Narrative:

While working kennedy departure radar in nov 1996, at XX00L a VFR aircraft small aircraft Y, a PA28A with operating mode C, was cleared through the kennedy class B airspace swbound at 4500 ft. Air carrier X, a H-B767 with TCASII departed runway 31L at jfk and was restr to 4000 ft. Air carrier X was level at 4000 ft and turned nebound. Traffic was exchanged between air carrier X and small aircraft Y. The 2 radar targets merged and when they separated I issued a climb to air carrier X. A few mins, and about 20 mi, later air carrier X asked me if the VFR that he had crossed had operating mode C. I replied affirmative and air carrier X replied that he had received a TCASII RA which had told him to climb. I verified that this is what he was instructed to do and he confirmed that the RA was to climb. I told him that I was glad he did not follow the RA and that he should report the equipment to his company. The B767 crossed directly beneath the VFR PA28 with appropriate separation. A climb by the B767 at this time could have been disastrous. The air carrier X pilot was out over the ocean at night with no horizon to help him judge the altitude of the VFR aircraft. Only his faith in the traffic call I had issued prevented a mishap. This is not the first time I have heard of TCASII issuing erroneous RA's but this is one case where it could have been fatal.

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Original NASA ASRS Text

Title: A DEPARTING ACR B767 IS RESTR TO 4000 FT DUE TO VFR CLASS B TFC AT 4500 FT. TFC WAS ISSUED BY THE CTLR AND THE B767 CROSSED BELOW THE VFR ACFT. THE B767 PLT MENTIONED THAT THEY HAD RECEIVED A TCASII RA TO CLB, BUT REMAINED AT 4000 FT. THE CTLR CLAIMS THAT THE PLT'S ACTION TO REMAIN AT 4000 FT PREVENTED A MISHAP.

Narrative: WHILE WORKING KENNEDY DEP RADAR IN NOV 1996, AT XX00L A VFR ACFT SMA Y, A PA28A WITH OPERATING MODE C, WAS CLRED THROUGH THE KENNEDY CLASS B AIRSPACE SWBOUND AT 4500 FT. ACR X, A H-B767 WITH TCASII DEPARTED RWY 31L AT JFK AND WAS RESTR TO 4000 FT. ACR X WAS LEVEL AT 4000 FT AND TURNED NEBOUND. TFC WAS EXCHANGED BTWN ACR X AND SMA Y. THE 2 RADAR TARGETS MERGED AND WHEN THEY SEPARATED I ISSUED A CLB TO ACR X. A FEW MINS, AND ABOUT 20 MI, LATER ACR X ASKED ME IF THE VFR THAT HE HAD CROSSED HAD OPERATING MODE C. I REPLIED AFFIRMATIVE AND ACR X REPLIED THAT HE HAD RECEIVED A TCASII RA WHICH HAD TOLD HIM TO CLB. I VERIFIED THAT THIS IS WHAT HE WAS INSTRUCTED TO DO AND HE CONFIRMED THAT THE RA WAS TO CLB. I TOLD HIM THAT I WAS GLAD HE DID NOT FOLLOW THE RA AND THAT HE SHOULD RPT THE EQUIP TO HIS COMPANY. THE B767 CROSSED DIRECTLY BENEATH THE VFR PA28 WITH APPROPRIATE SEPARATION. A CLB BY THE B767 AT THIS TIME COULD HAVE BEEN DISASTROUS. THE ACR X PLT WAS OUT OVER THE OCEAN AT NIGHT WITH NO HORIZON TO HELP HIM JUDGE THE ALT OF THE VFR ACFT. ONLY HIS FAITH IN THE TFC CALL I HAD ISSUED PREVENTED A MISHAP. THIS IS NOT THE FIRST TIME I HAVE HEARD OF TCASII ISSUING ERRONEOUS RA'S BUT THIS IS ONE CASE WHERE IT COULD HAVE BEEN FATAL.

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.