What was found
MAIN ROTOR DRIVESHAFT (INPUT DRIVESHAFT) SHEARED AT THE FLANGE ON THE TRANSMISSION FLEX COUPLING GEAR, AT THE TRANSMISSION END OF SHAFT. THE FAILURE OCCURRED IN NORMAL CRUISE FLIGHT. AUTOROTATION LANDING MADE WITH NO DAMAGE TO AIRCRAFT. THE FLEX COUPLING SHOWED NO ABNORMAL WEAR OR DAMAGE. NOTE: THE DRIVESHAFT HAD ONE OVERTORQUE (110 PERCENT) INCIDENT. SHAFT WAS REMOVED FOR OVERHAUL AT THAT TIME. TSO, 1,441.8 HOURS.