What was found
DURING FLT NR EE1100 AT LEVEL 31,000 AIRCRAFT EXPERIENCED RUDDER VIBRATION, AIRCRAFT DESCENDED TO FLIGHT LEVEL 11,000 DUMPED FUEL AND REDUCED AIRSPEED TO 210 KNOTS AT WHICH TIME VIBRATION CEASED. AIRCRAFT WAS DIVERTED TO JFK FOR INSPECTION/TROUBLESHOOTING. AT JFK REPLACED RUDDER PRESSURE REGULATOR AND RELIEF VALVE. (M)