ROMULUS, MICH., NOV. 16 -- Wing flaps on a Northwest Airlines plane that crashed last summer, killing 156 persons, were in the proper takeoff position, but the jet took longer to get off the ground than expected, a witness testified today as hearings into the crash opened.

A federal investigator, however, said evidence compiled in the nation's second-deadliest air disaster indicates the flaps were not extended in preparation for takeoff.

The conflicting testimony came on the first day of National Transportation Safety Board hearings into the crash Aug. 16 of Flight 255. The only survivor was Cecelia Cichan, 4, whose parents and brother were among those killed.

Twenty-seven witnesses are scheduled to testify during the week-long hearing, but the NTSB is not expected to issue a report for months.

Douglas Allington, a first officer with Northwest now based in Memphis, testified that the flaps were in proper position. He said he thought that the plane could have become airborne if it had not clipped a light pole in a parking lot.

However, Ralph Brumby, an engineer with the airplane's maker, McDonnell Douglas Corp., said information he has reviewed pointed to the flaps being retracted. He said the flap setting Allington saw may have been an "optical illusion."

If the plane's flaps had been in the normal takeoff position, Brumby said, "it would have been about 600 feet, or two football fields, above the pole it actually struck."

Other witnesses have told investigators the plane appeared to wobble to the left and right before its wings flattened to a level position just after liftoff from Runway 3 Center at Detroit Metropolitan Airport.

The plane hit the light pole, veered to the left, hit a building and slammed upside down onto Middlebelt Road just outside the airport property.

Allington said he was in the cockpit of an airplane parked on a taxiway perpendicular to Runway 3 Center, watching Flight 255 from the time it began accelerating to the time it disappeared in flames behind the building.

"The flaps and slats were extended," Allington testified.

He said he could not estimate how far the MD80's flaps were extended but said he saw light between wings and flaps, indicating that they were extended.

Earlier today, NTSB chief investigator John Drake testified that the airplane's flight-data recorder and other evidence, including reconstruction of damaged wing-flap areas, showed that the flaps were not extended.

Drake also said a review of the cockpit voice recorder "revealed that the captain did not call for the taxi checklist before or during the taxiing of the airplane from the assigned gate to runway 3C."

Normally, flap settings are confirmed during the checklist performed as an airplane taxis to its takeoff position.

"The members of the {NTSB's} cockpit voice-recorder group did not detect any mention of the flaps or slats in the entire 32 minutes of recorded conversation," Drake said.

Flaps and slats are panels on the forward and trailing edges of an airplane's wings. When extended, they give the plane increased lift.

The setting of flaps and slats on Flight 255 has been a focus of the crash, second only in the number of fatalities in the United States to a crash May 25, 1979, of an American Airlines DC10 at Chicago's O'Hare Airport that took 275 lives.