WASHINGTON -- The Delta Connection flight that crashed on approach to Detroit Metro Airport on Jan. 9, killing 29 people, went through an uncontrolled roll to the left and then a jerk in that direction a few seconds before the crash, according to information released Monday night by the National Transportation Safety Board.
The partial picture given by the board indicates possible icing or a mechanical malfunction, outside experts say, and that one wing was giving more lift than the other. The problems began as the Embraer 120 slowed down, which is when icing accidents tend to occur. Investigators, however, have said they found indications of a problem with the right engine as well.
The plane was operated as part of the Delta Air Lines system by a Cincinnati-based airline, Comair.
Paul Schlamm, a spokesman for the board, citing information from the flight data and cockpit voice recorders, said the flight proceeded normally until about 38 seconds before the crash. The twin-engine turboprop was leveling off after descending to 4,000 feet and slowing to about 190 miles an hour.
Air traffic controllers had told the pilots to make a 90-degree turn to the left, which they did. The plane then started to roll to the left, with its left wing dipped at a 20-degree angle. That occurred even though the cockpit controls for the ailerons, the movable wing panels that make the plane roll to one side or the other, were positioned, apparently by the autopilot, for a right roll.
At 29 seconds before the crash, the angle to the left had increased to 30 degrees, which is the largest angle that commercial flights generally experience. At that point the rudder, which can also control roll, was deflected to the right, too, according to the board.
As is its usual practice, the safety board said it did not draw any conclusions in the early stage of the investigation.
But three experts in accident investigation who are not working on this crash said that uncommanded rolls can be caused by ice buildup.
Pub Date: 1/15/97