Aircraft hydraulic systems are used to actuate flight control surfaces, thrust vectoring and reversing mechanisms, landing gear, cargo doors, and in some cases, weapon systems. The hydraulic pump and motors are widely recognized to be the most critical component within the system. To monitor critical hydraulic pumps and motors, a diagnostics process was developed and programmed on a prototype online health monitor. The approach includes performance modeling; signal processing and feature

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... ion; feature level fusion; automated classification; and knowledge fusion for estimating degradation through the collection of in-line pump sensor data. The methods employed and an initial hardware and software realization are reviewed. The effects and tracking of pump wear and fatigue damage as witnessed from a series of endurance tests conducted at the Air Force Research Laboratory (AFRL) are shown from the successful results of stimulating the in-line pump with digitized test data.