ROBUST MULTIVARIABLE CONTROL OF ROTORCRAFT IN FORWARD FLIGHT - IMPACTOF BANDWIDTH ON FATIGUE LIFE

This paper presents the analysis and synthesis of a multivariable cont rol systems for a UH-60 Black Hawk helicopter in forward flight by tak ing the fatigue life of critical components into consideration. In par ticular, this paper investigates the impact of the control system band width on both the handling qualities of the helicopter and the fatigue life of a rotor component control horn. The results of non-linear mod el simulations of on-axis doublets and one maneuver reveals that fatig ue life is very sensitive to the control system bandwidth and the leve l of initial damage. For example, a 45 degrees right turn at 140 knots may cause a 148% increase in fatigue damage in the control horn for o nly a 1.3 radian per second increase in control system bandwidth.