ACFT HAS NMAC AT AN UNCTLED AIRFIELD.

Narrative

I WAS RETURNING TO MY HOME FIELD (ROMEO - D98) TO LAND AND ENTERED A XWIND FOR THE ACTIVE RWY; RWY 18. I WAS APPROX OVER THE ACTIVE RWY WHEN I HEARD ANOTHER ACFT ANNOUNCE HE WAS ENTERING A DOWNWIND FOR RWY 18. I LOOKED AROUND AND SAW A SMALL HELI SLIGHTLY ABOVE ME AND ABOUT 500 YARDS IN FRONT. I WONDERED IF THIS WAS THE OTHER ACFT ENTERING A DOWNWIND SINCE I DIDN'T RECALL THE ACFT TYPE THAT I JUST HEARD. BASED ON THE POS; APPARENT SPDS IMMEDIATELY TURN INTO MY DOWNWIND LEG SOONER THAN I NORMALLY WOULD HAVE. AS SOON AS I TURNED; I LOST SIGHT OF THE HELI. I THEN PROCEEDED TO LAND UNEVENTFULLY; WHILE ANNOUNCING ON UNICOM MY DOWNWIND; BASE AND FINAL LEGS. AFTER I LANDED I HEARD THE HELI ANNOUNCE THAT IT WAS ON A R BASE FOR RWY 9; AND I ALSO HEARD ANOTHER PLANE (A LOW WING VARGA) ON FINAL FOR RWY 18. AT THAT POINT I REALIZED THE VARGA WAS THE ACFT I HEARD ORIGINALLY ANNOUNCING ITS DOWNWIND INTENTIONS. THE VARGA LANDED AND THEN THE HELI USED RWY 9 TO APCH THE HANGAR AREA. ALTHOUGH I THOUGHT THIS WAS SOMEWHAT UNUSUAL; I DIDN'T THINK ANY MORE ABOUT IT UNTIL ONE OF THE ARPT PERSONNEL CALLED ME AT WORK ON MONDAY AND INTIMATED THAT THE HELI PLT COMPLAINED THAT I ACTED IN AN UNSAFE MANNER. I TAKE EXCEPTION TO THAT AND AM THEREFORE FILING THIS RPT. ALSO DURING THE DISCUSSION WITH THE ARPT PERSON; I WAS TOLD THAT IT IS NORMAL FOR HELIS TO FLY R HAND PATTERNS (WHICH DOES MAKE SOME SENSE TO ME) AND; SINCE ROMEO IS UNCTLED; CAN SELECT ANY RWY (WHICH I DON'T DISAGREE WITH). HOWEVER; I BELIEVE ONCE A PLT SELECTS A RWY OTHER THAN THE ACTIVE; IT IS INCUMBENT UPON HIM TO SEE AND AVOID ALL OTHER TFC. I DID TALK TO 3 OTHER PLTS ABOUT THIS INCIDENT (2 OF THEM CFII'S) AND NONE OF THEM WERE AWARE OF THE RULES COVERING THIS SIT. THEREFORE; IT SEEMS THAT SOME SORT OF 'REFRESHER' INFO SHOULD BE MADE AVAILABLE COVERING THIS SIT NOW THAT PERSONAL HELIS AT UNCTLED AIRFIELDS ARE BECOMING MORE COMMON. (THIS WAS MY FIRST ENCOUNTER WITH A HELI IN THE PATTERN AT AN UNCTLED AIRFIELD SINCE I STARTED FLYING IN 1974).