Narrative:

While proceeding on the milton 8 arrival to lga at 11000 ft over lizzi intersection, we observed a target on TCASII. This target was descending opposite direction from a higher altitude. The aircraft descended to 11500 ft, leveled, then started another descent down in front of us to a point about 3 mi and 11200 ft MSL. The TCASII initially displayed and called out traffic, traffic. A very short time frame later, the TCASII commanded a traffic RA to descend. We followed the RA command and descended to must above 10000 ft MSL. We then advised ATC of the incident and asked what altitude he would like us to maintain. This intruder aircraft was apparently flying VFR in IFR in the cloud conditions. ATC did not advise us of the traffic, nor was the traffic in contact with ZNY. We never saw the aircraft visually.

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Original NASA ASRS Text

Title: TCASII RA.

Narrative: WHILE PROCEEDING ON THE MILTON 8 ARR TO LGA AT 11000 FT OVER LIZZI INTXN, WE OBSERVED A TARGET ON TCASII. THIS TARGET WAS DSNDING OPPOSITE DIRECTION FROM A HIGHER ALT. THE ACFT DSNDED TO 11500 FT, LEVELED, THEN STARTED ANOTHER DSCNT DOWN IN FRONT OF US TO A POINT ABOUT 3 MI AND 11200 FT MSL. THE TCASII INITIALLY DISPLAYED AND CALLED OUT TFC, TFC. A VERY SHORT TIME FRAME LATER, THE TCASII COMMANDED A TFC RA TO DSND. WE FOLLOWED THE RA COMMAND AND DSNDED TO MUST ABOVE 10000 FT MSL. WE THEN ADVISED ATC OF THE INCIDENT AND ASKED WHAT ALT HE WOULD LIKE US TO MAINTAIN. THIS INTRUDER ACFT WAS APPARENTLY FLYING VFR IN IFR IN THE CLOUD CONDITIONS. ATC DID NOT ADVISE US OF THE TFC, NOR WAS THE TFC IN CONTACT WITH ZNY. WE NEVER SAW THE ACFT VISUALLY.

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.