Narrative:

Cleared to descend to 10000 ft MSL. At about 11000 ft MSL, TCASII RA occurred with 'increase descent' command to 1500- 2000 ft down vertical speed. Approach called out traffic climbing to 9000 ft. TCASII commanded 'increase descent' to 2500 ft plus vertical speed down and 'crossing descent.' as PF (on autoplt), I followed the TCASII commands, descended through 10000 ft in response to the TCASII RA. Visually sighted the traffic an air carrier B medium large transport at 2 O'clock and approximately 500 ft low. TCASII RA was still commanding a descent through air carrier B altitude. Disconnected the autoplt and stopped the descent at about 9300 ft MSL and air carrier B passed under us. If we had continued to follow TCASII RA we would have hit air carrier B. Returned to 10000 ft MSL, the altitude we were cleared to. Note: the TCASII commands were so loud they interfered with hearing lax approach and also with pilot-to-pilot communication.

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Original NASA ASRS Text

Title: A TCASII RA LEADS AN MLG TOWARD A COLLISION RATHER THAN AWAY FROM IT.

Narrative: CLRED TO DSND TO 10000 FT MSL. AT ABOUT 11000 FT MSL, TCASII RA OCCURRED WITH 'INCREASE DSCNT' COMMAND TO 1500- 2000 FT DOWN VERT SPD. APCH CALLED OUT TFC CLBING TO 9000 FT. TCASII COMMANDED 'INCREASE DSCNT' TO 2500 FT PLUS VERT SPD DOWN AND 'XING DSCNT.' AS PF (ON AUTOPLT), I FOLLOWED THE TCASII COMMANDS, DSNDED THROUGH 10000 FT IN RESPONSE TO THE TCASII RA. VISUALLY SIGHTED THE TFC AN ACR B MLG AT 2 O'CLOCK AND APPROX 500 FT LOW. TCASII RA WAS STILL COMMANDING A DSCNT THROUGH ACR B ALT. DISCONNECTED THE AUTOPLT AND STOPPED THE DSCNT AT ABOUT 9300 FT MSL AND ACR B PASSED UNDER US. IF WE HAD CONTINUED TO FOLLOW TCASII RA WE WOULD HAVE HIT ACR B. RETURNED TO 10000 FT MSL, THE ALT WE WERE CLRED TO. NOTE: THE TCASII COMMANDS WERE SO LOUD THEY INTERFERED WITH HEARING LAX APCH AND ALSO WITH PLT-TO-PLT COM.

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.