Narrative:

I issued air carrier X a descent clearance to 8000 ft MSL. As air carrier X approached las he came within 5 NM of small aircraft Y, a cessna 172, level at 7500 ft MSL. I passed traffic to X. No response was received from X. I reissued the traffic call and observed air carrier X descending through 7600 ft MSL. Air carrier X advised me that he had received an RA, and it commanded a descent. Air carrier X then descended through the altitude of Y and leveled at 7400 ft MSL. In a controled environment such as a class B airspace, the only thing a TCASII can do is cause confusion and trouble. Air carrier X and cessna Y came within 2 - 2 1/2 NM. No visual separation was used. TCASII in an advisory role would be ok. We don't need 2 controllers issuing conflicting instructions. It can only lead to disaster!

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Original NASA ASRS Text

Title: ACR X TCASII RA NON ADHERENCE TO ATC CLRNC HAD LTSS FROM SMA Y IN TCA CLASS B AIRSPACE.

Narrative: I ISSUED ACR X A DSCNT CLRNC TO 8000 FT MSL. AS ACR X APCHED LAS HE CAME WITHIN 5 NM OF SMA Y, A CESSNA 172, LEVEL AT 7500 FT MSL. I PASSED TFC TO X. NO RESPONSE WAS RECEIVED FROM X. I REISSUED THE TFC CALL AND OBSERVED ACR X DSNDING THROUGH 7600 FT MSL. ACR X ADVISED ME THAT HE HAD RECEIVED AN RA, AND IT COMMANDED A DSCNT. ACR X THEN DSNDED THROUGH THE ALT OF Y AND LEVELED AT 7400 FT MSL. IN A CTLED ENVIRONMENT SUCH AS A CLASS B AIRSPACE, THE ONLY THING A TCASII CAN DO IS CAUSE CONFUSION AND TROUBLE. ACR X AND CESSNA Y CAME WITHIN 2 - 2 1/2 NM. NO VISUAL SEPARATION WAS USED. TCASII IN AN ADVISORY ROLE WOULD BE OK. WE DON'T NEED 2 CTLRS ISSUING CONFLICTING INSTRUCTIONS. IT CAN ONLY LEAD TO DISASTER!

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.