What was found
TAIL ROTOR BLADE CONICAL BEARINGS WERE INSPECTED 96 HOURS PRIOR TO FAILURE WITH NO DEFECTS NOTED. BEARING WEAR AND FAILURE CAUSED TAIL ROTOR DRIVESHAFT TO FLEX AND BOUNCE UNTIL IT BROKE IN HALF SEVERING THE TAIL BOOM. FORTUNATELY, THE AIRCRAFT WAS ON THE GROUND. SUBMITTER RECOMMENDED A THOROUGH INSPECTION AT 100-HOUR INSPECTIONS AND SPECIAL DETAIL TO TAIL ROTOR DURING PRE-FLIGHT INSPECTIONS.