ACR INBOUND TO PHL ON A VECTOR DSNDING TO 6000 FT. APCH CTLR ISSUES TURN L IMMEDIATELY INSTRUCTIONS TO THE ACR SIMULTANEOUSLY WITH THE CREW RECEIVING A TCASII RA ALERT TO DSND. EVASIVE ACTION WAS NECESSARY AND A POSSIBLE OPERROR OCCURRED.

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ACR X WAS INBOUND TO PHL ON THE BUNTS ONE ARR. AFTER BUNTS INTXN; FLT X WAS DSNDED FROM 8000 FT TO 6000 FT AND GIVEN VECTOR HDG 100 DEGS. PREVIOUS ACFT HAD COMPLAINED THAT 6000 FT WAS AT THE BASE OF SCATTERED TO BROKEN CLOUD DECK AND WAS A ROUGH RIDE. WHEN WE REACHED 6000 FT; WE AGREED AND ASKED PHL APCH (128.4) FOR 5000 FT WHEN AVAILABLE. SHE SAID IT WOULD BE 15 MI MORE TILL LOWER. WE WERE THEN TURNED TO HDG 170 DEGS. OUR RADIO SET-UP WAS ON LOC 108.95 (ILS RWY 27R) WITH 265 DEGS FOR THE BRIEFED APCH TO PHL. THERE IS NO VOR ON THE FIELD. WE COULD DETERMINE OUR RELATIVE POS TO PHL BY THE LOC DME AND MOSTLY VISUAL CONDITIONS BELOW. AS WE NEARED PHL HDG 170 DEGS; A PERIOD OF EXCESSIVE COMS AND XMISSION OVERLAPS STARTED TO OCCUR. WE HEARD INSTRUCTIONS FOR SOMEONE TO TURN TO 090 DEGS; BUT THERE WAS NO IDENTIFIABLE CALL SIGN. OUR LOCATION WAS 5 DME NE OF PHL ARPT. THE FO MADE A COUPLE ATTEMPTS TO VERIFY WHO THE INSTRUCTIONS WERE FOR; BUT WITH NO RESPONSE. AT THIS TIME SEVERAL EVENTS HAPPENED WITHIN SECONDS. APCH FINALLY IDENTED 'ACR X; TURN IMMEDIATELY TO 070 DEGS AND MAKE IT A TIGHT TURN.' I; THE CAPT FLYING; TURN OFF THE AUTOPLT AND BANK 40 DEGS L TO COMPLY. AS THIS IS HAPPENING; A YELLOW TARGET ON TCASII HAS APPEARED AT 1 O'CLOCK POS; +500 FT AND CLOSING. IT APPEARS IMC ABOVE US. THE TARGET IS APCHING US; JUST AS WE HAVE CLICKED OFF THE AUTOPLT AND STARTED THE TIGHT TURN. TCASII NOW IDENTS THE TARGET AS CONVERGING RED AND ISSUES AN RA; 'DSND; DSND.' I IMMEDIATELY COMPLIED AND DSNDED. I HAD SEEN +300 FT ON THE RED TARGET IN THE BRIEF TIME THAT I HAD TO SCAN AND STILL EXECUTE THE TIGHT TURN. THE FO TOLD APCH CTL THAT WE WERE DSNDING FOR AN RA. SHE SAID THE TARGET WAS VFR AND NOT IN CONFLICT. (SHE HAD NEVER PREVIOUSLY IDENTED THAT TARGET AS APCHING US. BESIDES; IT WAS IMC ABOVE US.) THIS DID NOT AGREE WITH OUR COCKPIT TCASII. SHE SAID THAT SHE WANTED US BACK AT 6000 FT AND WE CLBED BACK UP. WE WERE HANDED OFF TO THE FINAL CTLR AND LANDED WITHOUT INCIDENT ON RWY 27R AT PHL. ONCE DURING THIS COM CONFUSION; A LULL OCCURRED. BOTH THE FO AND I HEARD HER STATE THAT SHE HAD BEEN OFF ON THE LAND LINE.