Flight 111: Zeroing In On Black Boxes

Canadian searchers say they've detected the radio signal from one of the "black boxes" from Swissair Flight 111.

Divers went down three times Saturday off Nova Scotia to try to recover the flight recorder, but were hampered by rough waters and couldn't locate it. But a Canadian Navy spokesman says searchers have narrowed down the area, which is in 190 feet of water.

The black boxes which should tell investigators more about the pilots' decisions. The boxes could also confirm or rule out an on-board fire. The few fragments of of wreckage recovered so far show no fire damage. However, the biggest pieces of the plane remain in the ocean, and they may hold critical clues as to what caused this disaster.

Investigators are taking a hard look at the actions of the pilots in the final moments before SwissAir flight 111 plunged into the Atlantic, reports CBS News Correspondent Bob Orr.

U.S. aviation sources tell CBS News that, after reporting "smoke in the cockpit," the pilots demonstrated "no real sense of urgency" in trying to get the plane down.

At the very least, information from air traffic control tapes shows the pilots of the doomed jet did not take the most direct route to the airport.

The MD-11 aircraft was 58 miles from the Halifax airport and at 33,000 feet when pilots reported "smoke."

The pilots could have attempted a landing in minutes, but Canadian crash investigators say the crew was probably worried about landing on a short runway with a heavy load of fuel.

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"Their fuel condition was such that it would have been very risky probably for them to attempt a landing with that amount of fuel on board with that length of runway," says lead investigator Vic Gerden.

The pilots began what is called an "orbit," a series of turns away from the airport to descend, dump fuel, and line up for a landing.

CBS News Animation: Timeline of SR111

The plane continued its orbit for several minutes, when pilots suddenly declared an emergency. However, sources say, the jet still did not head directly for the airport. Instead it continued turning, then disappeared from radar and crashed.

Along baches near the crash site, pieces of the wreckage are washing ashore.

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