Narrative:

Inbound to lga on minks 1 arrival, 12000 ft, received traffic notification from approach frequency 125.45 -- could not see traffic. Finally received a descending RA. Notified approach control that we were responding to an RA, but controller's response was 'do not descend.' we followed RA to about 250 ft below assigned altitude, when TCASII gave a 'monitor vertical speed.' when that ceased, we returned to assigned altitude. What concerns me is the controller's issuing instructions to ignore TCASII. We could not find the traffic, we responded to an RA, we notified ATC, and returned to altitude as soon as possible. These are the rules as I understand them. What was obviously confusing was receiving conflicting instructions from TCASII and ATC. I don't believe ATC should be giving instructions to ignore an RA. Callback conversation with reporter revealed the following information: reporter verified that he was in N90 airspace, in the immediate vicinity of minks intersection, cleared direct lga. The pilot did not see either aircraft above or below. The aircraft above, he thought, came within 600 ft vertical, possibly a VFR aircraft. Only 1 time before had a controller asked him not to react to TCASII, but that was right after the TCASII system was brought into service. The pilot was aware of the 'box' a TCASII RA can put the controller into -- seeing something happen, but not being able to do much about it.

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Original NASA ASRS Text

Title: MD80 FLC INITIATE TCASII RA DSCNT EVASIVE ACTION, AND EVASIVE MANEUVER IS CHALLENGED BY APCH CTLR. PLT CONCERNED ABOUT RECEIVING CONFLICTING INFO, TCASII AND ATC.

Narrative: INBOUND TO LGA ON MINKS 1 ARR, 12000 FT, RECEIVED TFC NOTIFICATION FROM APCH FREQ 125.45 -- COULD NOT SEE TFC. FINALLY RECEIVED A DSNDING RA. NOTIFIED APCH CTL THAT WE WERE RESPONDING TO AN RA, BUT CTLR'S RESPONSE WAS 'DO NOT DSND.' WE FOLLOWED RA TO ABOUT 250 FT BELOW ASSIGNED ALT, WHEN TCASII GAVE A 'MONITOR VERT SPD.' WHEN THAT CEASED, WE RETURNED TO ASSIGNED ALT. WHAT CONCERNS ME IS THE CTLR'S ISSUING INSTRUCTIONS TO IGNORE TCASII. WE COULD NOT FIND THE TFC, WE RESPONDED TO AN RA, WE NOTIFIED ATC, AND RETURNED TO ALT ASAP. THESE ARE THE RULES AS I UNDERSTAND THEM. WHAT WAS OBVIOUSLY CONFUSING WAS RECEIVING CONFLICTING INSTRUCTIONS FROM TCASII AND ATC. I DON'T BELIEVE ATC SHOULD BE GIVING INSTRUCTIONS TO IGNORE AN RA. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR VERIFIED THAT HE WAS IN N90 AIRSPACE, IN THE IMMEDIATE VICINITY OF MINKS INTXN, CLRED DIRECT LGA. THE PLT DID NOT SEE EITHER ACFT ABOVE OR BELOW. THE ACFT ABOVE, HE THOUGHT, CAME WITHIN 600 FT VERT, POSSIBLY A VFR ACFT. ONLY 1 TIME BEFORE HAD A CTLR ASKED HIM NOT TO REACT TO TCASII, BUT THAT WAS RIGHT AFTER THE TCASII SYS WAS BROUGHT INTO SVC. THE PLT WAS AWARE OF THE 'BOX' A TCASII RA CAN PUT THE CTLR INTO -- SEEING SOMETHING HAPPEN, BUT NOT BEING ABLE TO DO MUCH ABOUT IT.

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.