What was found
DURING CRUISE, A MODERATE VIBRATION WAS FELT IN THE CONTROLS. ACFT WAS AT FL220, APPROX 295 KNOTS INDICATED. VIBRATION BECAME MORE PRONOUNCED. CREW DIVERTED. VIBRATION WAS CONSTANT FROM FL220 DOWN TO ABOUT 8500 FT. LANDING WAS UNEVENTFUL. MX FOUND THE LOWER RUDDER TRIM TAB HINGE PIN DROPPED INSIDE THE RUDDER DUE TO COTTER KEY FAILURE. MX REMOVED THE RUDDER AND REPLACED BOTH TRIM TAB HINGE HALVES AND HARDWARE. RUDDER WAS BALANCED REINSTALLED AND A SUCCESSFUL OPS CHECK FLIGHT WAS PERFORMED. THE AFT WAS RETURNED TO SERVICE.