As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE IN-FLIGHT, 2-13-97 APPROX 4 PM, ATTACHMENT BOLT VIBRATED OUT OF THE UPPER END OF THE COLLECTIVE CONTROL ROD. A LEATHER PUNCH WAS INSERTED IN THE CLEVIS AND THROUGH THE BALL END AND HELD IN PLACE RESTORING COLLECTIVE CONTROL. AIRCRAFT LANDED WITHOUT INCIDENT. SUSPECT NUT CAME OFF THE BOLT. SUGGEST NUT BE REPLACED WITH A CASTELLATED NUT AND KEYED.