Influence of control on flexible aircraft crack growth

The overall objective of this research is to investigate and assess the leverage generated by flight control loops for reducing fatigue damage and enhancing structural integrity. An analytical state space crack growth model is briefly considered first. Next, a dynamic flexible aircraft model is presented. Stress response from the aircraft is applied as input to the crack model. Design of a flight control system is also considered. Objectives of the controller are to correct deficiencies in the vehicle motion. Comparison of open-loop and closed-loop stress responses indicate the control system has substantial effect on transient stress behavior. Long-term fatigue damage and structural integrity predictions, and the influence feedback control and load have on such predictions, are made with simulation runs. A mix of open-loop and closed-loop cases with nominal and variable feedback gains, and vehicle motions including nominal maneuvers and overloads are used. Individual feedback gain values have substantial influence on crack growth