Re: Smoke Trail

From:         Rick Hughes <> (Rick Hughes)
Organization: iiNet Technologies (Perth, Western Australia)
Date:         03 Jul 96 01:23:50 
References:   1
Followups:    1
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In Article <airliners.1996.1078@ohare.Chicago.COM>, (Lars A Ewell) wrote:

>	I recently rode on a United Airlines 737
>(-300 I think) and I noticed something peculiar during
>take-off.  Just prior (approx 3sec) to the front
>wheels leaving the ground, a thin (approx 10cm diameter)
>stream of smoke was emitted from the front of the
>engine (I could only see one engine).  This stream of
>smoke traveled over the top of the wing and then
>back toward the tail of the plane.  It lasted about
>ten seconds.


You've almost certainly seen a vortice coming off the engine cowling
at rotation.  The core of the vortice has a lower pressure than
surrounding air, consequently lower temperature.  With a little
humidity in the air, a vapour trail is formed in the vortice, which is
most likely what you witnessed on both flights.

Rick Hughes
Western Australia