What was found
AC WAS CLIMBING TO ALTITUDE, SEVERE CLEAR AIR TURBULENCE WAS ENCOUNTERED. THE LEFT GEN. TRIPPED OFF LINE. THE GEN. WAS RESET AND STAYED ON LINE FOR ABOUT 10 MIN. THEN TRIPPED AGAIN. DECISION WAS MADE TO COMPELTE TRIP WITH ONE GEN. WHEN LOWER COWLING WAS REMOVED, SMALL PIECES OF STARTER BRUSH LAYING IN THE BOTTOM. THE BRUSH COVER WAS REMOVED AND SEVERAL PIGTAIL RETAINING RIVETS AND PIECES OF BRUSH ALSO CAME OUT. ONE BRUSH WAS MOSTLY GONE. SEVERAL PIGTAILS HAD SIGNS OF MELTING AND SEPARATING FROM THE BRUSH. REMAINING BRUSHES INDICATED THERE WAS STILL WEAR LEFT TO GO TO OVERHAUL. ARMATURE WOULD TURN BY HAND, EVEN WITH SPRING TENSION ON BRUSHES. INSTALLED OH STARTER, OPS CK OK.