What was found
AT 12000 THE AIRCRAFT STARTED TO PRODUCE HEAVY UNUSUAL VIBRATION IN THE HULL THE AND A VERY LOUD VIBRATING NOISE. WE DECLARED EMERGENCY AND RETURNED TO FIELD. NO MASTER WARNING AND NO MASTER CAUTIONS MESSAGES AND ALL ENG VIBRATIONS WERE WITHIN NORMAL RANGE. (FLT#5087) FO: 10/23/2018 CLOSED REMOVED MLG BAY FORWARD FAIRING AND REPLACED WORN BRACKETS AND REINSTALLED FAIRING IAW AMM. OPS CHECK GOOD.