Engineer tells travelers not to worry about fuselage cracks

Cracks from metal fatigue on planes are common, and they aren't likely to bring down a plane, a former N.C. State professor says.

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RALEIGH, N.C. — A former North Carolina State University professor and expert in materials science said Monday that travelers shouldn't worry about cracks in the bodies of commercial airliners.

Charles Manning said cracks that result from metal fatigue are a part of life. For the past 30 years, he has headed Accident Reconstruction Analysis Inc., an engineering consulting firm that performs failure analysis and accident reconstruction. Before that, he was a materials science professor at N.C. State, and he also headed NASA's Langley Advanced Materials Research Program.

"It can happen with everyday things. Take a paper clip and bend it back and forth. It's going to break," Manning said.

A 5-foot-long hole tore open Friday in the passenger cabin roof of a Southwest Airlines plane shortly after it took off from Phoenix on its way to Sacramento, Calif. The plane made an emergency landing at a military base in Yuma, Ariz., but no one was hurt.

Southwest then grounded 79 other Boeing 737-300 planes to inspect them. Small cracks were found in the fuselages of three other planes, while 19 inspected aircraft showed no problems and were returned to service. The rest of the inspections are expected to be finished by Tuesday.

Manning said that pressurizing cabins during flights so that passengers and crew can breathe comfortably stretches the metal skin of an aircraft in and out. Over time, he said, the metal wears down and cracks.

Airlines try to find cracks during routine maintenance inspections, but they usually aren't found until they are more severe, he said.

"A fatigue crack, you can't see the darn thing. They're so small, I mean, I have to look at it with my microscope," he said.

Still, Manning said, when a crack in the fuselage becomes a tear, it isn't likely to bring down a plane.

"The plane won't come apart," he said. "What will happen is that you'll lose pressurization."

The Federal Aviation Administration puts airliners on a very tight maintenance schedule, he said, and manufacturers constantly test aircraft to help determine when and where parts are likely to experience fatigue.

"I think planes are maintained as well as you can, and if the FAA sees that people are not doing it, they get after them," Manning said.



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