quinta-feira, 18 de dezembro de 2008

Turned-off warning device tied to 2006 U.S. - Brazil air disaster

Turned-off warning device tied to 2006 U.S.-Brazil air disaster


The New York Times

SÃO PAULO, Brazil — A Brazilian report issued Wednesday on the collision of an American-owned business jet and a Brazilian Boeing 737 airliner over the Amazon in September 2006 put part of the blame on the American pilots for apparently turning off cockpit equipment meant to alert other planes to the smaller jet's presence.
But a dissenting report by the U.S. National Transportation Safety Board on Wednesday put the main responsibility on the Brazilian air-traffic-control system.

The crash killed all 154 people on the airliner, operated by Gol Linhas Aereas Inteligentes. The business jet, manufactured by Embraer, a Brazilian company, was being flown home by its American buyers, a charter company in New York. It was forced to make an emergency landing. The transponder, the equipment that was switched off, was American-built.

A transponder answers calls from ground-based radar and other planes and replies with the identity of the plane and its altitude, allowing the plane's position to be determined. The transponder's signals are recorded by the ground-based air-traffic system.

The Brazilian report said the business jet's transponder was running early in the flight, then it was off and then on again. The report said the cockpit voice recorder recorded Jan Paul Paladino, the second in command, when he let out an "exclamation" on noticing it was not working after the collision.
After a silence of 10 seconds, Paladino said, "I'll do that, I got that" and the transponder was switched on, the report said.

Brig. Jorge Kersul, the head of the Brazilian safety organization, known by its acronym Cenipa, would not speak to reporters via telephone. But he told reporters in Brasília that the transponder was switched to "standby" by mistake.

"There is nothing that proves this was intentional," Kersul told the Folha de S. Paulo newspaper. "No sound, no movement," he said. "There is no reason for them to do that. The most probable hypothesis is that it was turned off inadvertently."
In Washington, the National Transportation Safety Board, which is involved in the case because of the American components, said it agreed with the Brazilians' factual findings. But it stressed that "the primary mission of air traffic control to separate aircraft within positive controlled airspace was unsuccessful."

The Brazilian controllers, it said, had failed to act promptly when the transponder stopped working and two-way radio voice communication ceased. Bad software design at the air-traffic-control center may have contributed to confusion among the controllers about the plane's altitude, the report said. The air-traffic-control system had been recently modernized.

The crew of the business jet was "not in violation of any regulations," the U.S. report said. The Americans said they agreed that "safety lessons in these areas can be determined to better prepare flight crews for international operations."
The Brazilians helped the Americans to draft a recommendation to the U.S. Federal Aviation Administration to require computerized airplanes to sound a prominent warning if the transponder is not running, the U.S. report said.

According to the U.S. report, both planes were assigned by air traffic control to operate in opposite directions on the same path and at the same altitude. "The loss of effective air traffic control was not the result of a single error, but a combination of numerous individual and institutional air-traffic-control factors, which reflected systematic shortcomings in emphasis on positive air-traffic-control concepts," the U.S. report said.

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