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Will black box reveal Flight 93's last moments?

Friday, September 14, 2001

By Jonathan D. Silver, Post-Gazette Staff Writer

Whatever words passed between pilots, passengers and hijackers during the final voyage of United Airlines Flight 93 may be stored in a rectangular, 16-pound orange container the size of a shoebox.

There's no guarantee, though, that the plane's cockpit voice recorder, one of two so-called "black boxes" carried by every commercial jetliner, will be brimming with data or even found intact.

While built to withstand tremendous crash forces and intense heat, neither the cockpit voice recorder nor its twin, the flight data recorder, is indestructible.

Search crews yesterday found the flight data recorder about 4:45 p.m. at the hilltop crash site outside Shanksville, Somerset County. It was in a crater gouged by the plane when it crashed Tuesday morning. The box was turned over to the National Transportation Safety Board. Officials on the scene would not say whether the box was intact.

Following a tour of the crash site Wednesday, investigators and U.S. Rep. John Murtha, D-Johnstown, noted that one or both of the boxes might have been crushed by the impact of the crash or incinerated by the jet fuel-fed inferno it ignited.

Even if the crash was not enough to destroy the voice recorder, there is another concern.

The device can be shut off by flipping a labeled circuit breaker in the cockpit or cutting electricity to the plane. There is no battery-powered back-up system.

Theoretically, then, terrorists could have prevented the recording of any shouts, screams, commands or engine noises, masking with silence the final sounds of all 45 people aboard.

If any passengers launched into desperate, last-minute heroics, as is suspected, the sounds of their struggle to overpower the hijackers and divert the plane from a populated area could be forever lost.

The cockpit voice recorder picks up conversation in the plane's cockpit through a microphone located on the overhead instrument panel and boom mikes worn on pilots' headsets. It is possible that loud sounds in the passenger cabin could also be detected if the cockpit doors were open.

That information is stored on either magnetic tape or memory chips in the recorder, which is located in the plane's tail section. Older models record the data on a continuous loop of magnetic tape that starts anew every 30 minutes; newer models hold two hours worth of data.

Ron Crotty, a spokesman for the avionics division of Honeywell, one of the largest manufacturers of cockpit voice records, said yesterday it was "pretty likely" that Flight 93 had a model that stored 120 minutes of information.

Also in the tail section is the flight data recorder, which monitors airplane functions such as speed, heading, altitude and the position of directional surfaces such as the rudder, elevators and flaps.

CNN reported yesterday that air traffic controllers listening to cockpit chatter through an open microphone on Flight 93 heard someone aboard the Boeing 757-200 say, "Get out of here."

The microphone went off and then came back on. Sounds of scuffling were heard. There was another yell of "Get out of here."

Then, CNN reported, a voice was heard in broken English with an Arabic accent saying: "There is a bomb on board. This is the captain speaking. Remain in your seat. There is a bomb on board. Stay quiet. We are meeting with their demands. We are returning to the airport."

Honeywell puts its black boxes through rigorous testing to ensure they can withstand tremendous impacts and furious fires. The housing is made from hardened stainless steel, slightly less than a quarter-inch thick.

The voice recorders are designed to resist flames that burn as hot as 1,100 degrees Celsius for 30 minutes.

Staff Writer Cindi Lash contributed to this report.



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