Originally Posted by
IFMU
The problem with the rigid rotor is dissymmetry of lift. Juan de la Cierva figured this out.
https://en.m.wikipedia.org/wiki/Juan_de_la_Cierva
So can you crank in enough cyclic pitch to overcome this dissymmetry? Let's say you could. For a US rotation helicopter you need a bunch of right cyclic as you start going forward. But if you allow a bunch of left cyclic you give a tool to the pilot to get in a lot of trouble. And then what about sideward and rearward flight? I guess the pilot needs some of that addional travel to account for it. But how do you limit his authority in the down flap direction when he changes mode of flight?
Flapping does all this for us and it works as a bias summed with the collective control. The stick does move laterally with airspeed but not really all that much that we can't live with it.
Obviously discap was not asking about a truly rigid rotor but rather about a hingeless head. All the issues you are explaining are solved on hingeless systems, such as the 105. Now the question remains why this hasn't been realized with a two blade system yet. I've been asking myself the same question and so far I don't see any convincing answers on this thread. I may be wrong but I suspect that helicopter designs have been evolving towards higher number of blades solely due to the obvious reasons, not because of the elimination of the hinges.
For example the evolution from 212 to 412, I don't think they put on the two extra blades because they wanted to go hingeless. They probably wanted to develop an overall more modern rotor system, with all its benefits (if these elastomeric bearings were such a good idea is a different question).