Aeroelastic modelling of the Sonaca 200

Abstract

The present work concerns flutter analysis of the Sonaca 200, more precisely extension of the aeroelastic model to the full airplane. It fits in the continuation of two master theses that studied aeroelastic behavior of the main wing. The studied configuration corresponds to the prototype state of the airplane in 2018, without fuel nor luggage and with fixed control surfaces. An analytical approach relying on Megson aircraft structures theory [1] is here implemented to provide structural models for the rear fuselage and the empennage that are suited for flutter analysis. The different components are then assembled using elastic connections to create a full finite element model of the aircraft. Numerical modal analysis is performed on this latter and the resulting eigenmodes are compared with experimental data from ground vibration testing for validation. In parallel, an aeroelastic model of the Sonaca 200 utilizing the vortex lattice theory [2][3] is developed in Matlab based on the work of Dimitriadis. It manages aerodynamic efforts on the structure with use of vortex ring elements and relies on modal analysis data to solve the aeroelastic equation of motion. The algorithm is first tested with experimental modes and provides a satifactory degree of comparison with reference aeroelastic solutions computed by the Leichtwerk company. Outputs of the finite element model are subsequently injected in the program to observe the differences in terms of aeroelastic solutions. The results seem encouraging but highlight sensitivity of the Vortex Lattice Method to modal parameters of the system. It would thus be beneficial to investigate ways of improving accuracy of the finite element model for it to be appropriate in practice. Part of this improvement may come from determination of the real boundary conditions with the ground. Besides, implementing movable control surface in the finite element model would allow to test critical configurations of the airplane where actual flutter might appear.