What was found
(CAN) WHILE TROUBLESHOOTING MAIN ROTOR SYSTEM FOR CAUSE OF DIFFICULTY WITH M/R TRACK AND BALANCE A HAIRLINE CRACK WAS DISCOVERED IN THE DISCREPANT BLADE LEADING EDGE ABRASION STRIP APPROXIMATELY 77 INCHES FROM THE BLADE TIP. THE BLADE AS PLACED ON A WORK STAND AND GENTLY FLEXED UP AND DOWN INDICATING THAT THE CRACK OPENED AND CLOSED WHEN FLEXED. THE CRACK WAS SO FINE IT HAD TO BE VERIFIED WITH A 10X MAGNIFYING GLASS AND THE BLADE FLEXED TO BE SURE IT WAS NOT JUST A SURFACE SCRATCH. THE BLADE WAS REMOVED FROM SERVICE AND REPLACED WITH A RECONDITIONED UNIT SUPPLIED BY BELL. MALFUNCTION REPORT ALSO SUBMITTED TO BELL HELICOPTER.