"Rip" wrote ...

Oh well. The entire thread has forced me to ask myself just what the wake
behind an aircraft looks like. Like every other pilot, I know you can
intercept your own wake during a constant altitude turn, but it would be
neat to be able to SEE all of the air masses at work.

Thanks for your smoke insights ;-)
There are some great photos depicting the tip vortices he
http://www.airliners.net/open.file/1091105/M/
http://www.airliners.net/open.file/1008033/M/

Here are some real masterpieces :

http://www.airtoair.net/gallery/gallery-vortices.htm


I guess Mxmanic uses the FAA AIM as his main source in his "research".
Section 7.3.1 is about wake turbulence. A couple of interesting quotes from
that section, that Mx has not seen fit to share with us:

a) "Flight tests have shown that the vortices from larger (transport
category) aircraft sink at a rate of several hundred feet per minute,
slowing their descent and diminishing in strength with time and distance
behind the generating aircraft."

Note the explicit reference to large aircraft. In fact, it seems all actual
wake turbulence safety studies have involved large aircraft, i.e. B707 and
larger. This is in fact quite natural, as there was no real safety issue
before the large jetliners appeared.
b) "Test data have shown that vortices can rise with the air mass in which
they are embedded."

There you are, official proof to the statements of several of our
contributors.

c) "The greatest vortex strength occurs when the generating aircraft is
HEAVY, CLEAN, and SLOW."

In contrast, a light aircraft doing a 360 is usually LIGHT, CLEAN and
(relatively speaking) FAST. Very different conditions, especially regarding
two major sources of wake: the AoA of the wing (which affects the tip
vortices) and the power setting (which affects the propwash strength).

The interesting study question here, for the light airplane case, would be
the relation between the tip vortices (which presumably sink, as for large
aircraft) and the propwash (which is basically horizontal). I think glider
pilots can testify that the propwash is the dominant one, at least close
behind the tug airplane - any soarers out there who can comment?

But realistically, as the wake behind a light aircraft is no real safety
hazard, there is no compelling reason to study this case. So unless someone
can produce a reference, let's rely on the observational data from countless
pilots.