turbulence

[sammym]

I am not a pilot and I always wondered when flying what was going on in the cockpit during air turbulece. What special procedures does the pilot follow and has an aircraft ever been downed by turbulence at cruising altitude ? I know many close calls have happened { especially recently } but I can't recall crashes having occured.

[fly4fud]

The good thing about turbulences, at least for us in the pointed end, is that we don't need to stir the coffee :)

No, seriously now. We use 3 categories of turbulence, light/moderate/severe.
When the shaking becomes moderate to severe, which is already very uncomfortable to most passengers, we reduce speed. Most airplanes (at least airliners) have a rough air penetration speed called Vra or Vb. This speed will permit the structure to withstand the stresses without damage :)
Then, if the bumpy act continues, we try to leave the turbulent air zone. Descending/climbing to another level is, most of the times, helpful. An other routing might also be considered.
Of course, the aircraft could be in danger of loosing bits and pieces and even eventually crash if one would penetrate zones with severe turbulence such as thunderstorms http://www.pprune.org/ubb/NonCGI/eek.gif
As far as aircraft having been downed by turbulence, this has not happened very often (apart from windshear and such during final approach), but I do remember some accident a few years ago close to the Fuji-yama, when some turboprop aircraft lost some important parts and crashed http://www.pprune.org/ubb/NonCGI/frown.gif

Aircraft are designed from the onset to withstand severe turbulence without problem. As to the cases you might be referring to, most people were injured for not being fasten when unexpected turbulence hit the craft they were in.

Thrust me, whenever seated, make sure your seat belt is fasten!

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... cut my wings and I'll die ...

[Descend to What Height?!?]

Sammym
over the years we have on occasions gone out looking for turbulence, to try and measure it and hence get a better understanding.
It gets exciting when it's not expected, but as fly4fud says, aircraft are stressed for it, so it's no huge problem. If it ever got too exciting, the captain always had the option of scrubbing that leg of the sortie.

Flying in or next to Cu nims on the other hand can concentrate the mind wonderfuly! As here you can also get problems with sever icing. http://www.pprune.org/ubb/NonCGI/frown.gif

If the incident you refere to was the level burst in the last AAIB bulletin, that was Clear Air Turbulence, (CAT).
We are getting better at forcasting it, and the general areas it is likely to be found can usually be identified. How ever, like a lot of things with the weather, even we "experts" still have a lot to learn, hence why weather research flying takes place. :)

I don't have the link to hand, but try searching on the web for the hurricane hunters of the US Air National Guard and US Airforce Reserve. Going through the eye wall of a hurricane, now that IS turbulence! It surprises many people, that they use bog standard Hercules to do this, with no additional strengthening. ;)

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;-) It looked like a good idea at the time :-)

[PaperTiger]

<font face="Verdana, Arial, Helvetica" size="2">As far as aircraft having been downed by turbulence, this has not happened very often (apart from windshear and such during final approach), but I do remember some accident a few years ago close to the Fuji-yama, when some turboprop aircraft lost some important parts and crashed.</font>

Only one I recall nr Mt.Fuji was the sightseeing BOAC 707 which encountered a mountain wave, was upset and disintegrated.
Not wishing to appear unduly morbid but a number of airliner losses have been attributed to turbulence over the years, although in some cases the cause is more of a guess than anything.
If interested there's a list by cause at:
http://aviation-safety.net/events/wxt.shtml
(includes low-level turbulence/crosswind events as well but excludes windshear).

[This message has been edited by PaperTiger (edited 21 June 2001).]