What was found
ON APPROACH, CREW REALIZED TAIL ROTOR EFFECTIVENESS HAD BEEN LOST. CREW ABORTED APPROACH AND PERFORMED SUCCESSFUL RUN-ON LANDING AT NEARBY AIRPORT. UPON SHUTDOWN AND INSPECTION BY MX, IT WAS FOUND THAT THE TAILROTOR PITCH BEAM RETAINING NUT AND LOCK RING WERE MISSING. CAUSE UNDETERMINED AT THIS TIME. IT IS NOT YET KNOWN WHETHER THIS WAS A MECHANICAL FAILURE OR IMPROPER INSTALLATION PROCEDURES. INVESTIGATION ONGOING.