To: slowrotor
The Robinson head like those on the Bell machines is underslung to minimize if not eliminate any tendency for the blades to lead and lag. With forward cyclic and with the blades equally coned there is no leading and lagging. However in a maneuvering situation or during gust alleviation the blades will flap about the cone hinge and then there is leading and lagging. Since there is no vertical hinge to permit the leading and lagging the forces are absorbed in spanwise blade bending. These loads are transmitted to the head and from there to the mast, which results in a cyclic twisting of the mast. All of the lead lag loads are transmitted via the cone hinges with resultant elongation of the cone hinge, which is in the form of an ellipse. All of these loads are generated at twice the rotor speed during maneuvering.
