A transcript from the conversation between the Brazilian air control tower and the American pilots who got involved in Brazil’s worst air crash ever, with 154 dead, shows that the accident might have been caused by bad or at least badly-worded instructions given the pilots by Air Traffic Control (ATC).
In the transcript of the conversation obtained by weekly news magazine Veja the Cindacta 1 control center, based in Brazilian capital Brasília asks the Legacy plane piloted by Americans Joe Lepore and Jan Paladin to change their radio frequency, and then they maintain the following dialogue:
Legacy – Brasília, N600 transferring.
Controller – N600 squawk identification, maintaining flight level 370, under radar surveillance.
Legacy – Roger.
According to the magazine’s explanation, in the first sentence, the Legacy pilot tells Brasília that he has understood the message and that he has changed his radio frequency. N600 is the small plane’s call sign.
In his response, the air controller asks the pilot to identify his airplane through the transponder – squawk in aviation lingo – and he then instructs the Legacy to maintain its altitude at 37,000 feet.
The expression "under radar surveillance" indicates that the radar would be controlling the flight. Answering "Roger" the pilot confirms that he understood the directions.
Apparently the Legacy pilot assumed that from that time on he wouldn’t need to get in touch with air control anymore and that any change would be conveyed from the control tower to the pilot. According to the air controller’s manual, a plane under radar surveillance is not required to inform its position to the ATC since the aircraft is being followed closely by the air controllers.
"The correct would have been for the controller to complement his sentence, warning that the altitude of 37.000 feet was valid just through Brasília. It seems that there was a problem of communication between the pilot and the air control," says Brazilian major-brigadeer Renato Cláudio Costa Pereira, who was the general secretary of the ICAO (International Civil Aviation Organization) from 1997 to 2003.
Brasília’s air controllers have told investigators that they tried to reach the Legacy’s pilots five times without success. While there is a possibility that the radio’s volume was too low or even that the pilots turned the equipment off, it’s common knowledge, according to Veja, that communications over the Amazon skies between Brasília and Manaus, the capital of Amazonas state, are often disrupted.
"Planes may remain up to 15 minutes without contact with the control tower. The same happens in the stretch between Manaus and Caracas," says Varig airline’s commander í‰lnio Borges, who is the director of the National Union of Aircraft Workers. The only solution in this case, he says, is to install new antennas in the area since they are too far apart.
After flying over Brasília the Legacy’s transponder stopped working. According to the magazine, the Cindacta’s computers then malfunctioned. Although they couldn’t know the altitude of the small plane the computers automatically adjusted the altitude to 36,000 feet, while in fact the Legacy was at 37,000, in the same level as the Boeing 737 flying in the opposite direction.
The air controllers trusted the new information. 40 minutes later the crash with Gol’s Flight 1907 occurred over the Amazon jungle.