ROSELAWN, Ind. - American Eagle Flight 4184 - its pilot fighting for control of the plane - rolled, recovered but rolled again before plunging 9,400 feet to the ground.
All 68 aboard died when the ATR-72, en route to Chicago from Indianapolis in a Halloween rainstorm, crashed upside down into a muddy field here.
The plane's "black box" shows a "rapid deflection" of the ailerons - devices on the end of the wings that control mid-air turns - after a warning alarm sounded in the cockpit, officials said Wednesday.
The ailerons' movement was "an abnormal event," says Jim Hall, chairman of the National Transportation Safety Board.
Hall says the flight data and cockpit voice recorders show:
-- Flight 4184 was holding at 10,000 feet at 175 knots (201 mph) with the wing flaps set at 15 degrees.
The plane was on auto-pilot and the wing anti-ice device was on, indicating that some icing had occurred.
-- On orders from air controllers, the plane began descending to 8,000 feet.
It picked up speed to 185 knots (214 mph), triggering an audio warning in the cockpit that the speed was too fast for a 15-degree wing flap setting.
Almost immediately, they were retracted to 10 degrees.
-- The ailerons went up and the plane made a "rapid roll to right, then recovery."
"Then the plane rolled sharply right, onto its back, and recovery was not accomplished," Hall says.
The engines were still running and the plane had 500 gallons of fuel when it crashed.
The two recorders are considered state of the art, and provide almost 10 times more flight data than those involved in the September USAir crash outside Pittsburgh.
Hall refuses to speculate on icing as a factor in the crash.
But the plane's anti-ice devices were turned on.
And the pilot of another Super ATR-72, which landed at Chicago's O'Hare international Airport 30 minutes after Flight 4184 crashed, reported an engine flameout on landing - and that an eighth of an inch of ice was on his wings.
The NTSB plans to investigate other similar ATR-72 crashes, including a 1987 crash in Italy apparently caused by icing of the wings.
