COMPARISON BETWEEN EXPERIMENTAL AND PREDICTED ISOLATED HELICOPTER ROTOR TRANSFER FUNCTIONS FOR UNSTEADY INPUTS ON THE CONTROLS

Brite Euram project BE-95-1311 HELIFLOW includes investigations into specific problems of helicopter flight mechanics. Task no. 6 of that project is dedicated to the measurement and prediction of isolated helicopter rotor dynamic transfer functions for different configurations (advance ratio, lift). Tests were performed in ONERA S1MA wind tunnel in December 1997 and code validations were performed by the partners participating in this task by comparisons between wind tunnel test results and computed results. This document recalls the general purpose of the tests, describes the codes used for comparisons with the experimental results and highlights the influence of taking non linear effects, blade deformations and vortex wake into account. An identification method based on an error minimisation technique in the frequency domain has also been used in order to obtain a parametric model built from stability and control derivatives; results concerning this approach are also presented. This work was supported by the EUROPEAN UNION under the Brite Euram programme.