Pilot got conflicting warnings
BERLIN, Germany -- An air traffic controller's warning to a Russian pilot to descend came one second after the jet's onboard computer told him to climb, investigators say.
An examination of the voice recorders from the two jets involved in last week's midair crash that killed 71 people revealed the contradictory instructions, German investigators said Monday.
President Vladimir Putin made an unexpected visit to the Russian town of Ufa to pay his respects to the 45 schoolchildren from the town who died in the crash. (Full story)
According to the German air accident investigation agency BFU, automatic onboard collision avoidance systems told the Russian passenger plane to climb and the DHL cargo jet to descend.
The simultaneous computer instructions came about 45 seconds before the planes collided over southern Germany.
But one second later, a Swiss air traffic controller handling the planes told the Russian pilot to descend, the voice recorders showed, according to investigators.
When the pilot did not respond, the controller repeated the instruction 14 seconds later, after which the pilot began descending, the recorders showed.
Both the Bashkirian Airlines Tu-154 and the DHL Boeing 757 were fitted with the TCAS Traffic Alert and Collision Avoidance System, the BFU said.
"About a minute before the collision both TCAS systems gave the warning 'Traffic, traffic.' About 15 seconds later the TCAS in the Boeing 757 gave the command 'descend, descend' and the TCAS in the Tu-154 the command 'climb, climb,'" the BFU said.
"About one second after this warning, the crew of the Tu-154 received an instruction from Zurich air traffic controllers to descend," BFU said in a statement.
Jean Overney, head of the Swiss Air Accident Investigation Bureau, told The Associated Press: "In the West, the pilot must follow the plane's collision avoidance system" even when it conflicts with the controller's instructions.
Overney said he didn't know if Russian pilots followed different rules.
The Swiss air traffic control body Skyguide, which was handling the planes at the time of the crash, has been facing mounting criticism for its role.
German officials on Monday confirmed published reports that German air traffic controllers tried to warn their Swiss counterparts of the impending crash but that telephone lines were busy.
Controllers in Karlsruehe, Germany, received an automatic radar warning two minutes before the crash. They tried to call Zurich tower but could not get through because of telephone problems.
Investigators have said Zurich tower's main phone system was being repaired at the time of the crash. Zurich's automatic collision warning system also was down for repairs.
The lone Zurich controller was on a back-up phone just before the crash, making repeated unsuccessful attempts to contact another German airport about another flight, investigators said.
The controller told the Russian jet to descend about 90 seconds after his last attempt to place the call, investigators said.
Prosecutors in Switzerland have begun a criminal investigation to determine if negligent homicide charges should be brought against anyone.
All of the bodies have now been recovered from the crash site, which is scattered across 30 kilometres (20 miles) of southern Germany near the Swiss border, police said Monday.
The final two bodies were removed Sunday evening. Officials have identified the remains of 43 victims.
In addition to 52 children, the Russian jet was carrying 12 crew members and five adults.
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