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Air Turbulence: How Dangerous Is It?

By Marc Lallanilla, Assistant Editor
2/18/2014 3:05:10 PM

Like long security lines and bad coffee, air turbulence is one of the headaches travelers face when they decide to board an airplane. But there are times when turbulence can cause more than just a headache.

The 119 passengers and crew aboard United Airlines Flight 1676 experienced severe turbulence Feb. 17 as their Boeing 737 was about to land after an otherwise-calm flight from Denver to Billings, Mont.

"There was a lot of screaming, a lot of hollering," passenger Bill Dahlin told CNN affiliate KTVQ. One woman reportedly hit the plane's ceiling panel so hard it cracked, and a baby was tossed unharmed into a nearby seat. Five people were taken to local hospitals; one flight attendant remained hospitalized the following day. [The 5 Real Hazards of Air Travel]

Gravity waves may explain mysterious airplane turbulence despite clear skies. Credit: Kuster & Wildhaber Photography, via Flickr

What is turbulence?

Turbulence - called "clear-air turbulence" when it occurs in otherwise calm, blue skies - is caused when a mass of air moving at a particular speed meets another mass of air that's moving at a different speed. It's often created by jet streams, thunderstorms, weather fronts and air moving around mountains, according to the Federal Aviation Administration (FAA).

Physicists describe turbulence as "turbulent flow," or the movement of a gas or liquid in which the fluid undergoes irregular mixing, causing changes in the fluid's speed, pressure and direction. ("Laminar flow," in contrast, is a fluid movement with constant speed, direction and pressure.)

Pockets of turbulent air can be difficult for forecasters to predict, and pilots often rely on turbulence reports from other pilots who have recently flown a certain flight path. Other clues that there might be turbulence in an area include the presence of cumulonimbus clouds, mountain ranges, and cold or warm fronts.

When turbulence turns deadly

Although it may make some passengers uneasy, turbulence is usually little more than an inconvenience. "The pilots aren't worried about the wings falling off; they're trying to keep their customers relaxed and everybody's coffee where it belongs," said Patrick Smith, pilot and author of "Cockpit Confidential: Everything You Need to Know About Air Travel: Questions, Answers, and Reflections" (Sourcebooks, 2013).

The statistics on turbulence substantiate the relative safety of air travel: Between 2002 and 2011, an average of 33 people per year were injured by turbulence during U.S. flights, and most of those injuries were sustained by crew members (who are often unseated and moving about the cabin during flights), according to the FAA.

During severe turbulence, however, life-threatening injuries can occur. In 1997, United Airlines Flight 826 was leaving Narita International Airport in Japan en route to Honolulu. After encountering several waves of severe clear-air turbulence, the Boeing 747 reportedly dropped some 100 feet (30 meters), seriously injuring 18 passengers and crew.

Two doctors onboard Flight 826 were able to assist the injured people, and performed CPR on one unconscious passenger, according to the Aviation Safety Network. The pilot turned around and landed safely in Tokyo so that medical assistance could be provided to the injured, but one passenger eventually died from her injuries.

More turbulence ahead?

Some experts are concerned that turbulence might become more common due to a warming planet: A 2013 report found that turbulence strength over the North Atlantic flight corridor could increase by 10 percent to 40 percent, and turbulence frequency could jump by 40 percent to 170 percent.

"We conclude that climate change will lead to bumpier trans-Atlantic flights by the middle of this century, assuming the same flight tracks are used," the researchers wrote in the journal Nature Climate Change.

The FAA is providing enhanced training and communication to airline personnel in an effort to reduce the incidence of injuries caused by turbulence. The agency says passengers should adhere to flight-attendant advisories, wear seat belts at all times when seated and adhere to the airline's carry-on restrictions.

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