Aerodynamic Damping of Vibrating Helicopter Rotors.
Final rept. 11 Jun 70-21 Dec 73,
SOUTHWEST RESEARCH INST SAN ANTONIO TEX
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An experimental and theoretical study of aerodynamic damping of a hingeless helicopter rotor harmonically excited in heave in one of several bending modes is presented. Experimental damping data is given for rotor pitch angles of 0, 1 and 5 degrees. At each pitch angle, damping data is presented for a wide range of the oscillation to rotational frequency ratio, m. Rotor structural damping as a function of rpm is also determined so an accurate measure of aerodynamic contributions to total rotor damping is obtained. Theoretical aerodynamic damping is determined by treating the model rotor as a multi-degree of freedom system wherein the structural and aerodynamic properties of the rotor are treated as a series of finite structural elements and a series of two-dimensional strip theory aerodynamic panels. Modified author abstract