© St. Petersburg Times, published September 15, 2001
WASHINGTON -- The FBI is analyzing three voice and data recorders recovered from airplanes involved in Tuesday's attacks.
FBI Director Robert Mueller said Friday that the agency has gotten information from the flight data recorder recovered in the crash of American Airlines Flight 77, which slammed into the Pentagon. He declined to say what information the FBI received from the recorder, which tracks an airplane's flight movements for the last 25 hours.
He said the agency had not gotten any information from the voice data recorder from Flight 77.
The voice data recorders contain radio transmissions and sounds in an airplane's cockpit for the last 30 minutes of its flight. It picks up engine noises, communications with air traffic controllers, and conversations in the cockpit.
The flight data recorder picks up altitude, heading, speed and other airplane system operations.
Also recovered was the flight data recorder from United Airlines Flight 93, which crashed near Pittsburgh. Mueller did not mention whether the FBI had gotten data from that recorder.
Still missing are the voice recorder from United Flight 93 and both recorders from the two planes that destroyed the World Trade Center.
The boxes are in the tail of the airplane. They emit beacons to help rescuers find them.
Officials at both American Airlines and United Airlines said the black boxes aboard their doomed planes were modern solid-state versions. Such devices are more resistant to damage than older magnetic tape recorders.
Experts agreed, however, that finding the recorders, while important for investigators trying to piece together the cause of an airline accident, may be less significant in this case.
"The exact air speed of the planes and the specific point of engine rotation are probably not going to be very valuable to the FBI's analysis," said James Burnett, a former chairman of the National Transportation Safety Board.
- Information from the Chicago Tribune was used in this report.