Stability of Very Flexible Aircraft with Coupled Nonlinear Aeroelasticity and Flight Dynamics

Abstract

This paper presents a framework for analyzing the stability characteristics of a very flexible aircraft, simultaneously taking into account nonlinear aeroelasticity and flight dynamics. Here, the dynamics formulation is deduced by combining the displacement-based geometric nonlinear finite element method with the nonplanar panel method, and it is linearized carefully around the trim configuration with large static deformations. A mean axis system, the origin of which is at the center of mass of the aircraft trim configuration, is used to eliminate the inertial coupling. The methodology in this paper generalizes the conventional linear analytical method to deal with stability problems of nonlinear systems and can be easily integrated into the industry design process and complex structures. The numerical results for a very flexible flying wing indicate the necessity to consider aeroelasticity and flight dynamics integrally, because the gap between the frequencies of rigid-body motions and elastic modes tends to be narrower and the coupling effects may worsen the envelope.