Drowning Claimed 18 Jet Crash Victims : Aviation: Many survived impact, but were strapped upside down in seats below water line as tide rose in Flushing Bay.

Eighteen of the 27 people who died in the crash of a USAir commuter jet Sunday night drowned after the plane veered off a runway at La Guardia Airport during a snowstorm and tumbled into Flushing Bay, the New York Medical Examiner’s office said Tuesday.

Four died from burns, four died from impact injuries and one died from a combination of all three causes, the office reported.

Rescuers said many of those aboard the Fokker 28 airliner were found strapped upside down in their seats, their heads and upper bodies trapped below a water line that rose steadily with the incoming tide.

The Medical Examiner’s office said that two of those who drowned suffered fractures “that played a contributing role in their deaths.”

That would appear to indicate that at least 16 of those aboard the jetliner died after surviving the impact of the crash and the fire that enveloped the wreckage.

The National Transportation Safety Board, which is heading the investigation of the crash of Flight 405 said Tuesday night that it had not yet received a report from the Medical Examiner’s office and could not comment on the findings.

The NTSB’s attention continued to focus on possible icing problems Tuesday as its investigators went on with their search for clues.

Although the twin-engine plane was sprayed twice with an alcohol solution to rid it of ice as it waited for a departure clearance from La Guardia, the aircraft sat in subfreezing temperatures and falling snow for half an hour more before the ill-fated attempt to take off from Runway 13.

Witnesses said the plane lifted off slightly on takeoff and then fell back to earth, tumbling into the shallow waters of the bay in a ball of flame. Of the 51 aboard the Cleveland-bound flight, all 24 who did not die were injured.

“It looks like a classic case of wing ice,” said Dick Russell, a retired United Airlines pilot who now works as an independent safety consultant and as an adviser to the Air Line Pilots Assn. Ice can distort the shape of a wing and reduce its ability to lift.

Russell said the weather conditions at the time of the accident--31-degree temperatures, falling snow and a dew point near freezing--were conducive to the buildup of ice on a sitting airliner.

“Thirty minutes is a long time to wait in that kind of weather,” Russell said. “The pilot probably thought he would be cleared for takeoff sooner.”

It is the responsibility of the pilot to make sure a plane is free of ice before takeoff.

Scrape marks and the position of the wreckage indicate the plane veered to the left as it was lifting off. Russell said that could have resulted from uneven icing.

He said the light winds noted at the time could have made the ice build up faster on one wing than the other. If the left wing had more ice, it would have stalled, or lost its lift, first, and that would account for the plane veering to the left.

Russell said that most modern jetliners, like the Boeing 737 and DC-10, are equipped with slats along the leading edges of the wings that can be extended to provide additional lift and compensate for the degradation caused by ice. But the F-28 does not have slats.

Three years ago, an Air Ontario F-28 crashed while taking off during a snowstorm in Canada, killing 23. The final determination has yet to be made on the cause of that accident, but icing is considered a strong possibility.

Five years ago, a Continental Airlines DC-9--another plane that does not have slats--crashed while taking off during a snowstorm in Denver, killing 28. The NTSB ruled that wing ice was a major factor in that crash.

Most of the wreckage from Sunday’s crash ended up in the water, but by Tuesday, all of it had been hoisted from the bay and hauled to a nearby hangar, where the NTSB experts were hard at work.

While the safety board’s findings were still limited, John Lauber, the NTSB member heading up the probe, said that several of the large worm-gear “jackscrews” that actuate the plane’s wing flaps were found to be in a partially deployed position.

Wing flaps, like slats, are used to increase a wing’s lifting capacity, and Lauber said the partial extension would be a typical setting for takeoff when there is slush on the runway, as there was Sunday.

Experts in Washington continued to review tapes from the plane’s cockpit voice recorder and flight data recorder--both of which were recovered in good shape from the wreckage--but Lauber said Monday night that preliminary readouts provided no definitive evidence as to what caused the crash.