Magazine article Science News

Clearing the Air about Turbulence: A Fearful Flier's Foray

Magazine article Science News

Clearing the Air about Turbulence: A Fearful Flier's Foray

Article excerpt

It's an embarrassing confession: I'm a space science reporter, but I'm afraid to fly.

It's not the takeoffs. It's not the landings. It's that eternity in between, when the jumbo jet is cruising 30,000 feet above solid ground. Each time the seat belt sign comes on, my heart starts racing and my stomach begins doing flips.

I dread even the hint of turbulence.

Despite my fears, I have to admit I've been lucky--at least until April 16, when I boarded United Airlines Flight 925 from London to Washington, D.C. As usual, I asked to meet the pilots. While we shook hands, the captain, a man named Dan, assured me there would be only "a bit of weather" as we neared the U.S. coast--and even that promised to be minor.

The first part of the trip was indeed smooth. When the sign telling passengers to fasten their seat belts came on 6 hours into the flight, there was nary a cloud 9 in the sky and I had no more than my usual anxiety. Then the plane began shaking violently. Pilot Dan ordered the flight attendants to their seats.

Up and down, up and down. A few moments of calm and then trapped once more in a plummeting elevator. A rattled stewardess yelled a warning to watch out for objects flying through the air. I gripped my wife's fingers tightly in one hand and my sister-in-law's hand across the aisle in the other. My eyes were shut, waiting for the roller coaster ride to end. Or for the plane to crash.

Then, after a few last tremors, the turbulence was over. A food cart had tumbled on its side, and the dinner-not that anyone was hungry-was in ruins. In a shaky voice, the stewardess announced that the last few minutes had been the worst turbulence she had experienced in 20 years of flying.

Strapped tightly in my seat, I prayed we would land without another encounter.

Aviation experts define turbulence as random, unpredictable motion that occurs at the boundary between layers of air moving at different speeds. Just as the smooth flow of an ocean wave breaks up into a maelstrom of swirls and eddies when it crashes on the shore, uniformly moving layers of the atmosphere that brush against each other fragment into vortices, and other small-scale disturbances.

Turbulence is often triggered when energy released by the sun-warmed ground or by a group of forming clouds heats a parcel of air at low altitude. The heated parcel rises, distorting the windflow pattern at higher altitudes and generating chaotic motion.

Although rarely powerful enough to toss a 747 around, turbulence is essentially "a natural state of the atmosphere," says Larry Cornman of the National Center for Atmospheric Research (NCAR) in Boulder, Colo, In a thick fluid like molasses, friction between molecules smoothes out differences in motion and allows only broad, sluggish movements. In contrast, air molecules have very little friction between them. Thus, when parcels of at different speeds encounter each other, they're more likely to break up into turbulent, unpredictable patterns, he notes.

According to the Federal Aviation Administration (FAA), turbulence is the leading cause of nonfatal accidents to airline passengers and flight attendants, costing commercial airlines in the United States an estimated $100 million a year. From 1981 to 1996, the major air carriers reported 252 incidents of turbulence, resulting in 2 deaths, 63 serious injuries, and 863 minor injuries. Seat belts help avoid accidents: Both fatalities and 61 of the 63 passengers who were seriously injured were not wearing them. Last December, turbulence caused a Boeing 747 en route from Japan to Hawaii to plummet 100 feet. An unbelted passenger died after her head hit the ceiling. More than 100 others were injured.

Pilots and meteorologists don't always know when turbulence will strike, so buckling up only when the seat belt sign comes on isn't a reliable way to avoid injury Storm clouds and heavy rain are good indicators that turbulence lies ahead, but about half of all passenger aircraft encounters with choppy air occur in cloudless skies, says Cornman. …

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