What was found
VIBRATION IN TAIL ROTOR WAS FELT DURING MAINTENANCE CHECK FLIGHT AFTER DE-ICING. WHEN HEAT WAS APPLIED TO TAIL ROTOR BLADE, WATER WAS SEEN COMING FROM STRAP AREA AS TRAPPED ICE MELTED. OUTSIDE AIR TEMPERATURE WAS BELOW FREEZING. SB64F15-3 WAS PERFORMED BEFORE HEAT WAS APPLIED WITH NEGATIVE RESULT. SB WAS PERFORMED AGAIN AFTER HEATING WITH POSITIVE RESULT FOR WATER ENTRAPMENT. TRB WAS REMOVED FROM AIRCRAFT AND SENT TO THIS REPAIR STATION FOR INVESTIGATION.