What was found
BLACK STREAKS WERE NOTICED ON THE ENGINE COWLING BY MAINTENANCE PERSONNEL. FOUND THE D. C. GENERATOR TO HAVE PREMATURE BRUSH WEAR, WORN BEYOND LIMITS (NO WEAR MARK REMAINING - 100 PERCENT WORN). RECENT OVERHAUL BY REPAIR STATION. CAUSE OF BRUSH WEAR COULD NOT BE DETERMINED. BRUSH PART NUMBER NOT DETERMINED. SUSPECT DEFECTIVE BRUSH MATERIAL COMPOSITION OR IMPROPER INSTALLATION/MAINTENANCE OVERHAUL PROCEDURE.