Imlanphere
I try not to overstress the theory side, although I do cover it. I find that a demonstration is worth far more, but it does help if it is supported by background knowledge. To a basic student at the beginning of the first sortie I simply sit on the ground and demonstrate that as the cyclic is moved so the disk moves in response.
In ground school I work through as follows (assuming a simple freely hinged system):
Revision of the forces on an airfoil, stressing that if lift exceeds mass then the airfoil will climb.
As the airfoil moves upwards there will be two velocity vectors, forward movement and vertical movement, which can be combined through simple vector addition to create a resultant velocity. This resultant “relative airflow” will reduce the angle of attack until the lift created equals mass at which point a stable state is achieved.
Point out that in a helicopter the blade mass and the centripetal reaction will both oppose lift.
At this point, the process becomes known as “flapping to equality” as the system is free to achieve equality of blade lift over mass and centrifugal reaction. One should not go further until the student is comfortable with the concept that constant angle of attack is achieved around the disk in the hover and constant lift moment at all times.
Discuss a tilted disk and compare with a level disk. Draw a graph of vertical displacement. Note that the points of maximum vertical velocity will occur 90° out of phase with the tilt (very easy on a graph). At the 0, 90, 180 and 270 points add angle of attack and examine the total pitch angle. Note that to achieve a disk tilt the max pitch angle must be applied 90° in advance and so on.
Stress that the rotor is a dynamic environment and these changes happen very quickly. (It is possible to demonstrate this with rapid fore and aft control input on some helicopters but if you have hydraulic actuators or jacks they will attenuate the rapid movements.)
Later I discuss the control rigging required to achieve a 90° advance angle.
Much later if the student enquires I will discuss the damping and torsional forces that can be passed to the blades from the head (I instruct on a rigid head aircraft). However, during basic training it is more important that a student accepts that his inputs will be replicated by the disk and that he should simply select and hold attitudes by looking out at the horizon and adjusting the cyclic position as required.
Hope that helps
Grey Area