Re: Smoke Trail

From: (Ricky Scott)
Organization: The Boeing Company
Date:         03 Jul 96 01:23:49 
References:   1
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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.  The sight reminded me of pictures I have
: seen of objects being tested in a wind tunnel where smoke
: (or something similar) is used to make visible the
: airflow direction.  The same scenario was repeated on
: my return flight.

: 	Has anyone else seen a similar phenomena?  More
: specifically, does anyone know what the cause of this
: is?

: 	Lars Ewell

Lars,  Well what you saw was not smoke but acutally a vortici of super
cooled air comming off the tip of the engine strut. I have flown on
several types of aircraft and have seen it off of flaps, wing tips
engines and all manner of pieces and parts.  I bet if you think back it
was a really cloudy or rainy day. It happens when the air is humid (full
of moisture) and as the speed increases over the part it induces a
vortex.  This in turn super cools the air causing it to become visible
(Clouds) ... that is what you saw.  The angle of the take off from about
rotation to when they achieve climb angle is just right to cause a vortex
to form off the small hole/intake on the engine strut of the 737.  Look
out on the wingtips some day when its cloudy/humid and you will most
likely see the same thing.

Hope that helps (I tried to keep it in laymans term)

Ricky J. Scott

I dont speak for my company and they do not speak for me
We like it that way and so do their Lawyers.