Nonlinear Aeroelasticity and Flight Dynamics of High-Altitude Long Endurance Aircraft

High-Altitude Long-Endurance (HALE) aircraft have wings with high aspect ratios. During operations of these aircraft, the wings can undergo large de°ec-tions. These large de°ections can change the natural frequencies of the wing which, in turn, can produce noticeable changes in its aeroelastic behavior. This behavior can be accounted for only by using a rigor-ous nonlinear aeroelastic analysis. Results are obtained from such an analysis for aeroelastic behavior as well as overall °ight dynamic characteristics of a complete aircraft model representative of HALE aircraft. When the nonlinear °exibility efiects are taken into account in the calculation of trim and °ight dynamics charac-teristics, the predicted aeroelastic behavior of the com-plete aircraft turns out to be very difierent from what it would be without such efiects. The overall °ight dy-namic characteristics of the aircraft also change due to wing °exibility. For example, the results show that the trim solution as well as the short-period and phugoid modes are afiected by wing °exibility