a memorial ceremony Monday in Ufa.
BERLIN -- Cockpit voice recorders show a Russian pilot received contradictory messages from Swiss air traffic control and his cockpit collision warning system seconds before he collided with a cargo jet last week, killing the 71 people aboard both planes, German investigators said Monday.

The Bashkirian Airlines Tu-154's collision avoidance system told the pilot to climb, but he appears to have followed the Zurich tower's order to descend, putting him on collision course with the DHL International Boeing 757. The planes were over southern Germany but under Swiss control when they crashed.

Swiss air traffic control said the Zurich tower would have had no way of knowing the pilot was receiving a contradictory instruction from his cockpit warning system -- Traffic Control Advisory System, or TCAS.

"He only finds out about it if the pilot tells him," spokesman Markus Luginb?hl said. "If the pilot reacts to a TCAS alarm, he is supposed to advise the controller. And the pilot assumes responsibility for the maneuver."

Russian aviation officials said the pilot's reaction in the seconds before the July 1 crash was correct, but Western aviation experts said pilots are trained to give the cockpit warning system precedence.

According to the cockpit voice recorders, the planes' warning systems gave simultaneous orders for the Tu-154 to climb and the cargo jet to dive 45 seconds before they eventually collided.

One second later, Swiss air traffic control told the Tu-154 to descend.

The Tu-154 did not immediately respond, and the Zurich tower repeated the command 14 seconds later. The planes crashed 30 seconds after that, killing all 69 people aboard the Tu-154, including 44 Bashkortostan students headed for a Spanish beach vacation, and the two DHL pilots.

German investigators did not release a transcript of the cockpit voice recorders and refused to elaborate on any of the findings.

Investigations in Germany and Switzerland have focused on the role of the control tower in the crash, and prosecutors in Zurich have launched a criminal investigation to see if charges of negligent homicide are warranted.

Russian aviation officials, Bashkirian Airlines and Domodedovo Airport said in the case of a contradiction between the onboard anti-collision system and the air traffic controller's instructions, the ground command takes priority.

"The air traffic controller gets the last word," said Sergei Rybanov of Bashkirian Airlines.

Rybanov and Yulia Mazanova, a spokeswoman from Domodedovo Airport, where the Russian flight originated, said this is an international rule.

But Herbert Schmell, spokesman for the national airline Swiss, said the cockpit warning system should have been obeyed over ground control.

"A TCAS system makes no sense if it is overruled, especially in a phase when there isn't much leeway anymore," Schmell said.

Georg Fongern, the spokesman for Germany's pilot association, agreed, adding that the planes never should have been allowed to get so close that the warning systems kicked in.

"Never in the life of an aircraft should this system be activated, and if it has been activated there have to be a lot of mistakes and deficiencies beforehand," said Fongern.

Other experts said the planes would have had enough time to avoid each other had they both followed the cockpit warnings.

In another development, German air controllers said Monday they tried to warn the Zurich tower after receiving an automatic radar warning in the control tower about two minutes before the crash that the planes were on a collision course. But when they called, the only available line was repeatedly busy.

German investigators said last week that the telephone system at the Zurich control center was being worked on at the time of the crash and that the lone controller on duty was using the reserve line to communicate with air controllers at Friedrichshafen, Germany, about a different flight. In addition, Zurich's collision-warning system was out of service of maintenance.

Most of the wreckage from the crash has been recovered and brought to the Friedrichshafen airport for investigation and a German lab in Braunschweig is examining the flight data and cockpit voice recorders of both planes.

President Vladimir Putin made an unannounced visit to the Ufa cemetery to pay his respects during a memorial for the Russian victims in Ufa.

Speaking to the widow of the Tu-154's captain, Putin said that according to his information, "the Russian pilots were not to blame for the tragedy."

"The Russian pilots were professionals of the highest class," he was quoted by Itar-Tass as saying.