ORIGINAL: John235
Where in the quote did Cierva refer to the coning of the autogyro? It appears to me that the quote refers to the use of flapping hinges, rather than coning. I haven't read Cierva's book, but I believe the flapping hinges were required to solve the problem of lift dissymmetry, not to deliberately increase coning.
He didn't. We hashed this to death on RCGroups. Coning has no advantages. It doesn't provide yaw/roll coupling, nor does it
create any stability laterally or longitudinally.
ORIGINAL: John235
My view of this issue is that flapping hinges have several advantages. Mainly it works as a type of stabiliser to regulate the dissymmetry of lift. Dissymmetry of lift can be solved with cyclic controls but I believe that some form of blade articulation (flexible blades, flapping hinge, head damping or teeter hinge etc) is still needed to for reasons such as stability, to reduce vibrations, and to reduce the control forces. I don't think there is really any dispute about these benefits.
This is all true, and as you point out it has nothing to do with coning.
ORIGINAL: John235
The advantages of coning is where the disagreement seems to be. There are obviously some disadvantages, but there may also be advantages. One thing that is totally clear to me is that coning does not provide yaw-to-roll coupling in the same way that dihedral does on model aircraft without ailerons. The question in my mind is how coning affects longitudinal and lateral stability of rotorcraft. It occurs to me that coning will increase stability on these two axis, which is similar to the use of dihedral to increase lateral stability on full size aircraft. I think its possible that stability provided by coning could be a help with model autogyros that do not use cyclic control. I expect the mechanism for yaw-to-roll coupling in autogyros without cyclic control has a more involved explaination than what I would consider as common sense.
The disagreement is from those that don't understand how dihedral works on an airplane in the first place and that it works
by virtue of yaw/roll coupling. Since the yaw/roll coupling on a rotor is 90 degrees out of phase it can't possibly work like
dihedral.