Acer V wrote:
>
> Could it also be water vaporization? Above the wing, air pressure is
> lower, so water "boils" at a lower temp, etc. Did that make sense? I've
> seen these "trails" lots of time and enjoyed the sight as well. If I
> recall, most of them ocurred when descending thru cloud layers for landing
> approach. Anyone?
Water in the air, unless it is rain, clouds, or fog, is in the vapor
form. If it suddenly becomes visible it is due to condensation. If you
watch high speed aircraft making a sharp turn you can see water
condesation at the wing tips outlining the wing tip vortices as a kind
of vapor trail. The phenomenon described sounds more like a sudden
change in the refractive index of the air over the wing such as might
occur at a supersonic transition boundry or the place where laminar flow
changes abruptly to turbulent flow. I believe it is the latter
phenomenon as it occurs over the top of the wing about a third or more
back from the leading edge where turbulent flow is expected to begin.
Jerry Liles
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