The grounding of a Southwest Airlines 737 earlier this month due to a five-foot tear in the upper fuselage while the plane was in the air reminded me of a favorite old movie starring James Stewart.
‘No Highway in the Sky,’ a British disaster film made in 1951, follows the heroics and eccentricities of a professor and an expert in aviation who is commissioned to investigate the crash of a commercial airliner. Factoring in the age of the plane and the number of hours flown—not to mention the natural propensity of metal to weaken when under constant stress and subject to vibration—Stewart’s character theorizes that the plane crashed because the tail fell off due to metal fatigue.
He proceeds to rig a life-sized experiment in his lab, subjecting the tail section of an actual aircraft to vibrations and various in-flight sources of stress in an effort to replicate the actual crash, and to test his theory.
His colleagues think he is daft. But the movie—based on a novel—did contain some elements of truth.
That was borne out in the comments of a former North Carolina State University prof and expert in materials science, who says cracks in the bodies of commercial airliners are normal, and can be expected.
“It can happen with everyday things,” Charles Manning said in comments published April 4th on WRAL.com. “Take a paper clip and bend it back and forth. It’s going to break,” Manning said.
Of course, there are the engine vibrations—harkening back to that old Jimmy Stewart movie. But more precisely, Manning told WRAL that the act of pressurizing the cabin, allowing passengers and crew to breathe, stretches the metal skin in, and out with each pressurization. Over time, the metal wears down and cracks.
Fatigue cracks are small, he said—barely perceptible with a microscope when they first occur. It’s when they become more severe and can be seen by the naked eye, that they can potentially become a problem and are then subject to regular inspections.
Manning knows his stuff. 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 North Carolina State, and he also headed NASA’s Langley Advanced Materials Research Program. He reminds travelers that planes are inspected regularly, and not to worry…
Not to worry?
Tell that to the frightened passengers on board the Southwest airliner when the five-foot gash blew open, suddenly de-pressurizing the plane. Yes, the aircraft landed safely and there was no loss of life or injury beyond sheer terror. However, the sudden de-pressurization of a cabin can serve as a vacuum, sucking anything out with the rapidly escaping air pressure—like papers, handbags…and if the breach happens to occur adjacent to a child who isn’t strapped in…
Well, you know the rest.
In the movie, Jimmy Stewart’s character forgot to provide for temperature in his calculations. The tail DID fall off in his lab, but a bit beyond when he said it would. Sadly, during the interim, he had caused damage to a similar plane on an attempt to prevent it from taking off (he was worried about the tail), and the daft professor was banished and dismissed as a crackpot.
Until, that is, the tail in his lab experienced fatal metal fatigue, cracked, separated and crashed to the floor.
Until, that is, the actual plane he tried to keep on the ground was repaired and sent up for a test flight without passengers. When it landed, the tail fell off…
It was just a movie, right?
Fact: Three years after the film’s release, there were two fatal crashes involving the world’s first passenger jet, the de Havilland Comet. Investigators determined that metal fatigue was the most likely cause of both accidents, although other sources point to a design flaw. No the tails didn’t fall off, but the fuselage gave way.
That was in 1954.
Then there was the infamous 1988 incident where cracks led to a massive breach in the roof and fuselage of an Aloha Airlines flight. Flight attendant C.B. Lansing was sucked out due to the rapid depressurization, and she fell to her death.
Manning assures that the Federal Aviation Administration (FAA) keeps the airlines on a tight maintenance schedule, including the testing by manufacturers of aircraft in an effort to gauge when, and where metal is likely to experience fatigue.
Did they miss something with the Southwest flight?
“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.
Hey, how about this idea. Figure out the point when metal starts to experience fatigue—and replace the bloody plane.
Oh, but that would be just too expensive, wouldn’t it? Planes cost millions of dollars. Fleets cost billions. We wouldn’t have an airline industry—it would not be economically viable.
Thus to have an airline industry, it appears that planes are required to stay in service as long as they are well maintained.
Complete with cracks.
Yes, I acknowledge those who maintain flying is still safer than driving—especially with so many people abusing their smart phones and GPS devices—or looking at their computerized dashboards–while driving.
That’s why I’m taking the train…