LTT ON VECTORS FOR APCH GIVEN WRONG VECTOR; MEANT FOR ANOTHER ACFT. QUESTIONS CTLR; GIVEN VECTOR BACK TO PREVIOUS HDG. TCASII VISUAL HELPED DETECT ERROR.

Narrative

I WAS PF. HDG APPROX S (180 DEGS). JUST PAST PHL OF OUR L. LOTS OF TFC FOR 9R AND RWY 35 (WE ARE GOING TO RWY 35). GIVEN THE VECTOR BY PHILADELPHIA APCH; 'ACR TURN L 030.' I THOUGHT THIS WAS A STRANGE VECTOR; BECAUSE WE DIDN'T GET A SQUARE BASE LEG AND I KNEW THIS WAS A TIGHT VECTOR TO KEEP SPACING ON TFC BEHIND US. THE CAPT REPLIED WITH 'ACR-IDENT; L TO 030.' NO REPLY FROM THE CTLR. I IMMEDIATELY BROUGHT THIS TO THE ATTN OF THE CAPT BY STATING SOMETHING LIKE 'THAT'S A STRANGE VECTOR FOR WHERE WE ARE.' HE RESPONDED WITH 'YEAH.' HE ALSO POINTED OUT TFC (ON TCASII AND VISUALLY) THAT WE MIGHT BE FOLLOWING. (BAD ASSUMPTION). THERE WAS STILL 1 MORE ACFT AHEAD OF US. I TURNED TO 030. I QUESTIONED THE CAPT AGAIN; AND ASKED HIM TO CONFIRM OUR HDG. AFTER A BRIEF DISCUSSION; HE CALLED ON THE RADIO AND SAID SOMETHING LIKE; 'ACR- IDENT HAS THE FIELD;' WHICH I THOUGHT WAS RATHER AMBIGUOUS. THAT WASN'T THE QUESTION I WOULD HAVE ASKED. I DON'T BELIEVE THE CTLR ACKNOWLEDGED. NOW I WAS IN A PREDICAMENT OF DIDN'T WANT TO GAR' THE CAPT; AND GET ON THE RADIO AND SAY 'DO YOU WANT ACR-ID ON A 030 HDG?' IT WASN'T MY JOB TO HANDLE THE RADIOS; AND HE MIGHT GET ANNOYED. BUT IT WAS LOOKING MORE AND MORE LIKE THE VECTOR WAS INCORRECT. WE WERE PARALLELING 2 AIRPLANES OFF OUR R. AND JUST BEFORE I MADE MY RADIO CALL; I SPOTTED AN AIRPLANE ON TCASII APCHING FROM OUR 11 O'CLOCK POS AND APPROX 5-6 MI. THE TCASII ACFT WAS THE FINAL STRAW; I CALLED ATC AND STATED 'DO YOU WANT ACR-IDENT ON A 030 HDG?' HE SAID NO; GO BACK TO 180 DEG. I IMMEDIATELY TURNED. THE CTLR THEN ASKED IF ACR XY WAS ON A 030 HDG AND THEY SAID NO; THEY WERE NEVER TOLD TO GO TO THAT HDG. I THINK THE BIGGEST FACTOR WAS THE CTLR'S INCORRECT VECTOR TO US. I DON'T THINK THE CAPT HELPED BY ASKING THE WRONG QUESTION. I BELIEVE HE WAS TRYING TO JOG THE MEMORY OF THE CTLR AND IT DIDN'T WORK.