SMA DESCENDED BELOW MINIMUMS AND MADE AN UNAUTHORIZED CIRCLING APCH.

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I WAS CLRED FOR THE LOC 22 APCH TO NEWPORT BY QUONSET APCH. QUONSET ADVISED THE PASSAGE OF SMARI; THE 6 MI FAF AND RELEASED ME TO ADVISORY FREQ. I RPTED INBND ON THE LOC APCH; 5 MI FINAL. THE UNICOM FREQ 122.8 WAS OCCUPIED FOR A PERIOD OF TIME BY TFC AT OTHER FIELDS; AND I OCCUPIED FOR A PERIOD OF TIME BY TFC AT OTHER FIELDS; AND I HEARD 'NEWPORT TFC; SAY POS.' I RPTED A 2 MI FINAL FOR 22; AND THE PLT THEN CONCENTRATED ON THE APCH WHICH WOULD OBVIOUSLY BE TO MINIMUMS DUE TO A LOW CEILING OF FOG. THE ARPT AREA BECAME VISIBLE BEFORE MAP BY TIME; SO I DSNDED BELOW THE 680' MDA FOR STRAIGHT IN. THE CEILING WAS VARIABLE; HOWEVER AND I FLEW THROUGH LOWER FOG. THE PLT BECAME BRIEFLY DISORIENTED AND DRIFTED RIGHT OF COURSE; RESULTING IN A 4-DOT NEEDLE DEFLECTION. I CORRECTED AND CONTINUED; BREAKING OUT AGAIN OVER THE THRESHOLD AT APPROX 500'. THE PLT DID NOT BELIEVE STRAIGHT IN WOULD BE POSSIBLE; AND TURNED RIGHT 30 DEGS TO CIRCLE LEFT AND LAND RWY 4. HOWEVER; SURFACE WINDS DID NOT ENCOURAGE A DOWNWIND LNDG AND I BROKE OFF THE APCH TO RWY 4 AT 50'; CLBING TO THE RIGHT. A VERY STEEP DSNDING LEFT TURN FOLLOWED; ALLOWING A XWIND LNDG ON RWY 16. UPON BEGINNING THE LEFT TURN I NOTICED A HELI LIFTING OFF AT THE INTXN OF THE 2 RWYS. I CONTINUED JUST PAST THE HELI AND LANDED; STOPPING JUST SHORT OF THE END OF THE RWY. THE PLT OF THE HELI WAS CONCERNED THAT I WAS NOT AWARE OF THE HELI'S PRESENCE. HAVING FLOWN A VERY TIGHT AND SOMEWHAT UNUSUAL CIRCLE-TO-LAND PATTERN DUE TO VIS RESTRICTIONS; I AM CONCERNED ABOUT THE SAFETY OF A HELI PRACTICING AIR TAXIING VERY CLOSE TO THE RWYS OF AN UNCTLED ARPT WITH ACFT SHOOTING APCHS TO LAND AND WX OBVIOUSLY AT MINIMUMS. A CIRCLE-TO-LAND APCH IS VERY DIFFICULT; ESPECIALLY IN LOW VIS. I BELIEVE ALL RWYS SHOULD BE AVAILABLE TO AN ACFT ON AN APCH TO AN UNCONTROLLED FIELD WHEN THE FIELD IS IFR. ANY UNUSUAL MOVEMENT PERCEIVED AS UNPREDICTABLE BY A PLT ATTEMPTING TO LAND IS VERY DISTRACTING AND POTENTIALLY DANGEROUS.