Narrative:

Air carrier X was descending for landing at bwi. We were issued clearance to 5000 ft. At 6500 ft we're instructed to level at 6000 ft due to traffic at 12 O'clock, 8 mi at 5500 ft (was not in visual sight). After approximately 45 seconds TCASII issued an RA to climb plus 1500 to 2000 FPM. We climbed to 6500 ft and TCASII issued a clear of conflict. We then spotted aircraft to our 2-3 O'clock at distances described on front. It was a cpr Y, light transport. Although possibly no conflict existed, per our operations manual, we are not allowed to disregard TCASII RA's. I was instructed to call bwi TRACON where I was questioned about the TCASII instruction and was told incident would be written up. I would suggest controllers be more informed about TCASII and how they operate.

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Original NASA ASRS Text

Title: ACR X NON ADHERENCE TO ATC CLRNC TCASII TA RA CLB EVASIVE ACTION TAKEN FROM VFR CPR Y. PLTDEV.

Narrative: ACR X WAS DSNDING FOR LNDG AT BWI. WE WERE ISSUED CLRNC TO 5000 FT. AT 6500 FT WE'RE INSTRUCTED TO LEVEL AT 6000 FT DUE TO TFC AT 12 O'CLOCK, 8 MI AT 5500 FT (WAS NOT IN VISUAL SIGHT). AFTER APPROX 45 SECONDS TCASII ISSUED AN RA TO CLB PLUS 1500 TO 2000 FPM. WE CLBED TO 6500 FT AND TCASII ISSUED A CLR OF CONFLICT. WE THEN SPOTTED ACFT TO OUR 2-3 O'CLOCK AT DISTANCES DESCRIBED ON FRONT. IT WAS A CPR Y, LTT. ALTHOUGH POSSIBLY NO CONFLICT EXISTED, PER OUR OPS MANUAL, WE ARE NOT ALLOWED TO DISREGARD TCASII RA'S. I WAS INSTRUCTED TO CALL BWI TRACON WHERE I WAS QUESTIONED ABOUT THE TCASII INSTRUCTION AND WAS TOLD INCIDENT WOULD BE WRITTEN UP. I WOULD SUGGEST CTLRS BE MORE INFORMED ABOUT TCASII AND HOW THEY OPERATE.

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.