Control Equivalent Turbulence Input Models for Rotorcraft in Hover and Forward Flight

Abstract

The paper focuses on the development of turbulence models using the Control Equivalent Turbulence Input method, i.e. the determination of control inputs required to generate aircraft angular and vertical rates in calm conditions that are consistent with rates observed when flying in atmospheric turbulence. For the extraction process, this method uses a mathematical model of the aircraft dynamics and aircraft angular and vertical rates measured during flight tests in turbulence. Analyzing and modeling the power spectral densities of the extracted control disturbances allows to generate low order equivalent turbulence models that can be used for control system optimization, handling qualities investigations, and pilot training. This method has successfully been used for hover and low speed flight in the past and is now extended to forward flight. The paper describes the flight tests conducted in turbulent conditions, the extraction of the equivalent control input traces and their power spectral densities, and the determination of the desired turbulence models. The paper also presents validation of the derived turbulence models.