Thin Ice Layer Could Have Impaired Takeoff by Jet, Safety Panel Is Told

DENVER — A panel investigating the crash of a jetliner here during a snowstorm was told Wednesday that ice on the wings only .03 of an inch thick--like the grit on fine sandpaper--could have seriously impaired the plane’s ability to lift off and fly.

There has been conflicting testimony at the National Transportation Safety Board hearings this week as to whether ice accumulated on the DC-9 during the long wait Nov. 15 between de-icing on the ground and the unsuccessful attempt to take off from Stapleton International Airport on a flight to Boise, Ida.

However, a 2-year-old letter from McDonnell Douglas, manufacturer of the plane, warned that “ice accumulation on the upper wing surface is very difficult to detect,” and NTSB investigators have said the same thing.

Waited 27 Minutes

In revised figures submitted Wednesday, NTSB experts said Flight 1713 waited more than 27 minutes in falling snow after de-icing before the takeoff crash that killed 28 of the 82 aboard.

Ralph E. Brumby, a McDonnell Douglas aerodynamics expert, testified Wednesday that the roughly .03 inches of water that fell as snow during the period could have created “roughness” on the wings “that could have caused the plane to stall at the speed it stalled.”

He said the individual particles of ice on the wings need have been only about twice the size of single grains of table salt to have seriously disrupted the smooth flow of air over the wings and dramatically reduce their ability to carry the big plane to safety in the critical moments after liftoff.