Crash Pilots Had to Scrap Computer’s Takeoff Data

The pilot and co-pilot of Northwest Flight 255 were forced to calculate their own wing-flap settings and other takeoff conditions after a switch in runways rendered their computer analysis useless, a newspaper reported today.

The MD-80 jetliner crashed on takeoff Aug. 16 from Detroit Metropolitan Airport in the nation’s second-worst aviation disaster, killing 156 people.

Normal procedures dictate that airline personnel give flight crews a computer printout containing suggested takeoff speed and flap settings, based on the plane’s weight, center of gravity, runway assignment and direction of takeoff.

National Transportation Safety Board investigators told the Detroit News that the calculations on Flight 255’s computer printout were based on the assumption that the pilot would take off to the southwest on a 10,500-foot runway.

But as the plane began to taxi, air traffic controllers switched the flight to an 8,500-foot runway that would head the plane to the northeast, forcing the crew to scrap the computer analysis, the newspaper said.

The task was complicated by wind direction. The flight departed with a slight tail wind, making takeoff more difficult and requiring a longer runway roll, the newspaper said.

Capt. John R. Maus and co-pilot David J. Dodds would have had to refigure flap settings and takeoff speeds using on-board charts and equipment.

NTSB spokesman Alan Pollock said today that the aircraft crew discussed the change of runway, but there was no evidence that the crew had actually refigured the flap settings.

Investigators have determined the plane’s wing flaps were set in a neutral position when they should have been extended down 11 degrees during takeoff. The neutral settings would have been used for taxiing, and only in rare circumstances for takeoff.

The flight’s cockpit voice recorder indicated the crew did not mention flap settings, as required, while reading off their preflight checklist.