Jet condensation trails

[Khandro]

If condensation trails from jet airliners are the product of water vapour entering a cold environment, why yesterday, planes travelling south towards Switzerland against a clear blue sky did not produce any. Could it be that the air temperature was high due to a Foehn wind?

[Khandro]

^^ It seems they sometimes do; http://science.howstu...el-before-landing.htm

[Euphemia]

To digress, when I lived in Switzerland, I suffered terrible headaches when the Foehn was blowing

[Bazile]

It sound dangerous to me - ( although i knew that it happened ) but it cant be if it is done .

I just imagine the fuel / fuel vapour being sucked into the engine , when the dumping occurs , if for example there is a strong wind ?

[237SJ]

They dump fuel when the aircraft has taken off for somewhere and has to return to the airfield with a problem (or divert). It comes out of valves on the wing and sprays out into the atmosphere. It can take quite a long time to empty a 747 for something like LHR-SIN. If they didn`t do it, the aircraft would be too heavy to land.

[Bazile]

//..I'm a fan of air crash investigation on national geographic chanel ..//

M3rm4n - me too ,I thought i was unsual :-)