A preliminary theoretical flutter analysis of the JS1 glider

Abstract

A preliminary theoretic flutter analysis of the new JS1 18m-class glider was performed by means of analytic methods. This analysis consisted of a detailed modal analysis using finite element modelling followed by the flutter prediction. The modal analysis was computed with the aid of the commercial FE-code ANSYS in which a model of the complete glider was generated. This model was created in such a way as to effectively simulate the composite characteristics, while also ensuring that the results were easily extractable for flutter prediction input. By using the Block-Lanczos method, the 1st, 2nd, and 3rd main wing bending and torsion modes as well as the T-tail configuration modes were all extracted in the frequency range from 0 - 30 Hz. These modal results, which included the natural frequencies, mode shapes and displacements were then used as the input for the flutter code. The flutter prediction was done with the software code SAF (Subsonic Aerodynamic Flutter). This prediction made use of a complete panel model for the glider, while the flutter algorithm was solved with the p-k method. The flutter results, in the form of V-g and V-f graphs, all showed main mode stability over the entire velocity range of 1.2V, up to an altitude of 25000 ft.