Ask the pilot

There's no doubt that turbulence rattles the nerves of uneasy fliers, but is it dangerous?


Patrick Smith
November 3, 2006 5:30PM (UTC)

"As we cruised toward Portland, a thousand or so feet above the cottony peaks, the slamming came on with a vengeance. We requested a climb, but not soon enough. When the worst of the pummeling hit, it was like being stuck in an upside-down avalanche. Even with a shoulder harness pulled snug, I remember holding up one hand to brace myself, afraid my head might hit the ceiling."

Turbulence: spiller of coffee, jostler of luggage, filler of barf bags, rattler of nerves. But is it a crasher of planes?

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Judging by the reactions of many airline passengers, one would assume so. I'd been a commercial pilot for the better part of 10 years, a job that requires its share of impromptu coaching sessions with white-knucklers, and figured I had a pretty good grasp of the fearful flier mind-set. I didn't. 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 licensed therapist. Bunn founded 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. Everybody who steps on a plane is on some level uneasy, and there's not a more poignant reminder of flying's innate precariousness, and all its potential complications, than a good walloping at 37,000 feet. It's easy to picture the airplane as a helpless dinghy caught unawares in a stormy sea. Boats are occasionally swamped, capsized or dashed into reefs by swells, are they not? Everything about it seems dangerous.

Except that, in all but the rarest circumstances, it's not. And frankly that boat-airplane analogy isn't a very good one: Airplanes are much less susceptible to deadly upset than boats, and turbulence itself is quite different from a roiling sea. 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. Inherent in the design of airliners is a trait known to pilots as "positive stability." Should the aircraft be shoved from its position in space, its nature is to return there, on its own and with no drastic input from the crew. Conditions might be annoying and uncomfortable, but the plane is not going to crash. Turbulence is an aggravating nuisance for everybody on the plane, including the crew. But it's also, for lack of a better term, normal -- as naturally occurring as clouds, precipitation or a summer-day breeze.

When a flight changes altitude in search of smoother conditions, 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. After landing, pilots are sometimes approached by passengers who remark about the roughness of a flight. "Man, you must have had your hands full with that one!" Yet the crew will have little or no recollection of it having been bumpy at all. Not because they're jaded or cocky (much as that might also be the case), but because they understand the realities of atmospheric instability, and don't misinterpret those rocks, knocks and jigs. Fliers tend to overestimate the effects of turbulence by orders of magnitude. "We dropped like 500 feet in two seconds!" If I've heard that once, I've heard it a thousand times. In truth, a jetliner's altitude is rarely displaced by more than about 50 feet; its bank (turn) and pitch (nose up/down) will seldom change more than a few degrees.

"The motion created by turbulence is insignificant," adds Bunn. "In the cockpit we see the altimeter jiggle ever so slightly, but the anxious flier perceives a free fall. These sensations can be so intrusive that strategies to rationalize them, or escape them entirely, usually fail, even when aided by drugs and alcohol."

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During a wind-whipped approach, the frightened passenger is liable to imagine 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.

Much worse than turbulence itself could be an overzealous reaction to it -- as demonstrated with catastrophic results five years ago, after an American Airlines A300 was hit by the wake from a 747 ahead. The first officer responded with a needlessly violent deflection of the rudder, causing the plane's tail to fracture. The ensuing crash killed 265 people -- the second worst aviation disaster ever on U.S. soil.

Design flaws and a possibly preexisting stress crack may have played a role in the A300 crash, and wake turbulence, to be discussed in greater detail next week, is an altogether different phenomenon than the naturally occurring kind. It's unfair to say that turbulence, in and of itself, brought down Flight 587. Just how rare is such an occasion? 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.

Not that you'd know it listening to the media. Last summer, after a Sibir Airlines Airbus A310 overran a runway at Irkutsk, Russia, killing 124, news stories, including a widely disseminated item from the Associated Press, spoke of "turbulence" as a "potential cause." That one had me sputtering and dashing off another petulant e-mail to the AP. It's possible that blustery weather, together with crew error, led to an unstable approach and the subsequent overrun, but the implication was that rough air itself had somehow slammed the Airbus to the ground or swept it from the runway.

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So that I'm not accused of sugarcoating, I freely concede that powerful turbulence has, on numerous occasions, resulted in damage -- sometimes serious damage -- or injury. With respect to the latter, these are typically people who fell or were thrown about because they weren't belted in as requested. Incident archives speak of twisted ankles, broken bones and even a fatality or two. But airplanes are engineered to take a remarkable amount of punishment, and are required to meet stress-limit criteria for both positive and negative G-loads. You'll routinely see an airplane's wings flex during flight. This is to better absorb and dissipate any bumps. I once watched a fascinating video showing the wing of a 777 in a test chamber, intentionally bent to an almost unbelievable angle before its skeleton finally failed. The level of turbulence required to dislodge an engine or bend a spar is something even the most frequent flier won't experience in a lifetime of traveling.

Easy for me to say. Regrettably, none of this will mean very much to the hardcore aerophobe. As Tom Bunn sees it, irrational concerns about turbulence are symptomatic of a more general anxiety, a kind not easily placated by statistics and straight talk. "Statistics tell us the risk of crashing is one in several million flights," he says. "To the frightened flier, one in 10, one in a million, and one in a hundred million mean the same thing. They all include the term 'one.' How is the individual to know he or she will not be that 'one'? Awareness of safety as relative, rather than absolute, produces intolerable distress."

