• An aeroelastic framework for very flexible aircraft (VFA) is developed using geometrically exact beam theory and unsteady aerodynamics. • Flutter behavior is analyzed across three modeling fidelities, revealing the importance of accounting for full-aircraft dynamics. • High wing pre-curvature deteriorates flutter margins but increases the endurance factor, and thus must be optimized. Very flexible aircraft (VFA) have emerged in aviation in response to the objective of maximizing flight efficiency, particularly in high-altitude, long-endurance missions. However, their reduced stiffness often brings about harmful effects, such as a reduction in flutter speed. This paper explores a proposed strategy to mitigate the impact of structural flexibility on the degraded flutter behavior of a typical VFA model: the application of a downward bending pre-curvature to the wing. A low-order, geometrically exact beam finite element model is coupled with an unsteady aerodynamic formulation via strip theory to form an aeroelastic framework capable of simulating full-aircraft free-flight dynamics. Motivated by prior studies that suggested pre-curvature could mitigate flutter onset in constrained wings, this study extends the analysis to a trimmed, free-flying configuration. Three modeling fidelity levels are compared: a cantilevered wing at zero pitch, a cantilevered wing in trim-matched conditions, and the full aircraft in free flight. Results show that while moderate downward pre-curvature can slightly raise the flutter speed, the effect is sensitive to the interaction between structural deformation and rigid-body motion, and analyses limited to the wing alone fail to capture this behavior. The findings underscore the importance of whole aircraft modeling for reliable stability prediction in VFA and suggest that wing pre-curvature can be optimized in multidisciplinary design processes to balance aerodynamic performance and aeroelastic robustness.
Santos et al. (Sat,) studied this question.