Dynamic Analysis of the Rigid Rotor System

A unified dynamic analysis for the rotor motion of the rigid or nonarticulated rotor system in a hovering state is presented. The dynamic behavior of the rigid rotor as well as that of the conventional rotor is expressed in a simple linearized mathematical form by using complex variables. The available control moment and the necessary phase shift for a given cyclic pitch input are obtained in general formulas and charts. Generally, the control and damping moments of the rigid rotor system increase with the increment of the napping stiffness, but there is a critical stiffness at which the aforementioned moments will be maximum. Optimum napping stiffness may be given so as to avoid unfavorable coupling motion between roll and pitch. It is not always necessary to install the control gyro, because similar stabilizing effect may be obtained by using the proper blade configuration without a special gyro system. The necessary control phase advance is also given to avoid cross control of the rigid rotor system.