Damage Mitigating on a Large Rotorcraft using Load Alleviating Flight Control Laws

This paper presents a method of reducing fatigue damage to critical components on the main rotor hub of a helicopter through load alleviation in the primary flight control system. The method is demonstrated using a simulation representative of the CH-53E Super Stallion. The components in question were the pushrods, rotor shaft, and the stationary scissor links. The component loads and rate of fatigue damage were correlated with aircraft states which are in turn regulated and tracked by a fly-by-wire control system. Using dynamic inversion control laws with command filter shaping, the accumulated damage to each component is shown to decrease during aggressive maneuvers while causing only a small degradation to the handling qualities.