C208 INBOUND TO SJU TURNS BASE AND CONFLICTS WITH A GLF4 ON A STRAIGHT-IN RESULTING IN AN OPERROR.

Narrative

I WAS WORKING LCL CTL DURING A DEP PUSH AT XA00. A CESSNA CARAVAN WAS INBOUND TO THE ARPT FROM THE E AND A GULFSTREAM JET WAS INBOUND FROM THE W. THE CARAVAN CALLED INITIALLY TO RPT INBOUND ABOUT 7 MI SE OF THE FIELD. AT THIS TIME I WAS MAKING A MANUAL HDOF ON AN ACFT THAT AUTO-ACQUIRED WITH THE WRONG CALL SIGN ON THE RADAR. THE CARAVAN INBOUND FROM THE SE CALLED AGAIN AND I TOLD THE ACFT 'CONTINUE; I WILL HAVE A LNDG CLRNC FOR YOU MOMENTARILY.' THINKING THAT THE ACFT WOULD CONTINUE ON A REGULAR TFC PATTERN; THE PLT EXTENDED DOWNWIND LEG AT HIS LEISURE. AT THE SAME TIME; A GULFSTREAM JET WAS COMING ON THE 7 MI FINAL MARKER. WHEN I SAW THE CARAVAN EXTENDING DOWNWIND; I TOLD THE PLT TO TURN BASE IMMEDIATELY; NOT TAKING INTO CONSIDERATION THE SPD DIFFERENTIAL BTWN THE CARAVAN AND THE GULFSTREAM. I POINTED OUT THE GULFSTREAM TO THE CARAVAN TO WHICH THE PLT REPLIED WITH THE PHRASE 'I HAVE THE TFC IN SIGHT.' THE CTLR WORKING THE W AND FINAL CTL INTO THE SAN JUAN COMPLEX ASKED ME WHAT I WAS DOING WITH THE CARAVAN; TO WHICH I TOLD HIM THAT I WAS TURNING HIM TOWARDS THE ARPT AND THAT THE CARAVAN'S PLT HAD THE TFC IN SIGHT. IMMEDIATELY; I SWITCHED THE CARAVAN TO THE RWY N OF THE TWR SO THE GULFSTREAM COULD CONTINUE STRAIGHT IN TO THE RWY S OF THE TWR; BUT AS I WAS DOING THAT I SAW THE GULFSTREAM BREAKING OUT OF TFC TO THE N. DURING THE ENTIRE SIT; I WAS TALKING ONLY TO THE CARAVAN'S PLT WHILE THE GULFSTREAM'S PLTS WERE IN CONTACT WITH THE RADAR CTLR AT ALL TIMES.