What was found
(CAN) ON A FLIGHT ON DECEMBER 21, 2012, THE FLIGHT CREW NOTED A LATERAL VIBRATION THAT BECAME MORE PRONOUNCED DURING DECENT. THE FLIGHT CREW TERMINATED THE FLIGHT AND RETURNED TO BASE. A SUBSEQUENT VISUAL INSPECTION OF THE MAIN ROTOR HEAD FREQUENCY ADAPTERS REVEALED A 30 MM LONG SEPARATION OF THE BONDED ELASTOMERIC MATERIAL FROM THE METAL CENTRAL CORE. THE FREQUENCY ADAPTERS HAD BEEN VISUALLY INSPECTED JUST PRIOR TO THE FLIGHT AS PART OF A DAILY/15 HOUR INSPECTION, AND NO DEFECTS HAD BEEN NOTED. THE MATCHED SET OF 3 FREQUENCY ADAPTERS WAS REMOVED FROM SERVICE, AND REPLACED WITH A NEW SET OF 3 THAT WE HAD ON HAND. THE VIBRATION WAS ELIMINATED AND THE TRACK AND BALANCE WAS VERIFIED WITH OUR VIBREX 2000.