Evaluation of Control Equivalent Turbulence Input (CETI) Models for Hover and Forward Flight

Abstract

This paper details developments in Control Equivalent Turbulence (CETI) Input models. Using these models, control inputs are calculated that generate aircraft angular and vertical rates in calm conditions equivalent to those when flying in atmospheric turbulence. In this paper, previous efforts to generate CETI models for the EC135 in hover are extended to include dependency with respect to forward flight speed and flight altitude. 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. This is performed through piloted simulation trials conducted in the Air Vehicle Simulator (AVES) at DLR. Results showed the appropriateness of developed CETI models to simulate atmospheric turbulence over the flight envelope.