Aeroelastic stability analysis of the FLEXOP demonstrator using the continuous time unsteady vortex lattice method

Abstract

This paper introduces a new assessment method for static and dynamic aeroelastic stability of free flying flexible aircraft in which the aerodynamic model is based on a continuous time state space formulation of the unsteady vortex lattice method. By the integration with the structural and flight dynamic equations of motion, the resulting aeroelastic time domain model is obtained. With utilizing the flight velocity as scheduling variable, a parameter varying state space model is formulated making efficient stability analysis possible. In order to validate the proposed method, aeroelastic stability analyses are carried out on the example of the FLEXOP demonstrator aircraft. Comparisons are made with calculations run with the commercial software package Nastran. Advantages of the proposed method are demonstrated by the analysis of effects whose consideration is not or only partly possible with other state of the art methods. Those effects include (i) steady wing loading at the point of linearization; (ii) static deformation due to steady wing loading at the point of linearization; and (iii) twist and camber distribution.