ACR X POSSIBLE LTSS WITH ACR Y AFTER DSCNT TO OCCUPIED ALT. POSSIBLE SYS ERROR.

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ACR X MFE TO DFW NORMAL APCHS TO DFW; VFR; RADAR VECTORS ON DOWNWIND FOR RWY 18R. HDG 350 DEG AT 6000 ATC GIVES DSCNT TO 3000 FT. R TURN TO 160 DEG HDG TO PICK UP THE ILS RWY 18R. AFTER PASSING THROUGH ABOUT A 090 DEG HDG CTL ADVISES THAT THIS IS NOT GOING TO WORK AND GIVES A TURN BACK L TO 310 DEG LEVEL AT 5000 FT. THEN GIVES A DSCNT TO 4000 FT. THIS PUT US HDG DIRECTLY INTO ONCOMING TFC AT 4000 FT ON THE ILS. I SHALLOWED THE DSCNT. NO EVASIVE ACTION TAKEN. NO TCASII INSTALLED ON THE AIRPLANE. SUPPLEMENTAL INFO FROM ACN 190983. VECTORS FOR APCH TO ILS FOR RWY 18R AT DFW; APCH CTLR ASSIGNED A HDG OF 160 DEG TO INTERCEPT AND TO CROSS JOHAN AT 3000 FT OR ABOVE. ON HDG AND DSNDING THROUGH APPROX 5200 FT; CTLR ISSUED A CLRNC TO MAINTAIN 5000 FT; TURN L TO HDG 310 DEG. DURING TURN WE WERE CLRED TO 4000 FT AND NOTICED INBOUND ACR Y AS WE CAME THROUGH 360 DEG HDG. BELIEVE ACR Y WAS AT 4000 FT. WE STOPPED DSCNT THEN RECEIVED TURN TO 260 DEG HDG. ACR Y MADE SLIGHT R TURN TO AVOID US. ONCE CLR WE DSNDED AND CONTINUED WITH VECTORS BACK TO FINAL AND SUBSEQUENT LNDG. CTLR APOLOGIZED AND STATED HE HAD US CONFUSED WITH ANOTHER ACFT.