aeroplanes

[northboy]

on a clear day and u look up to the sky what exactly is it that the plane extracts from its jet engines to make a path of white smoke.
is there a word for it.

[Buenchico]

Any aircraft which has 'smoke' (of any colour) coming from its engines is probably in big trouble! ;-)

'Contrails' are simply artificial clouds, created by nothing more than water. See here:
http://en.wikipedia.org/wiki/Contrail

Chris

[Clanad]

As usual, Chris is exactly right... however with a pedantic caveat. Older jet aircraft that are still in use such a McDonnell Douglas DC-9's and the earlier Boeing 737's (Model 100, 200 and 300's) used the Pratt and Whitney JT8D in its various configurations and it was (and still is) quite "smoky". Viewed against a cloudy sky the exhaust can easily be seen. Any contrails from these aircraft are, nevertheless, only water vapor.
Newer P&W engines, as well as GE, GE/SNECMA and Rolls Royce engines are much cleaner and more fuel efficient...

[northboy]

thank you that was the word i was looking for.
what a very knowledgeable person you are.
i have noticed that you do answer a lot of stuff on here.

[Buenchico]

Thanks for the acknowledgement, Northboy. I suspect that you were typing while Clanad was posting. I have to accept that he's the real expert when it comes to aircraft - he's a commercial pilot ;-)

Clanad: It's good to see you posting on your specialist subject again. You've recently posted so many helpful replies in 'Food & Drink' that I though you were thinking of giving up flying and opening a restaurant ;-)

Chris

[Clanad]

Likewise, Chris... I see your posts in many different sections, but you are especially knowledgeable about things aviation. No plans for a gastronomic endeavor, but somehow we've managed to pick up some unique recipes... Good to see you1