Effects of Flexibility on Aircraft Dynamic Loads and Structural Optimization

*† ‡ § Flexibility has a significant influence on the dynamic response and subsequent inertial loading of an aircraft. A response simulation of a fully flexible aircraft using inertially coupled equations of motion shows that the results are sensitive to small changes in structural properties like damping factor. These effects are studied through the determination of the analytical sensitivities of the internally coupled system of flight and aerodynamics, structures, and controls, computed by using the direct method of finding the gradients of dynamic stresses with respect to damping factor. In the end it is concluded that, in terms of loads, flexibility plays a significant role in the design optimization, and finding the analytical sensitivities for such kind of model is a rigorous task, which can make an unfeasible optimization problem.