What was found
EN ROUTE AIRFRAME VIBRATION WAS FELT IN ALL PHASES OF FLIGHT, MOST NOTICEABLE IN CLIMB & CRUISE AT SPEED OF 310 KTS. MX VISUALLY INSPECTED WING TO BODY FAIRING SEALS, MLG DOORS, AIR COND & PAX ENTRY DOORS, NO DEFECTS NOTED. PERFORMED ELEVATOR FREE PLAY CHECK, NO DEFECTS NOTED. PERFORMED RUDDER FREE PLAY CHECK & FOUND YELLOW & BLUE RUDDER SERVO CONTROLS OUT OF LIMITS. R & R YELLOW & BLUE RUDDER SERVO CONTROLS. OPS CHECK GOOD. TEST OF RUDDER SERVO CONTROL CONFIRMED FAILURE OF UNIT FOR FAILING DAMPING TEST. UNIT WAS FOUND LEAKING AT ROD END, SWIVEL BEARING, & BALL BEARING ON LEVER ARM ASSEMBLY, SWIVEL BEARING AT END EYE & CYLINDER HOUSING WERE ALL WORN, & BOTH CONTROL & BYPASS VALVES WORN BEYOND LIMITS.