Narrative:

Approaching bos runway 4R night VMC on the visual approach. Just prior to crossing over the harbor on final approach, the TCASII momentarily alerted TA and then 1 second later to an RA for (what turned out to be) a police helicopter climbing left to right, crossing our bow co-altitude roughly 1 mi in front of our aircraft. As the 'climb' command was being blared into our cockpit, bos tower reported the helicopter as traffic (for the first time) and my copilot later remembered hearing it mentioned that the helicopter was said also to have reported our aircraft in sight. As the helicopter moved to our 1 O'clock position and no longer a factor we acquired it visually and discontinued the climb maneuver commanded by TCASII and salvaged the approach. A subsequent conversation with the tower supervisor elicited an apology on behalf of his subordinate for not reporting the traffic to us prior to TCASII doing so. Still, I have concerns about the policy in place. Regardless of whether the helicopter thinks he has us in sight (approachs were also being conducted to the parallel runway) I strongly object to the margin of safety being eroded by his being at our altitude as he crossed our extended runway centerline. Had he remained well below the GS until well clear of the approach corridor, there would have been no problem. Callback conversation with reporter revealed the following information: reporter advised the helicopter passed ahead approximately 1 mi at his altitude. The reporter was not sure about the timeliness of the TA, as the first officer later acknowledged that he heard the local controller advise that the helicopter had them in sight. Reporter's main concern is that ATC should not allow traffic to cross in front when on an ILS approach inside the OM, but should be forced under and below until traffic passes.

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Original NASA ASRS Text

Title: ON APCH TO BOS RWY 4R AT 1200 FT, A B737-800 FLT CREW RECEIVE A TCASII ALERT DUE TO HELI PASSING FLT PATH AHEAD AT SAME ALT.

Narrative: APCHING BOS RWY 4R NIGHT VMC ON THE VISUAL APCH. JUST PRIOR TO XING OVER THE HARBOR ON FINAL APCH, THE TCASII MOMENTARILY ALERTED TA AND THEN 1 SECOND LATER TO AN RA FOR (WHAT TURNED OUT TO BE) A POLICE HELI CLBING L TO R, XING OUR BOW CO-ALT ROUGHLY 1 MI IN FRONT OF OUR ACFT. AS THE 'CLB' COMMAND WAS BEING BLARED INTO OUR COCKPIT, BOS TWR RPTED THE HELI AS TFC (FOR THE FIRST TIME) AND MY COPLT LATER REMEMBERED HEARING IT MENTIONED THAT THE HELI WAS SAID ALSO TO HAVE RPTED OUR ACFT IN SIGHT. AS THE HELI MOVED TO OUR 1 O'CLOCK POS AND NO LONGER A FACTOR WE ACQUIRED IT VISUALLY AND DISCONTINUED THE CLB MANEUVER COMMANDED BY TCASII AND SALVAGED THE APCH. A SUBSEQUENT CONVERSATION WITH THE TWR SUPVR ELICITED AN APOLOGY ON BEHALF OF HIS SUBORDINATE FOR NOT RPTING THE TFC TO US PRIOR TO TCASII DOING SO. STILL, I HAVE CONCERNS ABOUT THE POLICY IN PLACE. REGARDLESS OF WHETHER THE HELI THINKS HE HAS US IN SIGHT (APCHS WERE ALSO BEING CONDUCTED TO THE PARALLEL RWY) I STRONGLY OBJECT TO THE MARGIN OF SAFETY BEING ERODED BY HIS BEING AT OUR ALT AS HE CROSSED OUR EXTENDED RWY CTRLINE. HAD HE REMAINED WELL BELOW THE GS UNTIL WELL CLR OF THE APCH CORRIDOR, THERE WOULD HAVE BEEN NO PROB. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR ADVISED THE HELI PASSED AHEAD APPROX 1 MI AT HIS ALT. THE RPTR WAS NOT SURE ABOUT THE TIMELINESS OF THE TA, AS THE FO LATER ACKNOWLEDGED THAT HE HEARD THE LCL CTLR ADVISE THAT THE HELI HAD THEM IN SIGHT. RPTR'S MAIN CONCERN IS THAT ATC SHOULD NOT ALLOW TFC TO CROSS IN FRONT WHEN ON AN ILS APCH INSIDE THE OM, BUT SHOULD BE FORCED UNDER AND BELOW UNTIL TFC PASSES.

Data retrieved from NASA's ASRS site as of July 2007 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.