this is an excerpt from a letter written by Ray Prouty:
"...If you are on the ground and apply maximum cyclic pitch to the rotor when it is over the nose, the tip path plane will tilt up 90 degrees later on the left side (and down on the right) following the laws that apply to a gyroscope.
If you are in the air, the same thing happens as you call for an acceleration of a right roll by applying maximum pitch over the nose. (If the rotor has offset flapping hinges, the angle is not 90 degrees, but something less--maybe 85 degrees). However, once you achieve some rate of right roll, the situation changes and the tip path plane will not be responding at 90 degrees, but at some smaller angle depending on the design of the blades. This angle can be as low as 60 degrees depending on the design of the blades and results in rate crosscoupling.
Some helicopter designers arrange the cyclic control system such that a stick movement directly to the right produces maximum pitch over the nose and rely on the pilot to take care of the rate cross-coupling. Others, such as Robinson, rotate the controls to minimize this crosscoupling while accepting some acceleration crosscoupling.
There are some other sources of crosscoupling, so one value of control phasing will never be optimum....."
I typed this out because it was unfair of me to use Ray's name in the above post along with other information which was not given by him.
[This message has been edited by lmlanphere (edited 14 December 2000).]