THE RESPONSE OF HELICOPTER ROTORS TO OSCILLATORY ROTOR PLANE DRAG FORCES AT THE BLADES

摘要

A theoretical analysis is given for the response of an elastically restrained rotor having drag hinges to a harmonic force (in the rotor plane) acting on each blade. The purpose of the analysis is to lead to a method of providing the helicopter dynamics engineer with means of controlling flight vibration characteristics. Results are presented in the form of equations from which hub displacement and resonant frequency expressions are derived for simplified conditions. The cases treated are those in which the ratio of hub elastic restraint in one direction to that in the orthogonal direction is zero, one, and infinite. A numerical example is worked out for each case, with a combination of known and assumed parameters which is typical of a medium size helicopter. The results are presented in the form of graphs which show variation of hub response as a function of change in hub restraint.