What was found
UPON LIFTOFF FROM MGM, THE CAPTAIN OBSERVED A STRONG VIBRATION FOR ABOUT 15-20 SECONDS. THE CAPTAIN DECLARED AN EMERGENCY AND RETURNED TO MGM FOR AN UNEVENTFUL LANDING. MAINTENANCE INSPECTED THE DOORS, PANELS, DE-ICE BOOTS, AND LANDING GEAR AND FOUND NO DEFECTS. THE LEFT INBOARD TIRE WAS DISCOVERED TO HAVE A TEN INCH FLAT SPOT. MAINTENANCE REMOVED AND REPLACED THE FLAT SPOTTED LEFT TIRE. (M)