STRAIGHT IN ACR FLT ABRUPTLY MAKES A L TURN ON FINAL AND CONFLICTS WITH AN ACR AT SAME ALT ON BASE LEG.

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THE INCIDENT OCCURRED AFTER ACR X WAS ASSIGNED A HDG OF 210 DEGS TO INTERCEPT THE LOC BACK COURSE RWY 23 AT CLT. WHEN ACR X WAS APPROX 14 MI FROM ATELL; HE WAS CLRED TO MAINTAIN 4000 FT UNTIL ATELL CLRED FOR LOC BACK COURSE RWY 23 APCH. ACR Y WAS ON A L DOWNWIND FOR RWY 23 DSNDING TO 4000 FT. ACR Y WAS TURNED L TO 320 DEGS FOR A BASE TO FINAL; REF ACR X. AT APPROX THE SAME TIME; ACR X WAS INTERCEPTING THE LOC BACK COURSE. ACR X MADE A HARD L TURN TO 160 DEGS DIRECTLY AT ACR Y. BOTH ACFT WERE LEVEL AT 4000 FT. WHEN I OBSERVED THE TURN OF ACR X; I QUESTIONED HIS HDG AND WAS TOLD '...I'M TURNING TO 230 DEGS; REQUEST VECTORS TO CLT.' I IMMEDIATELY ISSUED A TFC ALERT TO ACR X AND A CLRNC TO CLB TO 5000 FT. I IMMEDIATELY ISSUED TFC ALERT TO ACR Y AND A CLRNC TO DSND TO 3000 FT. STANDARD SEPARATION WAS RE-ESTABLISHED AND ACR X AND ACR Y LANDED SAFELY. ACR Y ADVISED THAT; '...THAT WAS DAMNED CLOSE.' THE PLT OF ACR X PHONED THE TRACON AND TOLD THE SUPVR THAT HE HAD TROUBLE DISARMING HIS AUTOPLT. I WONDER IF THE AUTOPLT WAS SET FOR A BACK COURSE APCH.