A WDB ACR CREW FAILED TO TURN TO A NEWLY ASSIGNED HDG IN THE JFK TFC PATTERN.

Narrative

WHILE BEING VECTORED TO FINAL APCH FOR AN ILS TO 31L; APCH CTL GAVE A L TURN TO A 270 DEG HDG. THE CAPT WAS FLYING; I (THE FO) ANSWERED AND READ BACK THE HDG. I LOOKED UP AND SAW THE CAPT SELECT THE HDG ON THE AFS PANEL ON THE GLARESHIELD. THE AUTOPLT WAS ON. THE CTLR THEN TOLD US TO PREPARE FOR AN APCH TO 31R NOW. WHILE I WAS DIGGING OUT THE NEW APCH PLATE AND RETUNING ALL RADIOS; GETTING IDENTS; SETTING NEW DH'S; ETC; THE CTLR CALLED BACK AND ASKED US IF WE WERE ON OUR ASSIGNED 270 DEG HDG? WE BOTH LOOKED AT THE AFS PANEL WHICH CTLS THE AUTOPLT AND SAW 270 DEG SET BUT THE AUTOPLT FAILED TO TURN TO THIS HDG. WHILE I WAS TRYING TO ANSWER HIM; HE NOW GAVE US A R TURN TO 090 DEG HDG TO TAKE US OUT OF POS AND BRING US BACK AROUND FOR ANOTHER TRY AT 31L AGAIN. I AGAIN HAD TO RETUNE EVERYTHING BACK TO THE ORIGINAL 31L DATA. I GUESS FROM NOW ON I (THE FO) WILL NOT ONLY HAVE TO VERIFY THE SET NUMBERS ARE SET; BUT WATCH AND VERIFY THE SET NUMBERS ENGAGE WHILE ON AUTOPLT AND THE PLANE STARTS TO DO WHAT HAS BEEN SELECTED. A 2 MAN WIDE-BODY COCKPIT IN TERMINAL APCH PHASES TO AN ARPT SUCH AS JFK IS A BUSY PLACE. EACH PLT MUST NOT ONLY VERIFY EACH OTHER BUT THE AUTOPLT ALSO WHILE ON. HAD THE CTLR NOT KEPT SWITCHING RWYS ON US; MAKING ME SWITCH AND RETUNE EVERYTHING; THEN MAYBE I COULD HAVE DONE A BETTER MONITORING JOB AND WOULD HAVE NOTICED THE AUTOPLT FAILING TO ENGAGE AND START TURNING BEFORE THE APCH CTLR DID AND 30-45 SECONDS LATER INQUIRING WITH US ABOUT OUR HDG.