sábado, 6 de dezembro de 2008

Legacy pilot turned off transponder in Gol accident

Saturday, December 6, 2008, 00:19 | Online

Legacy pilot turned off transponder in Gol accident

Air Force indicates error by air traffic controllers and communications interference by another plane

Tânia Monteiro, of O Estado de S.Paulo
BRASILIA - The Air Force concluded a report indicating what caused the second largest tragedy in the history of Brazilian civil aviation, which left 154 dead, on September 29, 1006. The analysis which will be released next week shows that the Legacy jet's transponder, a device which could have avoided the accident with the Gol Boeing, because it would have warned of the collision, was inadvertently turned off at the hand of one of the pilots - 7 minutes after the jet had passed over Brasilia. The equipment was only turned back on 3 minutes after the collision, when the Americans perceived that it had been in standby. In all, the transponder remained inoperative, without transmitting signals to Brasilia radar, for 58 minutes.

One speaks of the central points in the chain of errors by the Legacy pilots and the air traffic controllers, shown in a detailed and precise animation - more than two hours long - done by computer, based on data collected from the aircraft's black boxes. According to the Air Force, the problems began with the controllers in São Jose dos Campos, from where the airplane took off.

The operator who monitored the Legacy was not clear in giving his instruction to the pilots, saying that they should fly at 37,000 feet on the segment from São José dos Campos to Eduardo Gomes (the Manaus airport). In truth, they should have followed this altitude to Brasilia, when they should have changes altitude, changing again at they flew over Mato Grosso. Other errors by the controllers happened when the Legacy flew over Brasilia. The sergeant on duty did not see that the jet was not following its flight plan and did not change altitude. He also did not notice when the transponder was turned off.

There was a new error when, at the change of shifts, the new operator was informed, incorrectly, that the Legacy was flying at 36,000 feet, although it was at 37,000, on a collision course with the Gol. The operator also did not see or did not check with the pilots why the jet's transponder was off. The Legacy and air traffic control went almost 50 minutes without communication. And, afterwards, when the monitoring of the Legacy was handed off to Manaus, once more the incorrect altitude information was transmitted.

As to the pilots, the Air Force shows that they were not familiar with either the craft they were flying or with the rules of flight used in Brazil, which follows the standard of the International Civil Aviation Organization (ICAO, in the English abbreviation). This standard determines that the flight plan should be rigorously followed.

The American pilots followed the procedures of the Federal Aviation Administration (FAA), which are in force in the United States, which determines the maintenance of the flight plan until the tower orders otherwise. [NT: the original says "flight plan" here even though the sense would indicate "clearance"]

Third Airplane

If the serial errors by the pilots and controllers were not enough, knocking down one after another the safety barriers that might have avoided the second worst accident in the history of Brazilian civil aviation, with 154 dead, some unlikely coincidences and unexpected facts contributed to the tragedy. After desperate attempts to speak with the controllers in Brasilia, the last communication that the Legacy pilots tried to make with Cindacta-1 was not heard by ATC in the federal capital because another aircraft that was passing through the region used its call button at the same instant.

The problem is that, when two radios make this call at the same time, neither of the two speak and the receiver also hears no one. After this, the Legacy did not manage to call Brasilia because the radio frequency it was using was no longer in range of CINDACTA-1.

On the previous call, the Legacy's pilot asked Brasilia to repeat the frequencies that it should be using. The pilot only managed to hear the first three digits of the numeric sequence 123.32 Mhz, without hearing the decimal digits. When the Legacy asked for the frequency to be repeated, Brasilia no longer managed to hear it.

New directives

The FAB does not seek those to blame for the accident, but rather the factors that contributed to its occurrence. The objective is to issue recommendations to avoid other tragedies happening through commission of the same errors. Because if the collision between the Gol and the Legacy, 65 new recommendations have been sent to different bodies linked to civil aviation, in Brazil and overseas, to improve flight safety conditions. The need became clear, after the tragedy, for the pre-established rules for pilots and controllers to be followed rigorously.

One of them proposes that the transponder's functionality be improved, since it was found that it's possible to confuse data for the device with data for the plane's radio. Besides this, the equipment can go into standby if the pilot is careless. Another recommendation, valid for both CINDACTA and for airplane manufacturers, asks that the system of visual alerts be improved and even that an audio alarm be created that would be set off when the transponder stops operating.

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