Mxsmanic wrote in
news
Snowbird writes:

I guess Mxmanic uses the FAA AIM as his main source in his
"research".

That is only one of many sources. They all say the same thing.

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.

The wakes of smaller aircraft descend as well.

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.

Including myself.

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

Yes. Although the downwash itself should be strongest when the
aircraft is dirty and slow. The reason clean and slow produces
stronger _vortices_ is that it only produces one pair, whereas flaps
and other control surfaces can produce multiple vortices of smaller
size that tend to interfere with each other and reduce overall
turbulence.

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).

Which makes it all the more difficult to understand how a pilot could
feel his own wake in a level 360-degree turn.

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?

You're neglecting the downwash, which is present in all aircraft.
Downwash tends to pull all turbulence behind the aircraft down with
it.


No, it doesn't, fjukkwit. Only most of it.

Send me fifty bucks and I'll explain why to you


bertie