WHILE ON VFR APCH TO SNY SHORT FINAL (UNCTLED FIELD); A PA28 PLT IS FORCED TO GO AROUND WHEN AN SW4 ENTERED THE RWY AND BEGAN TO BACK TAXI; CAUSING A RWY INCURSION.

Narrative

APPROX 17 MI OUT FROM OUR DEST OF SNY; NE; ZDV CLRED ME TO DSND AT PLT'S DISCRETION FROM 9000 FT TO 6000 FT. WE EXPECTED A VISUAL APCH. ABOUT 13 MI OUT OF OUR DEST; I BEGAN THE DSCNT TO 6000 FT AND AT 12 MI I NOTIFIED CTR I HAD THE ARPT IN SIGHT AND WAS CANCELING IFR. CTR ACKNOWLEDGED. AT 10 MI OUT AND DSNDING; I BROADCAST ON SNY CTAF MY POS AND INTENTIONS TO LAND AT SNY. AT 5 MI OUT; I AGAIN BROADCAST MY POS AND INTENTION TO LAND ON RWY 12. AT 3 MI OUT; I MADE YET ANOTHER BROADCAST OF MY POS AND INTENTIONS TO LAND ON RWY 12 AND BEGAN THE APCH TO LNDG CHKLIST (THIS INCLUDED TURNING ON THE LNDG LIGHTS AT THIS TIME; TAIL AND WINGTIP STROBES WERE ALREADY ON). AT 1 MI OUT; FINAL CHKLIST WAS COMPLETED. DURING FINAL DSCNT AND LESS THAN 1/2 MI FROM THE APCH END OF RWY 12; A SWEARINGEN MERLIN IV METROLINER PULLED ONTO RWY 12 AND BEGAN TO BACK-TAXI. IT WASN'T UNTIL AFTER THE MERLIN PLT HAD COMPLETED THE TURN ONTO THE ACTIVE RWY 12 AND BEGAN THE BACK-TAXI THAT HE ANNOUNCED HIS INTENTIONS AND ASKED IF THERE WAS ANY OTHER TFC IN THE AREA; TO PLEASE ADVISE. WHILE THE MERLIN PLT WAS STILL BROADCASTING I HAD ALREADY ABORTED THE LNDG AND INITIATED GAR PROCS. I ADVISED THE MERLIN PLT OF THE FACT I WAS ON A SHORT FINAL FOR RWY 12 AND HAD TO ABORT BECAUSE OF HIM. HE INITIALLY ACCUSED ME OF FAILURE TO ANNOUNCE MY POS AND INTENTIONS BUT AFTER ASSURING HIM I HAD MADE AT LEAST 3 SUCH ANNOUNCEMENTS; HE NO LONGER TOOK ISSUE WITH ME. IT WAS VERY OBVIOUS TO ME THAT THE MERLIN PLT HAD MADE 3 VERY SERIOUS ERRORS: HE DID NOT TAKE THE TIME TO LOOK AND SEE IF ANYONE MIGHT HAVE BEEN LNDG; NOR DID HE ANNOUNCE HIS INTENTIONS PRIOR TO PULING OUT ONTO AN ACTIVE RWY. HE ALSO FAILED TO MONITOR HIS RADIO AS TO WHERE OTHER TFC MIGHT BE IN THE AREA.