  Current flight control validation is heavily based on linear analysis and
high fidelity, nonlinear simulations. Continuing developments of nonlinear
analysis tools for flight control has greatly enhanced the validation process.
Many analysis tools are reliant on assuming the analytical flight dynamics but
this paper proposes an approach using only simulation data. First, this paper
presents improvements to a method for estimating the region of attraction (ROA)
of nonlinear systems governed by ordinary differential equations (ODEs) based
only on trajectory measurements. Faster and more accurate convergence to the
true ROA results. These improvements make the proposed algorithm feasible in
higher-dimensional and more complex systems. Next, these tools are used to
analyze the four-state longitudinal dynamics of NASA's Generic Transport Model
(GTM) aircraft. A piecewise polynomial model of the GTM is used to simulate
trajectories and the developed analysis tools are used to estimate the ROA
around a trim condition based only on this trajectory data. Finally, the
algorithm presented is extended to estimate the ROA of finitely many
equilibrium point systems and of general equilibrium set (arbitrary equilibrium
points and limit cycles) systems.
