Flight Dynamics of Highly Flexible Flying Wings

The paper presents a theory for flight dynamic analysis of highly flexible flying wing configurations. The analysis takes into account large aircraft motion coupled with geometrically nonlinear structural deformation subject only to a restriction to small strain. A large motion aerodynamic loads model is integrated into the analysis. The analysis can be used for complete aircraft analysis including trim, stability analysis linearized about the trimmed-state, and nonlinear simulation. Results are generated for a typical highaspect-ratio “flying wing” configuration. The results indicate that the aircraft undergoes large deformation during trim. The flight dynamic characteristics of the deformed aircraft are completely different as compared to a rigid aircraft. For the example aircraft, the phugoid mode is unstable and the classical short-period mode does not exist. Furthermore, nonlinear flight simulation of the aircraft indicates that the phugoid instability leads to catastrophic consequences.