For too many passengers, the word "turbulence" when spoken over a public address system in flight conjures up scary images of things being tossed all over the cabin and a cockpit full of sweating pilots fighting for control.
And why wouldn't it? Between our constant warnings to keep your seat belts fastened in flight and Hollywood's obsession with the myth that airliners just stop flying and drop like a rock when they hit any bumps in the air (accompanied by hundreds of screaming extras), the word and the very concept of "turbulence" have taken on a dark and sinister nature.
But Reality No. 1 is this: Almost all the in-flight turbulence airliners fly through is absolutely not threatening or dangerous, and we pilots work very hard, and with almost perfect success, to avoid the type that is.
A boat pushing through choppy waters provides a fairly good analogy. The ride can be pretty rough, even to the point of throwing you around, but as long as the boat is sturdy and designed to be at home in such conditions, there's no danger to the boat -- only danger to people if they're knocked to the deck.
While there is absolutely no such thing as an "air pocket" (sorry, Hollywood), air does have bumps. More clearly stated, our atmosphere is seldom a still, quiet ocean of stable air molecules just sitting side by side with no vertical or horizontal currents. If it was, we wouldn't be having this discussion, because there would be no turbulence.
Instead, our atmosphere is filled with updrafts and downdrafts and jetstreams and different currents of air at different temperatures swirling and blowing and rising and falling, and sometimes coming together like the roiled waters of two streams converging. When our wings fly through those changing currents and disruptions, they act like spring-loaded, shock-absorbed wheels on a bumpy road and the smooth ride of the attached fuselage we're in becomes shaky -- sometimes so much so that it can knock us off our feet if we're trying to walk down an airborne aisle.
Reality No. 2: Airliners are designed to easily take far more turbulence than we can handle personally. In other words, it may scare us silly but it can't hurt the airplane.
Modern jetliners are very strong, well-engineered machines designed to flex and twist and absorb even the type of airborne shaking we call "severe turbulence" (which we avoid like the plague). To a jetliner, bouncing along in moderate turbulence that can scare you to death and throw things around an unsecured cabin is just another day at the office -- what it's designed to do.
Severe turbulence is something we very seldom encounter and are prohibited from flying into. This class of extreme wind currents is encountered mainly in thunderstorms and other major weather disruptions, which airline pilots are required to avoid by at least 25 miles. Since virtually every airliner has color weather radar, pilots can clearly see, day or night, the type of storms that can produce severe turbulence hundreds of miles before we get close to them.
Clear air turbulence, or "CAT," just refers to light or moderate turbulence encountered in clear air versus turbulence in clouds.
So what should you think about when we use the "T" word on the PA?