Lightning and turbulence. Did one or a combination of these things cause the crash of Air France Flight 447 over the South Atlantic on Sunday evening? The evidence, scant as it is, suggests it might have.
I was asleep in my hotel room, here in the monstrous city of Sao Paulo, just south from Rio de Janeiro, when the phone rang early on Monday. It was a reporter from the Associated Press in Brussels, shooting off questions about Airbuses and electrical storms. I had no idea that anything had happened, but he quickly had my rapt attention with word of a Paris-bound A330 that had gone missing after takeoff from Rio. "They are saying it was lightning," he told me.
I flicked on the television and tried to makes sense of CNN and the BBC as they stumbled through their coverage. The jet had encountered a violent storm, they were saying, off Brazil's northeast coast as it set off across the ocean toward Europe. An automated status message, relayed to Air France's dispatch center in Paris, spoke of electrical failure and a loss of cabin pressure. There was no mayday or distress call. The plane, and everybody on it, was missing.
Neither lightning nor turbulence is normally harmful to commercial aircraft. Let's take a minute to review each ...
Spiller of coffee, jostler of luggage, filler of barf bags, rattler of nerves. But is it a crasher of planes? Judging by the reactions of many airline passengers, one would assume so. Not until I began writing for this magazine, and fielding questions from the public, did I realize how upsetting, if you'll grant the pun, turbulence is for tens of thousands of travelers. "Turbulence is the issue," says Tom Bunn, a retired captain and founder of the nation's most popular fearful flier program, SOAR. "It is far and away the No. 1 concern among my clients."
Intuitively this makes sense. There's not a more poignant reminder of flying's innate precariousness than a good walloping at 35,000 feet. It's easy to picture the airplane as a helpless dinghy caught unawares in a stormy sea. Everything about it seems dangerous. Except that, in all but the rarest circumstances, it's not. For all intents and purposes, a plane cannot be flipped upside-down, thrown into a tailspin, or otherwise flung from the sky by even the mightiest gust or air pocket. Conditions might be annoying and uncomfortable, but the plane is not going to crash. Turbulence is a nuisance for everybody on the plane, including the crew. But it's also, for lack of a better term, normal. When pilots change altitudes and routings to avoid bumps, this is by and large a comfort issue. The captain isn't worried about the wings falling off, he's trying to keep his customers as content and relaxed as possible.
The frightened passenger imagines the pilots in a sweaty lather: the captain barking orders as the ship lists from one side to another, hands tight on the wheel. Nothing could be further from the truth. The crew is not wrestling with the beast so much as merely riding things out. Most of the time, pilots will sit back and allow the plane to buck and buffet rather than attempt to recover every lost foot or degree of heading. Indeed, many autopilot systems have a special "turbulence" mode. Rather than increase the number of corrective inputs, it does the opposite, desensitizing the system.
So that I'm not accused of sugarcoating, I freely concede that powerful turbulence has, on numerous occasions, resulted in damage or injury. With respect to the latter, it is typically people who fell or were thrown about because they weren't belted in. But airplanes themselves are engineered to take a remarkable amount of punishment, including stress limit criteria for both positive and negative G-loads. The level of turbulence required to seriously damage a plane is something that even the most frequent flier will not experience in a lifetime. Around the globe each day, about 5 million people take to the air aboard 35,000 commercial departures. Yet over the past half-century, the number of airliners downed by turbulence can literally be counted on one hand, and almost always there were extenuating circumstances.
Lightning strikes are fairly common. An individual jetliner is hit about once every three years. Regional aircraft, plying lower altitudes where there's a greater propensity for strikes, are hit about once a year. Putting that another way: Approximately 26,000 commercial jetliners and turboprops are flying around the world. Assuming a given plane is struck once biennially, 35 planes are zapped every day.
Seeing how there have been only one or two lightning-caused crashes in the past 50 years or so, it's pretty obvious that airplanes are constructed with the phenomenon in mind. Aluminum is very good at helping a plane dissipate and shed lightning's energy, which can top 300,000 amps. Composite components, used with increasing frequency on newer aircraft, are not as effective, but damage tends to be limited to superficial, non-critical areas such as winglets, nose cones, etc.
But, on those rare occasions when a strike does result in something more serious, more often than not it's an electrical issue. The electrical systems of modern jetliners are highly complex and also highly critical. Taken in whole, the electrical system is arguably the most crucial system on board -- a total electrical failure, for example, is about as dire an emergency as exists. But, the typical system employs numerous backups and fail-safe redundancies, making electrical emergencies very unusual.
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So there you have it. If nothing else, I have given you a sense of why Air France Flight 447 should not have crashed.
Except that it did.
And we are forced now to acknowledge that every so often, however seldom, normally non-dangerous phenomena turn out to be dangerous -- even catastrophically so. The odds become higher when one or more of such phenomena are encountered simultaneously.
In and around thunderstorms, strong turbulence and lightning are both often present. Reportedly, Flight 447 had flown through an area of thunderstorms just prior to disappearing. The plane was passing through the notorious ITCZ -- the Intertropical Convergence Zone. Extending several degrees from either side of the equator, the ITCZ is known for unusually tall and intense storms.
Was a run-in with one of these storms the deadly culprit? Could be. It's possible to imagine any number of storm-related scenarios. For example, an unusually potent lightning strike first knocks out the plane's primary instruments, perhaps interfering with its high-tech, fly-by-wire control system. While this shouldn't be deadly in itself, now the plane is caught in the throes of intense turbulence.
According to reports, the jet had sent an automatic status message indicating electrical problems and a loss of cabin pressure. Were these issues related? Was the pressure loss caused by turbulence-induced structural failure? What about hail? Hailstones spewed from large storms can be hazardous, cracking windows and damaging engines.
We don't yet know, but believe me, no pilot relishes the thought of having to wrestle with a rapid depressurization, significant electrical problems and a high-powered thunderstorm all at the same time. Throw in control issues and any sort of structural failure, and prospects become very, very grim.
Of course, how the plane got caught up in such a storm -- if in fact it did -- is itself a mystery. Like all jetliners, the Airbus A330 has sophisticated on-board weather radar that makes it generally easy to avoid the worst weather. And storms in the ITCZ, for all their potential menace, tend to be isolated and easy to out-maneuver. This time, something was different. How so? We might never know.
One final note on the lack of survivors ...
If the airplane hit the water after partially breaking up, or when it was in any way out of control, the chances for survival would have been nil. A ditching (water landing) seems unlikely, but that too would have presented little chance for a successful outcome. The exploits of Capt. Sully, perhaps the luckiest pilot in the world, left us spoiled. This was not the calmly flowing Hudson River in daylight. It was the storm-whipped open ocean, in darkness.
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