[quote=Arm out the window;2907760]
You guys seem to be considering the CofG as the pivot point around which everything happens, whereas I'm looking at it simply as the point through which the weight of the helicopter can be said to act, and in that regard it's just another point at which force is being applied to the whole combination.
quote]
Arm, you are right that the A/C CoG is the point at which the total weight of the helicopter acts through, and it also is the pivot around which everything happens. The CoG is not a fixed point but it acts as one due to inertia. But you have to keep in mind that there are quite a lot of 'sub' CoG's. For instance the CoG of the rotor system, or a single blade. It is, however, impossible to consider all the forces acting on a flying helicopter to clarify it in a single two dimensional picture.
Coming back to the inertia around the CoG; consider the following:
Measuring the unbalance of the Main rotor is done with an accelero or veloci meter device. Why do we measure it in the lateral plane? The out of center CoG of the rotor system produces a moment to the A/C CoG. This moment is equally proportional around the mast centre. However the amplitude in the lateral plane is larger than the amplitude in the longitudinal plane, and this is a result from the fact that obviously the inertia of the complete body is higher in the longitudinal plane.
cheers,
YB