As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A ROUTINE TAILROTOR GEARBOX CHANGE, WHILE COMPLETING THE TAILROTOR BALANCING PROCEDURES. AFTER MX OBTAINED THE VIBRATION READING AT 100 PERCENT, THE PILOT DECELERATED THE ACFT TO FLIGHT IDLE AND APPROX 10 SECONDS INTO THE COOL DOWN PROCEDURES (AT FLIGHT IDLE) THE NR 2 TAILROTOR SEGEMENTED DRIVESHAFT FAILED AT THE CENTER OF THE DRIVESHAFT.