As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING T/O, BANG HEARD BY PILOT, ABORTED T/O. CONFIRMED SUSPECTED SPRAG FAILURE DIAGNOSIS WITH HELICOPTERS AND PILOTS REPORTED SYMPTOMS. CLUTCH ASSY REPLACED IN FIELD. DIAGNOSIS FURTHER CONFIRMED BY DIASSASEMBLY OF RETURNED SPRAG UNIT BY MFG.