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