C172 PVT PLT EXPERIENCED A NON TWRED RWY INCURSION AT PYM.

Narrative

AT PYM; A NON TWRED ARPT AND HAVING COMPLETED MY PREFLT CHKLIST AND RUN-UP OF THE C172/U; I ANNOUNCED ON THE COM RADIO FREQ 123.0 THAT I WAS TAXIING INTO POS FOR RWY 24 STRAIGHT OUT DEP. SUDDENLY A VOICE BOOMED OUT OF MY HEAD SET FROM THE PLT OF A 2 ENG JET BEECHCRAFT THAT HE WAS ON SHORT FINAL AND I WAS IN VIOLATION OF ARPT PROCS. I HAD CROSSED THE YELLOW HOLD SHORT LINE AND WAS NOT ON THE ACTUAL RWY; I LOOKED UP AND SAW THE BEECHCRAFT APPROX 300 FT ABOVE TOUCHDOWN ON SHORT FINAL. THE PLT MADE SOME ANGRY COMMENTS THAT I WAS IN VIOLATION FOR NOT HOLDING SHORT. HOWEVER; HE DID HEAR MY COM THAT I WAS TAKING THE ACTIVE RWY; BUT I NEVER HEARD HIM ANNOUNCE THAT HE WAS ON SHORT FINAL. BE THAT AS IT MAY; I WAITED BEFORE TAKING THE ACTIVE RWY; FOR THE BEECHCRAFT PLT TO ANNOUNCE THAT HE WAS CLR OF THE ACTIVE RWY. WHEN I INQUIRED OF HIM IF HE WAS CLR OF THE ACTIVE; HE ANGRILY RESPONDED THAT HE ANNOUNCED CLRING; BUT I HEARD NO SUCH COM. I THEN ANNOUNCED ON THE COM THAT I WAS TAKING THE ACTIVE RWY 24 FOR STRAIGHT-OUT DEP AND THEN NW TO ZZZ. THE FLT WAS UNEVENTFUL AND I FORGOT ABOUT THE INCIDENT AT PLYMOUTH. THIS INCIDENT HAS TAUGHT ME THAT AT NON TWRED ARPTS NOT TO RELY ONLY ON RADIO COM BUT ALSO BEFORE XING THE HOLD SHORT LINE TURN THE ACFT; ESPECIALLY HIGH WING; INTO THE DSNDING APCH PATTERN FOR BETTER VIEWING OF LNDG ACFT.