PHL APCH CTLR DSNDS A B767 INTO A HELI; RESULTING IN AN RA.

Narrative

DURING DSCNT INTO PHL ON A DIRECT TO BUNTS ROUTING; WE WERE TOLD TO DSND AND MAINTAIN 6000 FT ON AN ALTIMETER OF 29.45. BOTH THE CAPT (PF) AND I (CAPT FLYING AS A FO AND PLT MONITORING) HEARD THE DSCNT CLRNC ALT OF 6000 FT AND VERIFIED IT IN THE MCP ALT WINDOW. PASSING 8300 FT OR SO; THE CTLR TOLD US THAT THERE WOULD BE TFC; A HELI AT 11 O'CLOCK AND 6000 FT. WE NOTED IT AND STARTED TO LOOK FOR IT BOTH VISUALLY AND WITH THE TCAS. ALSO; TO EACH OTHER; NOTING THAT IT WAS GOING TO BE AT THE SAME ALT; FIGURING IT WAS GOING OUT OF OUR PATH ON A DIFFERENT DIRECTION. WE PICKED IT UP ON THE TCAS AT ABOUT 12 MI AND ABOUT THE TIME THAT WE LEVELED AT 6000 FT. WE MENTIONED IT TO EACH OTHER AGAIN AND THOUGHT WE HAD IT IN SIGHT. I COUNTED OFF THE MI VERBALLY. ALSO; WE STARTED DISCUSSING WHETHER THIS WAS BECOMING A CONFLICT; AND WONDERING WHY WE HAD BEEN GIVEN THIS CLRNC. JUST AS I (PLT MONITORING) WAS KEYING THE MIKE TO VERIFY THE CTLR'S INSTRUCTIONS; WE GOT THE 'TFC' ALERT; RAPIDLY FOLLOWED BY A 'DSCNT RA' FROM THE TCAS. WE COMPLIED IMMEDIATELY AND I TOLD THE CTLR OF OUR RA AND MANEUVERING. HE THEN RESPONDED THAT HE CLAIMED TO HAVE GIVEN US A DSCNT ONLY TO 7000 FT. I REPLIED THAT WE HAD BEEN GIVEN 6000 FT. HE DIDN'T ARGUE. BOTH THE CAPT AND I AGREED THAT 6000 FT WAS THE CLRNC THAT WE WERE GIVEN AND STATED IT TO EACH OTHER. I QUERIED THE CTLR IF HE WANTED US TO CLB UP TO 7000 FT AFTER THE RA; AT WHICH TIME HE TOLD US TO CONTINUE DOWN TO 3000 FT. NOTHING MORE WAS SAID BY ATC PHL APCH; AND THE REST OF THE APCH AND LNDG WAS UNEVENTFUL. SUPPLEMENTAL INFO FROM ACN 690386: ACR X CHKED IN DSNDING OVER BUNTS TO 10000 FT. AFTER XING BUNTS; I DSNDED HIM TO 7000 FT (AFTER TAPE REVIEW IT APPEARS I DSNDED THE ACFT TO 6000 FT. I ISSUED TFC TO ACR X REF ACFT Y SWBOUND AT 6000 FT. ACR X ADVISED THAT HE WAS RESPONDING TO RA AND I INSTRUCTED THE PLT TO CLB TO 7000 FT.