AN ACR CREW REPORTS RESPONDING TO A TCAS RA ON APCH TO EWR AFTER ANOTHER ACFT FAILED TO RESPOND TO AN ATC VECTOR.

Narrative

WHILE BEING RADAR VECTORED FOR THE VISUAL APCH TO RWY 4R EWR; THE ACFT WAS LEVEL AT 4000 FT ON A HDG OF 170 DEGS AS ASSIGNED BY NEW YORK TRACON. THE CREW NOTICED A TCAS TARGET APCHING FROM THE 1 O'CLOCK POS ALSO AT 4000 FT AND LESS THAN 5 NM. I OBTAINED VISUAL CONTACT WITH THE OTHER ACFT AND CONFIRMED THAT IT WAS HEADING DIRECTLY FOR US AT OUR ALT. AT APPROX THE SAME TIME; NEW YORK TRACON ISSUED A TFC ALERT AND INSTRUCTED US TO 'CLB IMMEDIATELY' TO 5000 FT. THE CAPT WAS FLYING AND DISENGAGED THE AUTOPLT TO COMPLY AT ABOUT THE SAME TIME TCAS ISSUED A CLB RA. AS OUR ACFT CLBED THROUGH APPROX 4600 FT; I WITNESSED THE OTHER ACFT (MEDIUM SIZED BIZJET) MAKE A LEVEL TURN AWAY FROM US AT A RANGE OF LESS THAN 1/2 MI. CLR OF CONFLICT WAS ANNOUNCED BY TCAS AND APCH AND LNDG WERE ACCOMPLISHED UNEVENTFULLY. ATC'S EXPLANATION OF THE EVENT WAS THAT THE OTHER ACFT 'TOOK A BAD VECTOR FROM ANOTHER CTLR.' TCAS WORKED AS ADVERTISED BUT BOTH CAPT AND I WERE SURPRISED AT HOW CLOSE OTHER ACFT APCHED BEFORE THE ACTIVATION OF THE RA EVENT.