Not only to fly, but to bring the world's eyes...skyward.

Monday, April 4, 2011

Structure - - FAIL. System - - SUCCESS.

got toupee?
The news media have been getting a lot of mileage out of the depressurization of a Southwest Airlines 737-300 over the weekend, replete with the sadly typical barrage of incredulity and extreme visualizations from the talking heads after playing a few sound bites from passengers high on adrenalin and low on facts.

Regardless of how many of these cats' nine lives were needlessly spent in this "accident" (the NTSB's label for any occurrence of "substantial" damage to an airplane), it was not, I say again, was NOT a failure. It was a contingency for which decades-old systems design and procedures training provided ample response, as shown by the death toll/injury count: one (1) bump on one (1) flight attendant's head.

Just like your family car, airplanes lead a life of constant trial. Every bump of turbulence, every imperfect landing, even the simple fact that an airliner spends 99% of its life fully exposed to the elements, causes wear and stress on strong, but ultimately destructible, materials. Check out this video of a 777 wing being purposely stressed far beyond any certification standards, which themselves far exceed any conditions the aircraft is expected to ever encounter in the course of its service. Note how far the wing flexes before it breaks. That's not balsa wood or plastic, kids. That's several tons of the highest-grade aluminum alloy available on Earth.
Thanks to uncompromising, costly certification and maintenance programs (among those from which the government did NOT release the airlines when it "deregulated" the industry's revenue stream in 1978), our airliners almost always endure these observable insults without incident for tens or sometimes hundreds of thousands of hours. But, in addition to the bump and grind of flying five hundred miles per hour, twelve hours a day, seven days a week for weeks on end between scheduled off-line maintenance events, airplanes bear a stealthy stress that only one other type of vehicle, submarines, ever encounter: pressurizations.

Even SCUBA tanks are taken out of service after being pressurized and depressurized a certain number of times. They're steel (I think) and they bear no structural burden whatsoever. To make the air inside the fuselage thick enough to sustain human life at 35,000 feet, an airliner's fuselage has to be pressurized (using air tapped from its engines' compressor stages) to around eight PSI.

Here's an analogy: first, just try to make a submarine using only the lightest possible materials (to make it fuel efficient and thus cheaper to operate) to give roughly thirty years' service. Then, take it down to about 20 feet (1.5 atmospheres of pressure there, analogous to the .5 atmosphere at 35,000 feet), then surface it. Repeat this tens of thousands of times, always while moving at twenty knots or so through anything from calm to heavy seas. Would you expect weaknesses to develop at some point? Would you expect some to develop that you might not be able to economically detect before it developed a manageable leak and the sub had to surface unexpectedly for repairs? Would you expect it to be international, front page news when it did? Am I making this situation seem adequately ridiculous?

To make it even more so, I'd like to point out that, unlike the sub, the physical manifestation of an airplane is really just the wing. The fuselage is just something we humans use to make the wing carry a payload for us, like a horse can carry a saddle or saddlebags. Would Jesse James have been able to carry out a train robbery already in progress if someone shot a hole in his saddlestrap? Sure. Would he set out to rob one, knowing of the weakness beforehand? Not likely.

Since the dawn of high-altitude, pressurized flight, equipment and procedures have been developed, employed, and continuously improved to allow fragile humans inside a pressurized fuselage to survive a sudden depressurization with little more than an earache to show for it. The procedure is to use a provisioned supplemental oxygen system for the few minutes it takes to get that otherwise indifferent wing to "plummet" (puh-lease) as quickly as possible from an inhospitable altitude to a livable one. We then continue to "plummet" into the nearest suitable airport, tell Geraldo about our harrowing experience, and let the bidding wars for a book deal begin. Ok, ok, you're right. Geraldo was on his field trip to Libya that day.

What occurred on that Southwest Airlines flight was this: The System Worked. It's built like a brick outhouse for a reason - so we don't have to be. Kudos to Boeing for making an airplane that survived decades of Life's abuse and still delivered its precious cargo safely back to Earth after an easily reasonable failure. Kudos to Southwest for hiring and retaining employees capable of effectively managing those failures when they happen. And kudos to the passengers for listening to them and letting them do their jobs without being second-guessed.

And shame on the media, for perpetuating the fearful flyers' illusion that the proper function of an obsessively redundant aviation safety system designed to preserve life in a hostile world, utterly without respect for cost, is actually anything newsworthy. If only it were so safe to drive to the airport.

An aviation love story...

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