Re: Three questions.

From: (romina)
Organization: Centro Servizi Interbusiness
Date:         27 Jun 96 12:42:10 
References:   1
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Peter Smooker <> wrote:

>3. An Evergreen cargo 747 (200?) was about to take off. There was
>substantial vapour coming from the left wingtip. It took off and the
>vapour increased. After takeoff vapour was coming from the right hand
>wingtip as well, obscuring the plane. Was this fuel, and if so, is it not
>dangerous? Why was it being released?

>Thanks for the explanations

About your 3rd question
Vapour is actually normal at wing tips during rotation, especially
during humid days. It is condensed water (contained in the air in
gaseous state at ambient pressure). Water contained in the air always
condenses when pressure decrease, as the saturated value (water/air
ratio) is reached for that temperature. The pressure strongly decrease
at wing tips during rotation as result of strong wing tip vortex due
to difference of pressure between upper and lower surface of the wing.
Sorry for my weak English. Hope to have clarified the nature of the
phenomen. Andrea