AIRBUS A320 FLC TOOK EVASIVE ACTION DURING DOWNWIND LEG IN RESPONSE TO A TCASII RA AND THE VISUAL SIGHTING OF THE OTHER. APCH CTLR APOLOGIZED FOR NOT HEARING THE CAPT'S READBACK OF A CLRNC INTENDED FOR THE OTHER ACFT.

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WE HAD BEEN ON A SERIES OF DELAYING VECTORS DUE TO TFC ON FINAL AT DEST ARPT. OUR LAST ASSIGNED HEADING WAS 360 DEGS AT 6000 FT MSL. THIS WAS ANOTHER DELAY VECTOR AS WE WERE ALREADY DUE N OF THE ARPT AND HAD BEEN ON A 090 DEG HDG FOR DOWNWIND TO RWY 27R. WE RECEIVED A TCASII TA; FOLLOWED IMMEDIATELY BY AN RA. I HAD THE TFC IN SIGHT AT OUR 11 O'CLOCK POS AND INITIATED AN AUTOPLT OFF DSNDING R TURN. THE OTHER AIRPLANE APPEARED TO BE ON AN EASTERLY HEADING. PRESUMABLY ALSO ON DOWNWIND TO THE SAME RWY. THAT AIRPLANE CONCURRENTLY BEGAN A CLBING R TURN I FELT AS THOUGH WE WERE IN THE RIGHT; BECAUSE I DISTINCTLY HEARD OUR CALL SIGN GIVEN THE 360 DEG HDG; AND FREQ CONGESTION AS THE CTLR WAS WORKING MANY AIRPLANES. I FEEL THE OVERWORKED CTLR JUST LOOKED AT 1 AIRPLANE AND READ OFF OUR CALL SIGN. THE CAPT FELT WE WERE IN THE WRONG. HE FELT; AS PNF; HE HAD READ BACK A CLRNC FOR ANOTHER AIRPLANE. IF THIS IS THE TRUE CASE; THEN THE CTLR DID NOT CATCH OUR MISTAKEN READBACK. AND NEITHER DID THE CREW OF THE AIRPLANE FOR WHOM THE TURNING VECTOR WAS FOR. I FEEL THAT RELIEVING CTLRS OF THE BURDEN TO LISTEN TO READBACKS OF CLRNCS FOR ACCURACY IS POOR TECHNIQUE. I AM ALL FOR MAKING THE STRESSFUL JOB OF ATC EASIER; BUT THE ANSWER IS NEWER EQUIP OR MORE CTLRS COVERING SMALLER PARCELS OF AIRSPACE. IF CTLRS ARE NOT GOING TO LISTEN TO READBACKS; THEN WHY ARE WE; AS PLTS; EVEN BOTHERING TO RESPOND? I THOUGHT THE WHOLE PURPOSE OF READING BACK AN ATC CLRNC WAS TO ESTABLISH 2-WAY COM FOR THE PURPOSE OF ACCURACY. SUPPLEMENTAL INFO FROM ACN 520955: UPON HDOF TO PHL TWR; PHL APCH APOLOGIZED STATING THAT HEADING WAS FOR ANOTHER ACFT AND THAT HE FAILED TO CORRECT OUR ACKNOWLEDGMENT.