Accession Number : AD0775929

Title :   Aerodynamic Damping of Vibrating Helicopter Rotors.

Descriptive Note : Final rept. 11 Jun 70-21 Dec 73,

Corporate Author : SOUTHWEST RESEARCH INST SAN ANTONIO TEX

Personal Author(s) : Bass,R. L. , III ; Johnson,J. E. ; Unruh,J. F.

Report Date : JAN 1974

Pagination or Media Count : 63

Abstract : 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)

Descriptors :   *Helicopters, *Helicopter rotors, Vibration, Damping, Aeroelasticity, Flutter

Subject Categories : Aerodynamics
      Helicopters

Distribution Statement : APPROVED FOR PUBLIC RELEASE