B757 ENCOUNTERS HELI TFC SAUNTERING THROUGH THE APCH PATH TO RWY 22 AT LGA AND RESPONDS TO RESULTING TCASII RA BELOW 1000 FT.

Narrative

FLT WAS CLRED FOR AN ILS RWY 22 APCH (LGA) IN VMC. AT APPROX 1800 FT MSL ON GS; THE TWR CALLED HELI TFC AT 1-2 O'CLOCK POS AT 500 FT MSL XING R TO L; AND THAT THE HELI HAD US IN SIGHT. AT APPROX 1000 FT MSL; WE GOT A TCASII TA ALERT FOLLOWED IN 1-2 SECONDS WITH A TCASII RA. WE DID NOT HAVE A VISUAL WITH THE TFC. THE AUTOPLT WAS DISCONNECTED AND A TCASII ORDERED CLB (1000-1300 FPM) WAS INITIATED. SHORTLY AFTER ESTABLISHING OUR CLB; THE RA CHANGED TO A TA AND THEN SIMPLY TO A TCASII TARGET. THE ACFT WAS MANUALLY FLOWN BACK TO GS AND AT 500 FT MSL WAS STABILIZED; ON SPD AND LINED UP. THE HELI WAS NEVER SEEN BUT PASSED 400 FT BENEATH US WITH MINIMAL LATERAL SEPARATION (ACCORDING TO TCASII). LGA TWR TOLD US THAT THE HELI HAD US IN SIGHT AND THAT THE TWR HAD BOTH THE HELI AND US IN SIGHT. IT WAS NOT A COMFORTABLE SIT. IN MY OPINION; THE HELI SHOULD HAVE BEEN TOLD TO CROSS THE ILS RWY 22 APCH COURSE 'BTWN' ARRIVING ACFT 'OR' FURTHER N OF THE ARPT. THAT WOULD HAVE PROVIDED MORE VERT SEPARATION BTWN ACFT AND AVOID THE POTENTIAL FOR A TCASII RA.