domingo, 14 de dezembro de 2008

Aviationweek: Brazil Air Force, NTSB spar on Midair causes

Brazil Air Force, NTSB Spar on Midair Causes

By Jim Swickard

A draft final report by Brazilian Air Force investigators released yesterday on the Sept. 29, 2006 in-flight collision over the Amazon of an Embraer Legacy 600 owned by ExcelAire of Ronkonkoma, N.Y., and a GOL Boeing 737 placed the blame for the accident, which killed all 154 persons aboard the Boeing, on U.S. Legacy pilots Joseph Lepore and Jan Paladino and Brazilian air traffic controllers.
Notably, the U.S. National Transportation Safety Board (NTSB) strongly disagreed with the Brazilian conclusions regarding the Legacy pilots' actions as a causal factor, noting, "The crew flew the route precisely as cleared and complied with all ATC instructions," as did the GOL airlines crew.

Both the Brazilian investigators and the NTSB agreed that prior to the collision the Legacy's transponder ceased transmitting, most likely as a result of being inadvertently set to standby mode. The report said that Brazilian controllers handling the flight failed to note that its Mode C altitude information disappeared from the data block on their radar displays and was replaced by invalid data. To compound matters, it said, radio contact with the Legacy was lost and this condition went unnoticed by controllers and, initially, by the Legacy crew, who later made multiple attempts to contact ATC but without success. The crew continued at their last assigned altitude until the collision.

After the collision, the business jet, an executive version of the EMB135 regional jet on a delivery flight to New York, made an emergency landing at a remote airfield while the Boeing 737 went out of control, broke up and crashed in the Amazon rain forest, killing all 148 passengers and six crewmembers.

The Brazilian military operates that country's air traffic control system, conducted the investigation and authored the report. The NTSB participated in the investigation as the country of manufacture of the Boeing 737 and as the country of registration of the ExcelAire Legacy. The board's comments were published on the NTSB web site simultaneously with the Brazilian report.

Essentially, the Brazilian Air Force Report accuses the Legacy crew of poor airmanship, lack of proficiency in international operations and insufficient knowledge of the aircraft systems.

Meanwhile, the NTSB listed as the accident's probable cause the failure of the Brazilian ATC system to separate aircraft in positive control airspace. Specifically, it said:

*The evidence strongly supports the conclusion that this accident was caused by Legacy N600XL and GOL Flight 1907 following ATC clearances which directed them to operate in opposite directions on the same airway at the same altitude resulting in a midair collision.

*The loss of effective air traffic control was not the result of a single error, but of a combination of numerous individual and institutional ATC factors, which reflected systemic shortcomings in Brazilian air traffic control concepts.
*Contributing to this accident was the undetected loss of functionality of the airborne collision avoidance system technology as a result of inadvertent deactivation of the transponder on board N600XL and inadequate communication between ATC and the N600XL flight crew.

The NTSB said the Brazilian controllers were in full contact with the GOL crew and had ample opportunity to assign another altitude or change heading, either of which should have averted the head-on collision.

The Brazilian report noted that a parallel criminal investigation conducted by state prosecutors, "caused mistrust among the air traffic controllers who started refusing to be interviewed by the commission." Prosecutors filed criminal charges against four controllers and the U.S. pilots. Trials are pending.

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