MLG ON APCH VECTORS HAS TCASII RA; THEN DSNDS BELOW ASSIGNED ALT.

Narrative

DURING APCH TO FLL ARPT ON DOWNWIND LEG ON VECTORS FOR APCH TO 9L; I REQUESTED TURN TO FINAL THINKING THAT THE CTLR WOULD ISSUE A VISUAL APCH. A CLRNC WAS ISSUED TO TURN TO A 130 DEG HDG TO INTERCEPT THE FINAL APCH COURSE; AND MAINTAIN 2500 FT UNTIL INTERCEPTING THE LOC. DURING THE TURN TO FINAL THE TCASII ALERTED US TO A POP-UP INTRUDER. THE TARGET APPEARED TO BE ALMOST UNDER US; OR OVER US; AS IT WAS YELLOW; AND SLIGHTLY TO THE LEFT OF OUR POS. IT WAS IMPOSSIBLE TO TELL WHETHER THE ACFT WAS ABOVE OR BELOW AS IT'S TARGET WAS SUPERIMPOSED OVER THE ACFT SYMBOL. I STOPPED THE TURN ON A 180 DEG HDG AND LEVELED OFF AT 3000 FT TO AVOID THE TARGET WHILE ATTEMPTING TO LOCATE THE TARGET VISUALLY. THE OTHER ACFT WAS NEVER SEEN BY EITHER PLT; NOR HAD THE APCH CTLR ISSUED TA. AFTER THE CONFLICT WAS OVER; I CONTINUED THE TURN TO INTERCEPT THE FINAL APCH COURSE. THE RWY WAS IN SIGHT VISUALLY; AND I BEGAN A DSCNT FOR LNDG. THE DELAY IN THE TURN HAD TAKEN US THROUGH THE LOC; BUT VISUALLY WE WERE VERY CLOSE TO THE FINAL APCH COURSE. IT SEEMED THE NORMAL THING TO CONTINUE THE DSCNT FOR LNDG; BUT I HAD DEVIATED FROM THE PUBLISHED APCH PROC. THE CTLR THEN ASKED WHY WE WERE AT 1500 FT WHEN WE HAD BEEN ASSIGNED 2500 FT FT UNTIL INTERCEPTING THE LOC. IN THE DISTR OF THE PREVIOUSLY MENTIONED TCASII ALERT; I HAD JUST ASSUMED THAT WE HAD BEEN CLRED FOR A VISUAL APCH; WHEN IN FACT; THAT CLRNC HAD BEEN 'CLRED FOR THE APCH;' NOT THE VISUAL APCH. I REALIZE THAT THERE IS NO ROOM FOR ASSUMPTIONS WHEN COMPLYING WITH ATC CLRNCS; BUT BECAUSE MY ATTN HAD BEEN FOCUSED ON THE TCASII INTRUDER; I HAD ALLOWED MY MIND TO THINK THAT WHAT I HAD EXPECTED TO HAPPEN HAD ACTUALLY HAPPENED. IN DISCUSSING THIS WITH MY FO; MUCH TO MY CHAGRIN; I REALIZED THAT I HAD MISUNDERSTOOD THE CLRNC.