America Strikes Back

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Wednesday, September 12, 2001 - 04:52 p.m. Pacific

Crashes will test airliners' black boxes

By John Dowling
The Associated Press

The devastating crashes of two airliners into the World Trade Center were an extraordinary test of the "black boxes" that may hold clues to the doomed jets_ final minutes.
The crashes of the two Boeing 767s combined a high-speed impact into a steel-and-concrete grid, a long, intense fire and hundreds of tons of crushing weight, circumstances never anticipated in testing, experts say.

"There_s really no way to tell what to expect in this," said Ted Lopatkiewicz, a spokesman for the National Transportation Safety Board.

Even if the two recorders carried by each plane are intact, investigators still must find the objects — not much larger than shoeboxes — in mountains of debris.

None of the recorders from Tuesday_s four jetliner crashes in New York, Washington and Pennsylvania had been recovered as of early Wednesday evening. At a news conference, New York Mayor Rudolph Giuliani held up color photos of the recorders to show what workers were looking for, and to inform the public in case someone came across them.

Experts said black boxes are designed to withstand crashes of the sort that occurred in Pennsylvania and at the Pentagon, and the prospects of finding those recorders intact are considered greater.

Airliners carry two recorders to provide clues in case of a crash. The voice recorder is designed to capture at least the last 30 minutes of cockpit conversation. The flight data recorder notes speed, altitude, engine activity and how other aircraft systems are operating.

The bright orange recorders weigh between 15 and 30 pounds. The newest models record sound and data on the equivalent of a computer hard drive. Older recorders use magnetic tape.

The recorders are in the tail of the aircraft to cushion them from a nose-first crash. Because they are relatively small and dense, they are often flung to the edge of the field of debris from a crash.

Current federal rules require that the devices withstand being engulfed for 30 minutes in a 2,000-degree fire, equivalent to the temperature of burning aviation fuel, and withstand a weight of 5,000 pounds for five minutes. Older recorders were held to a less-stringent heat standard.

Also, the recorders must be able to withstand stopping within 18 inches from a speed of 400 mph, a quality that is tested by firing the devices from an air cannon.

"This equipment is tested for very extreme conditions, and one would hope there is a chance they would survive" the Trade Center crashes, said Tom Crain, a spokesman for Honeywell Aerospace, a leading manufacturer of the devices.

Airlines sometimes replace the recorders during maintenance, so an older jet could have a state-of-the-art recorder, said Boeing spokeswoman Liz Verdier. The two jets that hit the Trade Center were built in the mid-1980s.

United Airlines, which operated one of the jets, declined Wednesday to give any information about the recorders in the airliners. American Airlines did not return a call seeking comment.

Lopatkiewicz said there have been cases where recorders were rendered useless by fire after a crash, but he knew of no case where a recorder was destroyed by impact.

NTSB officials said they could not recall a crash on land in the United States where the recorders were not recovered. However, in a 1992 crash in the Netherlands, where an El Al 747 cargo plane hit an apartment building, the cockpit voice recorder was never recovered. Dutch officials speculated that a souvenir hunter walked off with the device.


Copyright © 2001 The Seattle Times Company


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