As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT BEGAN TO EXPEREINCE A 1 TO 1 VERTICAL VIBRATION AND I FELT FEEDBACK IN THE CYCLIC. DECLARED AN EMERGENCY, AND EXECUTED A ROLL ON LANDING WITHOUT INCIDENT. MX INSPECTED THE ACFT AND DISCOVERED THAT THE LOWER BEARING ON THE BLACK PITCH CHANGE LINK HAD FAILED AND CAME UNSTAKED FROM THE ROD END.