Identification of rotor flapping equation of motion from flight measurements with the RSRA compound helicopter

The application of an integrated rotorcraft identification method to the linear modeling of rotor system dynamics is studied. Two approaches used to describe the rotor flapping parameters in the rotor state dynamic equations and the period coefficients of the blade flapping equation of motion are presented. In the first approach, the parameters are identified in the nonrotating reference frame; in the second, the blade equivalent damping and spring periodic coefficients as well as other periodic coefficients are identified in the rotating reference frame.