BK117 HELI MAKES PRECAUTIONARY LNDG IN RESPONSE TO STRONG VIBRATION. PLT ACCOMPLISHES TEMPORARY REPAIR OF LOOSE TAPE ON MAIN ROTOR; AND RETURNS TO BASE FOR INSPECTION AND REPAIR.

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I WAS FLYING ON A N EASTERLY HDG AT APPROX 800 FT MSL. INDICATED AIRSPD WAS 122 KTS. I HEARD A LOUD SLAP LIKE A LARGE BUG HAD IMPACTED SOME PORTION OF THE AIRFRAME OR WINDSCREEN. NOTHING COULD BE OBSERVED FROM THE COCKPIT; AND FLT WAS CONTINUED. IN LESS THAN 2 MINS; THE HELI STARTED TO EXHIBIT A PRONOUNCED VERT VIBRATION. WITHIN A FEW SECONDS; THE VIBRATION BECAME MODERATE AND AIRSPD WAS REDUCED. THE VIBRATION ALSO DIMINISHED. I WAS ON RADAR WITH MYRTLE BEACH APCH CTL; AND DECLARED WITH THEM THAT I WAS MAKING A PRECAUTIONARY LNDG; BECAUSE OF MODERATE VERT VIBRATIONS. THE APCH AND LNDG WERE UNEVENTFUL. AFTER NORMAL SHUTDOWN; THE POSTFLT REVEALED A SMALL TEAR ON THE LEADING EDGE OF THE YELLOW BLADE TAPE. A FLAP OF TAPE WAS PROTRUDING JUST ENOUGH TO INTERFERE WITH THE AIRFOIL ON THIS BLADE. I THEN TRIMMED THIS SMALL PIECE OF TAPE OFF BY JUST TEARING WHERE IT HAD ALREADY STARTED TO TEAR. I REMOVED THE TORN TAPE MEASURING ABOUT 1 INCH BY 1/2 INCH FROM THE BLADE. I FELT I HAD A SMOOTH ENOUGH BLADE SURFACE TO RETURN TO BASE AND HAVE REPAIRS MADE; AND LET THE A&P MECH LOOK AT IT. I THEN RAN THE ACFT UP TO FULL RPM; SET FOR ABOUT 1 MIN; THEN HOVERED FOR 30-40 SECONDS; AND TOOK OFF ACCELERATING SLOWLY. ALL SEEMED NORMAL; AND THE ACFT FLEW AS SMOOTH AS BEFORE. I DECLARED THAT MY MAINT FLT CHK WAS GOOD AND THAT THE ACFT WAS AIRWORTHY AND SVCABLE. THE ACFT WAS FLOWN BACK TO BASE FOR FURTHER INSPECTION UNEVENTFULLY.