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Ask the Captain: What exactly is turbulence?

John Cox
Special for USA TODAY
Buckle up: It takes only a small amount of altitude loss to produce the sensation of “falling,” or negative G.

Question: What exactly is turbulence? If you could somehow be magically suspended in the air outside the plane when it hits turbulence, what would you feel?

— Submitted by reader Pat Preisinger, Bellingham, Wash.

Answer: Turbulence is a change in the movement of air. The velocity, vertical motion, or direction can cause turbulence. There can be eddies created when air changes direction quickly. In addition, a high-speed stream of air (jet streams) can create turbulence on the edges near slower-moving air.

If you were outside of the airplane (magically), the effects of the turbulence might or might not be felt. Think of being suspended in water: A boat will experience turbulence over waves as it traverses a course, while a fish in the water would not. However, some turbulence or waves are so intense that both the boat and the fish would experience it.

Q: When an airplane encounters turbulence and it feels as if the bottom has fallen out, how many feet on average has the plane dropped?       

— Mark Swiercinsky, Weidman, Mich.

A: The sensation of “falling” or negative G is uncomfortable to most people. It takes only a small amount of altitude loss to produce this sensation. I have rarely seen turbulence with more than 100 feet of altitude deviation, but the passengers felt as if it was much more.

Q: During periods of turbulence, is the pilot struggling to steer the plane, in the same way we struggle for control of a car driving over large bumps or potholes?

— William Oakland, Los Angeles

A: No, usually the autopilot is engaged. If the pilot is hand flying during turbulence, he or she will let the airplane fly through the turbulence with minimum control inputs to keep the structural loads lower.

Q: Is there ever turbulence which concerns the pilot?

— Don Zerivitz, Orlando

A: Pilots do not like turbulence, but because the designers of modern airplanes have such a safety factor built in, there is no concern about damaging the airplane. The concern pilots do have is that passengers will not have their seat belt fastened and be injured, or that a flight attendant will not be secured in the jump seat.

MORE:Read previous columns

John Cox is a retired airline captain with US Airways and runs his own aviation safety consulting company, Safety Operating Systems.

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