quote:Originally posted by A345
There have been many accidents in the past, i believe there was a Delta aircraft quite a few years back hit CAT as it was on approach and literally made the aircraft just fall out of the sky and hit the ground becasue it was so low.
The Delta incident wasn't CAT, it was due to a "micro-burst", a very sudden and violent pressure change (from low to high pressure), caused by a rapidly falling mass of cold air, caused by a storm cell in the vicinity.
http://www.math.unl.edu/~jfisher/NSF_96/windshear.htmlhttp://www.usatoday.com/weather/tg/wmcrbrst/wmcrbrst.htmThis is why many civilian airliners now have microburst detection technology built into their weather radars.
CAT is, as you suggest, pockets of "nothing" - well not quite "nothing", but lower pressure air - usually encountered at high altitudes, above most usual weather systems.
As it's name implies, CAT (Clear Air Turbulence) occurs during conditions of no other significant weather, and is therefore difficult to detect on the weather radar (i.e. turbulence is usually inside, or very close to clouds, especially around storm cells).
The sudden lower air pressure causes the airflow to detach from the wings, and the aircraft to bounce around.
Most turbulence encounters usually cause vertical movement in tens to hundreds of feet, though if you can't see an altimeter in front of you, it can feel like more. (Put the skymap on next time you are in turbulence, to see an altimeter.)
Severe turbulence can make a plane fall thousands of feet, but if that happens you will definitely know about it. Anything which is not firmly tied down will fly around the cabin. Books, glasses, cups, people, etc. It's not unknown for overhead bins to come open in these situations and their contents to fall out.
If the cabin crew are still up and around in the aisles, then it's not heavy turbulence, it's only moderate at worse.
In many cases, the flight crew will know where forecast areas of turbulence will be, through their pre-flight weather briefings. Weather Centres produce many weather charts and briefings to help pilots. Routes will be planned to avoid the worst of the turbulence.
Even then, I'm sympathetic to your situation, as a member of my family is a very nervous flyer, and would be upset by extended periods of turbulence.
Regards,
Mike