ORIGINAL: imsofaman
It is sufficiant to say that is completely eliminated by the articulation of the rotor blades, which must be overcome in order to control the craft. The Autogiro responds as readily to the controls as the most maneuverable airplane. If gyroscopic effect were produced by the revolution of the rotor, it would be practically impossible to bank the craft for a turn or to bring its nose down or up for a landing.
So....Cierva was saying, due to the coning effect, he was able to bank and land his gyro with full control. Without the coning effect, it was uncontrollable and has the tendency to slice to the side thus were his fist failed attempts. The coning effect is actually the dihedral. You need this...unless you have cyclitic control like your gyro. Then coning is not a good thing. TWO DIFFERENT ANIMALS! Look at the twin rotor gyros....each rotor head is tilted slightly.....the rotors are rigid to the head.....but being that both rotor heads create dihedral, you can turn with a rudder.
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.
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.
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.