Narrative:

While descending to 11000 ft, ATC called traffic at 10 O'clock. We called negative contact. ATC advised the traffic had us in sight. As we leveled at 11000 ft the TCASII called traffic and then climb climb, followed quickly by monitor vertical speed and do not descend. A G-2 passed 400 ft underneath us. We called ZBW after landing and were told he was on a VFR flight plan at 10500 ft, so there was legal separation. He still should have avoided passing 400 ft under a descending aircraft that had made it clear he was not in sight.

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Original NASA ASRS Text

Title: TCASII. VFR ACFT IN COM WITH ATC PASSED CLOSE AND UNDER ACR ACFT.

Narrative: WHILE DSNDING TO 11000 FT, ATC CALLED TFC AT 10 O'CLOCK. WE CALLED NEGATIVE CONTACT. ATC ADVISED THE TFC HAD US IN SIGHT. AS WE LEVELED AT 11000 FT THE TCASII CALLED TFC AND THEN CLB CLB, FOLLOWED QUICKLY BY MONITOR VERT SPD AND DO NOT DSND. A G-2 PASSED 400 FT UNDERNEATH US. WE CALLED ZBW AFTER LNDG AND WERE TOLD HE WAS ON A VFR FLT PLAN AT 10500 FT, SO THERE WAS LEGAL SEPARATION. HE STILL SHOULD HAVE AVOIDED PASSING 400 FT UNDER A DSNDING ACFT THAT HAD MADE IT CLR HE WAS NOT IN SIGHT.

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.