In my rotorcraft module at university, we were told that blades leading/lagging is as a result of blade flapping. To conserve angular momentum, an upward flapped blade (CG moves toward rotor hub) will speed up and hence "lead". A downward flapped blade (CG moves outwards) will slow down and hence "lag". I understand this, however if the lead/lag was as a direct consequence of flapping, then shouldn't their frequencies be the same? In the above image (Shown to us in lecture) you can see that the lagging frequency is roughly 1/5 of the flapping frequency. How is this possible? If the blade lag is a direct consequence of flapping surely this is not possible.
Are there more factors that affect lead/lag? Perhaps cyclic pitch control alters the drag of the blades and hence affects the lead/lag? Or could it be to do with the hinge and any associated damping effects.
A comprehensive explanation would be appreciated.