As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) MAIN ROTOR BLADE ABRASION STRIP SEPARATED FROM BLADE WHILE IN FLIGHT. VIBRATION CAUSED BY IMBALANCED ROTOR DISK REQUIRED RETURN TO BASE. ACFT WAS SHUTDOWN. NO FURTHER DAMAGE TO ACFT NOTED. REMAINING 4 ROTOR BLADES HAVE SAME HRS FLOWN AND HAVE BEEN REMOVED FROM SERVICE PENDING INVESTIGATION MFG HAS BEEN NOTIFIED.