Active interrogation of helicopter rotor faults using trailing-edge flaps

This paper describes a unique approach for detecting helicopter rotor faults in which active trailing edge flaps are used to interrogate the system. The objective of the research are to determine if active interrogation of helicopter rotor systems using trailing-edge flap actuators is a viable concept and to develop damage identification algorithms that are appropriate for active interrogation. Using this concept, the blade is excited by a low amplitude trailing edge flap deflection at a few discrete frequencies. The blade response is measured using embedded strain sensors and the health of the system is determined using a frequency response function based damage identification algorithm. Evaluation of the design is performed using a numerical simulation of a rotor system, which includes centrifugal forces, aerodynamic forces, and high aerodynamic damping. Good results are shown for detection and extent quantification of both stiffness and inertial faults. Ongoing work includes a strain-based implementation, investigation of additional faults, effects of noise and error, and analysis of the minimum size of detectable faults. Benefits of this work include both improved health monitoring for rotorcraft as well as insights into the application of structural damage detection algorithms to a complex system.