What was found
AIRCRAFT WAS GROUNDED: AN EMERGENCY WAS DECLARED AND THE AIRCRAFT RETURNED TO LAX DUE TO THE FLIGHT CREW REPORTING THAT INFLIGHT VIBRATIONS FELT FROM ABOUT 13,000 THROUGH CLIMB OUT 30,000 FEET APPROX SPEED 340. VIBRATION WAS FELT ON LEFT SIDE ON BOTH RUDDER PEDALS VIBRATIONS, FLUTTERING, A KICKING BACK FEELING WHEN FLT CREWS FEET RESTED ON BOTH PEDALS. PLUS, 3 FLT ATTENDANTS REPORTED VIBRATIONS COMING FROM GALLEY FLOOR NEAR R4 & R3 DOORS, VIBRATIONS THEY FELT THRU THEIR FEET. FLT CREW REPORTED THAT ONCE SLOWING DOWN AT, BELOW 280 K VIBRATIONS GO AWAY MOSTLY. ACFT LANDED SAFELY AT LAX WITHOUT FURTHER INCIDENT. (OPEN)