v distortion or breakage of the anti backdrive no back components such as the pawl the pawl shaft the cage or the thrust plate the angular position of the mechanical system is determined from on board encoders and resolvers that are coupled to a system shaft in some embodiments it is advantageous to know the rpm of the system so that the outside noise can be filtered out and a clean signal extracted for analysis if the failure monitoring pertains to a flight control actuator and because vibration monitoring testing requires higher rpms the tests are in certain embodiments conducted on the ground at predetermined maintenance cycles in a preferred embodiment however the microprocessor unit is an integral part of the actuator system and coupled with angular position determining circuitry can be used to analyze the mechanical system during actual use in transient modes however depending on the test frequency it can also be designed as aircraft ground maintenance equipment the secondary load path elements in actuators are sometimes preloaded e g tie rod mounted through the screw shaft of an actuator the preload is necessary in some applications to increase the column buckling stability of the screw shaft under compressive stresses the secondary load path in the case of a tie rod serves the purpose.