Dave said, "In a very rigid coaxial or intermeshing helicopter, the tendency for a small roll to the left will be offset by a tendency for an equal roll to the right."
The intermeshing configuration would create a system that has zero angular momentum. If you lift the tail, you're creating a moment to pitch the nose down, add that to the existing angular momentum (0) and the result is that the nose pitches down. A different way of coming to the same result, but I find this one easier to accept.
"Virtually all the inputs are aerodynamic...."
Do those high school physics experiments with spinning things. Sitting on a bar stool with a bicycle wheel, etc. All the energy and inputs into those experiments come from human muscle power. Following your "aerodynamic...is the preferred method" argument, then those aren't demonstrations of gyroscopic effects, rather demonstrations of physiological effects.
I have no problem dropping the word gyroscope (or any related forms). I would really like the word precession dropped (it's wrong to use it).
I think a purely aerodynamic explanation of why rotors behave the way they do works if you also talk about some basic physics.
For example, you can track a stationary rotor blade up and down sinusoidally using a wind tunnel and sinusoidal pitch changes. Problem with this is, as the blade rises to it's maximum flap, you must use blade pitch to actually decelerate the flapping motion. You stabilize with the blade pitch and flapping position to be 180 degrees out of phase (ie minimum pitch at maximum flap).
You then realize that the blade doesn't have a restoring force to return it to it's median position. You set up a spring or pendulum as a restoring force, run the experiement, and find that if you're not too aggressive with the amount of pitch change, you get approximately a 90 degree phase angle.
Since the turning blade has a restoring force, this seems to support an aerodynamics only explanation. Problem is the restoring force on the helicopter is centrifugal force (aarrrgghh...I hate that term). In order for this to work, you need to use some rotational dynamics.
With a restoring force and the flapping motion of the blade, the blade looks like a pendulum, swinging about the flapping hinge. If the flapping frequency is the same as the rotor speed, then the phase angle should be 90 degrees. Flapping frequency depends on mass distribution and apparently many aerodynamic things (density, chord, lift curve slope...from Kyrilian's ref to the Lock number).
This may not be the aerodynamic precession that you refer to, but every time I think I understand an aerodynamics only explanation, I find something that requires rotational dynamics.
I would tend to go along with Gareth D. Padfield (except for using the word, "gyroscopic"). Rotors do generate aerodynamic forces, but unlike fixed wing aerodynamics, some sort of spinning physics is critical.
Matthew.