The purpose of this dissertation is to conduct prognostic analysis on a numerical model of an electrohydraulic actuator - used in aerospace environments - to permit early proactive maintenance on the physical system, beneficial for its lifespan extension. The detailed model of a flapper-nozzle servo valve is used to help identify and analyze possible alterations on the dynamical response by applying several types of commands and faults (single or multiple). The main types of commands used in this study are: a basic ramp command, a chirp command with decrescent amplitude, and a mixed time-history command for prognostic purposes. The faults I examined are backlash and increasing dynamic friction on the actuation jack.