Abstract
This paper investigates the coupled aeroelastic and flight dynamics stability of flexible lightweight aircraft. The aerodynamics are modelled by the discrete-time unsteady vortex lattice method, which can capture the large deformations of the lifting surfaces, and includes 3-D effects and in-plane motions. A geometrically-exact composite beam formulation is used to model the nonlinear flexible-body dynamics, including rigid-body motions, and the equations are accommodated to discrete-time formulation. The governing equations are linearised around an equilibrium configuration, which can be highly deformed, performing a small perturbation analysis and assuming a frozen aerodynamic geometry. The resulting framework is a monolithic discrete-time state-space formulation, which provides a powerful tool for the stability boundary prediction of a flexible vehicle through a direct generalized eigenvalue analysis. It offers increased fidelity as compared to traditional tools, and at very low computational cost. As a suitable test case to illustrate the capabilities of this approach, the flutter of a T-tail is examined. In addition, previous open-loop results are extended in order to asses wake interference effects on flexible aircraft dynamics.