Metal Fatigue Dislodged Plane's Wing Panel
Wednesday, April 23, 2008
The 20-square-foot wing panel that tore off an airliner over Maryland last month has not been found, but officials have learned why it broke away, the National Transportation Safety Board said last night.
Two of the three clips that held the front edge of the panel to the wing had failed before the flight because of metal fatigue, an NTSB report said. The third clip failed during the flight of the US Airways Boeing 757, which was headed from Orlando to Philadelphia, the board said.
After the March 22 incident, the airline told the safety board that it had inspected the wing panels on all its 757s and found problems with fasteners on several, according to the board. The airline said it made repairs and returned the planes to service, the NTSB reported.
The safety board said it is still investigating the causes of clip failures and their possible effects.
In an earlier report, the NTSB said the composite panel from the left wing broke loose about 9:30 a.m. and struck several windows toward the rear of the airplane. One window was cracked.
However, the NTSB said the window's inner panel was not damaged, and the plane, which carried 174 passengers and six crew members, did not lose pressure.
In yesterday's update on its investigation, the NTSB said the loss of the panel did not substantially affect the plane's handling characteristics. The plane landed in Philadelphia without incident about 30 minutes after the panel broke loose.
An NTSB spokesman said last night that authorities think that the panel separated over Southern Maryland.