IMPROPER CANCELLATION OF IFR CLRNC BY AN ACFT ON GND LED TO A TCASII RA ON RPTR ACFT DURING IFR APCH. ARPT UNCTLED AND ACFT LNDG BROADCAST ON CTAF THEIR LOCATION AND INTENTIONS. APPARENT MISUNDERSTANDING ABOUT CALL SIGNS WHEN THE LEAD ACFT ON APCH ASKED TO HAVE IFR CANCELLATION RELAYED TO CTR AND ACFT ON GND MISTOOK THE #2 ACFT AS CANCELING.

Narrative

WHILE FLYING INTO STC WE WERE TOLD BY CTR THAT WE WERE #3 FOR AN APCH. WE WERE THEN VECTORED FOR SEPARATION. THE #1 ACFT CANCELED HIS IFR CLRNC THROUGH THE #2 ACFT. THE #2 ACFT WAS THEN CLRED FOR THE VOR DME RWY 13 APCH AT STC. WE WERE THEN CLRED DIRECT TO THE VOR TO HOLD AT 5000 FT. JUST PRIOR TO REACHING THE VOR; WE WERE CLRED FOR THE VOR DME RWY 13 APCH. WE WERE TOLD TO CHANGE TO ADVISORY FREQ WHICH WE PROMPTLY HAD DONE AND MADE A POS RPT ON CTAF. ASSUMING THE #2 ACFT HAD CANCELED THROUGH PRINCETON FSS; WE HAD NO REASON TO QUESTION THE CLRNC FOR THE APCH. AFTER XING THE VOR; WE BEGAN OUR DSCNT TO THE APCH TRANSITION ALT OF 2700 FT. AS WE APCHED 3500 FT; AN ACFT APPEARED ON OUR TCASII 800 FT BELOW US (2700 FT MSL) AND APPROX 2 MI AWAY AT OUR 12 O'CLOCK POS. WE RECEIVED AN RA FROM THE TCASII AND BEGAN TO CLB. WE THEN SWITCHED FREQS BACK TO CTR. WHEN WE ASKED CTR IF THERE WAS ANOTHER ACFT ON THE APCH; THE #2 ACFT RESPONDED THAT HE WAS INBOUND ON THE APCH AND HAD NOT CANCELED HIS IFR CLRNC. WE CAME TO LEARN THAT THE #2 ACFT'S CLRNC WAS CANCELED BY ANOTHER ACFT ON THE GND AWAITING A CLRNC FROM PRINCETON FSS. IF WE HAD NOT HAD TCASII; THE SIT WOULD HAVE RESULTED IN TWO ACFT CONVERGING AT THE SAME ALT ON THE SAME RADIAL. THE SIT WAS CAUSED BY THE ACFT ON THE GND WHICH FALSELY IDENTED THE ACFT TYPE AND 'N' NUMBER AND VOLUNTARILY CANCELED ANOTHER ACFT'S IFR CLRNC. ANOTHER ACFT SHOULD NOT BE ABLE TO CANCEL ONE'S CLRNC UNLESS VERBALLY COMMUNICATED TO THAT ACFT THAT THEY WOULD LIKE THEIR CLRNC CANCELED. ALSO; IT IS VERY OBVIOUS TO ALL PLTS AT MY AIRLINE THAT STC NEEDS AT LEAST A PART TIME ATCT.