"When the cabin starts to bounce and sway," Bunn continues, "the flier may already understand aerodynamic theory and what keeps an airplane aloft. But theoretical understanding is abstract, left-brain logic. Meanwhile, the right brain, which uses visual-based, intuitive logic, 'sees' nothing holding the plane up. The left brain is saying, 'Hey, no problem,' but the right brain is screaming, 'Can't you see there is nothing underneath us!' Thus far, the left brain is able to keep the right brain balanced. But then it happens: turbulence. Now, there is a feeling, a tangible sensation, that tips the balance. The person pictures the plane falling, and feels it falling."

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To help alleviate such unpleasantness, pilots work to avoid unstable air when they can, taking their cues from weather patterns and reports from other aircraft. Some meteorological indicators are more reliable than others. Those burbling, cotton-ball cumulus clouds, particularly the towering variety that occur in conjunction with thunderstorms, are almost always a lumpy encounter. (Low-level stratus clouds, on the other hand, tend to provide smooth passage.) Flights over mountain ranges and through certain frontal boundaries will also get the cabin bells dinging. Boundaries along the jet stream are notoriously turbulent, as are various other climatic markers, many of them invisible to the eye (and to on-board radar), but decipherable from the weather data available to pilots and dispatchers before and during flight.

Unfortunately, predicting the exact location, strength and duration of turbulence is an imperfect science at best. Partly for this reason, I'm known to provide annoying, noncommittal answers when asked how best to avoid it. "Is it better to fly at night than during the day?" Maybe. "Should I avoid routes that traverse the Rockies or the Alps?" Hard to say. "Are small planes more susceptible than larger ones?" It depends. "They're calling for rain and gusty winds tomorrow, will it be rough?" Probably, but who knows. "Where should I sit, in the front of the plane or in the back?"

Ah, now that one is easier to handle. While it doesn't make a whole lot of difference, the smoothest place to sit is over the wings, closest to the plane's centers of lift and gravity. The roughest area is usually the far aft. Imagine a seesaw. As it teeters and totters, the part that moves the least distance is the center, at the fulcrum. An airplane is the same way, except two fulcrums are at work. A plane rotates around its lateral axis (the nose-up, nose-down motion called "pitch") through the center of lift, also called the center of pressure. It rotates around its vertical axis (the side-to-side swing called "yaw") through the center of gravity. Both centers will shift slightly as fuel is burned away, and depending on wing sweep, speed and angle of climb; however, they will always remain close to the areas where the wings and fuselage are joined. For the smoothest ride -- and the worst possible view -- this is your spot.

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If you're the sort who craves assurance, even when it's not totally reliable, you can always pay a visit to Turbulence Forecast. The site was launched in 2005 by Peter Murray, a confessed nervous passenger who hadn't been on an airplane in years. When business obligations suddenly made him a frequent flier, Murray set out to investigate which routes were most liable to have him grabbing for the armrest. (Had he asked me, I would have shrugged.) Murray learned there was no reliable online tool he could turn to, and decided to create one. According to Murray, Turbulence Forecast features the only worldwide turbulence view map, as well as self-updating graphics available for installation on personal Web sites, showing levels of expected bumpiness for selected regions. There's an online forum -- a kind of turbulence support group -- where fliers can share their experience. ("We dropped like 500 feet in two seconds!")

When pilots pass on reports to other crews, turbulence is graded on a scale from "light" to "extreme." The worst encounters entail a post-flight inspection by maintenance staff. There are definitions for each degree, but in practice the grades are awarded subjectively by the crew. I've never been through an extreme -- not unusual for most pilots -- but I've had my share of moderates and a few severes.

The most memorable of them took place in July 1992, when I was captain on a twin-engine, 15-passenger turboprop. It happened during, of all flights, a 25-minute run from Boston to Portland, Maine. It had been a hot day, and by early evening a forest of tightly packed cumulus towers stretched across eastern New England. As towering cumulus goes, the formations were short -- about 8,000 feet at the tops -- and extremely nice to look at. As the sun fell, it became one of the strangest and most picturesque skyscapes I've ever seen -- buildups in every direction forming a giant garden of pink coral columns. They were also deceptively, startlingly violent -- little volcanoes spewing out invisible updrafts.

As we cruised toward Portland, a thousand or so feet above the cottony peaks, the slamming came on with a vengeance. We requested a climb, but not soon enough. When the worst of the pummeling hit, it was like being stuck in an upside-down avalanche. Even with a shoulder harness pulled snug, I remember holding up one hand to brace myself, afraid my head might hit the ceiling.

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I asked Peter Murray if he's noticed any unusual trends in his data. Anecdotal evidence suggests that turbulence is becoming more prevalent -- possibly as a byproduct of global climate change. Pilots around the world report increased frequencies of, among other things, furious storms and alarmingly high winds. "Not really," says Murray. "Except that I never see the same thing twice." But turbulence is a symptom of the weather from which it spawns, and it stands to reason that as global warming intensifies certain patterns, encounters like that one I had over Maine will become more common.

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GO-AROUNDS

Re: Airport security

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I live in Japan now, and have just come back from Hokkaido. Security, though still a hassle, was filled with Japanese logic, speed and formality. My travel partner absentmindedly brought a half-finished bottle of tea with him. The guards asked him to remove it, carried it to a small device, and scanned it in under five seconds -- all with the usual politeness and smile that is expected here in such situations. In the United States, the amateur TSA checkers, who are usually untrained in the use of power, revert to base primal instincts and assume their superiority through physical force. The yelling, the brusqueness, and the complete absence of empathy are there to remind us that they are the top gorillas, the boys with the conch. And what's most worrying is the average passenger's acquiescence to such uncivil behavior from a branch of our civil service.

-- George Van Horn
Nagoya, Japan

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Do you have questions for Salon's aviation expert? Send them to AskThePilot and look for answers in a future column.

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Patrick Smith

Patrick Smith is an airline pilot.

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