WDB TAKES EVASIVE ACTION ON ILS FINAL IN RESPONSE TO A TCASII RA CAUSED BY AN INTRUDER IN CLASS B AIRSPACE.

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ON AUG/XX/94; I WAS THE CAPT IN COMMAND OF FLT FROM DFW TO BOS. MY ACFT WAS A BOEING 767-232. FLT OP WAS NORMAL UNTIL WE RECEIVED AN 'RA' FROM OUR TCASII WHILE ON FINAL APCH TO RWY 4R AT BOSTON LOGAN INTL ARPT; NECESSITATING A CLB FROM 3000 FT MSL TO 3500 FT MSL. APPROX TIME OF THE 'RA' WAS XA09 LCL TIME. NOT LONG AFTER INTERCEPTING THE RWY 4R LOC AT 3000 FT MSL AND BEING CLRED FOR THE APCH; APCH CTL POINTED OUT TFC TO US AT OUR 10 O'CLOCK POS HDG SE AT 2800 FT AND UNCONFIRMED. NO SOONER THAN THE TIME IT TOOK TO ACKNOWLEDGE THE XMISSION; WE RECEIVED A TCASII 'TA' SHOWING A TARGET AT THAT POS AND 2800 FT. I WAS UNABLE TO FIND THE TFC IN THE NIGHT LIGHTS OF BOSTON AND RETURNED MY ATTN TO FLYING THE ACFT. WITHIN A MATTER OF SECONDS; WE RECEIVED THE TCASII 'RA' TO CLB AND BOTH THE FO AND I AGGRESSIVELY INITIATED A CLB IN RESPONSE TO THE 'RA.' AT 3500 FT MSL THE TCASII ADVISED US WE WERE CLR OF TFC. WE ESTIMATE OUR SEPARATION FROM THE TFC TO HAVE BEEN 500 FT. WE WERE THEN RECLRED FOR THE APCH TO RWY 4R AND COMPLETED THE APCH TO A LNDG. I LATER CALLED APCH CTL BY PHONE AND SPOKE WITH THE SUPVR. HE SAID THE TARGET POPPED UP ON THE CTLR'S SCREEN AT 2500 FT AND THEN SHOWED A CLB TO 2800 FT. AT THAT TIME THE CTLR ADVISED US AND WE RESPONDED TO THE 'RA.' THE SUPVR SAID THE TARGET WAS OUTSIDE THE 10 MI ARC AND THEY HAD NO RADIO CONTACT WITH HIM.