Dave wrote:
This the best explanation I have seen yet..

I have tried it, 1974 172 m, 40 deg., all the rudder we had,
....

You have to work a little harder than that. The phenomenon you were
looking for depends a lot on the CG. Many years ago when I used to fly
Cessnas of various vintage, I discovered the phenomenon after much
trial and error. It was most likely to occur near the rear CG limit in
a (early '70s)172 near gross. Frankly, I don't know what all the fuss
was about. It produced a fairly mild pitch oscilation that I couldn't
distiguish from the usual convective turbulence we get here in the
desert. If it wasn't for the instructor in the back seat pointing it
out, I would have missed it.

John Galban=====N4BQ (PA28-180, slips with flaps and got the T-shirt!)