What was found
DURING ROUTINE 500 HOUR INSPECTION THE PULLEY SPINDLE ON WHICH THE INNER RACE OF THE BEARING IS PRESS FIT WAS FOUND VERY WORN WITH MORE THAN 10" OF THE PROPER SPINDLE DIAMETER WORN AWAY AND SOME CORRESPONDING WEAR ON THE BEARING INNER RACE AND WEAR ON THE HYDRAULIC PUMP DRIVE PULLEYS SPLINED COUPLING SLEEVE. THIS IS THE THIRD INSTANCE OF WHICH WE ARE AWARE OF THIS DEFECT OCCURRING. THE BEARING ITSELF HAD NO APPARENT ROUGHNESS WHEN TURNED BY HAND. SUSPECT SOME PULLEYS OR PERHAPS BEARINGS HAVE BEEN IMPROPERLY MACHINED, DIAMETERS WHICH ALLOW THE INITIAL SLIPPAGE AND SUBSEQUENT CHATTERING DEVELOPS WHICH REMOVES MATERIAL OVER TIME. THIS HAPPENED BETWEEN INSPECTIONS. BELT TENSION MUST BE RELEASED TO DETECT THIS DEFECT AS THE BELT AND THE COUPLING SLEEVE. HELP KEEP THE PULLEY ALIGNED DURING A CURSORY INSPECTION OR WHEN THE AIRCRAFT IS OPERATING. WE INSPECT FOR THIS EACH 100 HOURS.