Narrative:

TCASII annunciated a TA, then RA, followed by aural 'descend crossing descend.' the vsi commanded a 1500 FPM descent rate which was executed. At 27500 ft, TCASII announced 'clear of conflict.' ATC was notified while descending. ATC then told us to turn 20 degrees left for spacing on lower traffic at 27000 ft. The mandatory RA was for traffic descending from above us to 29000 ft. This traffic leveled at 29000, however, it must have been in a high rate of descent at this point in time. This unnecessary mandatory deviation placed us in conflict with another aircraft. Additionally, the aural TCASII commands are very loud and block ATC transmissions. TCASII system needs more perfecting.

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Original NASA ASRS Text

Title: AN ACR MLG CREW HAD A TCASII RA DEMANDING A DSCNT. THE RPTING CREW DSNDED INTO ANOTHER ACFT'S AIRSPACE.

Narrative: TCASII ANNUNCIATED A TA, THEN RA, FOLLOWED BY AURAL 'DSND XING DSND.' THE VSI COMMANDED A 1500 FPM DSCNT RATE WHICH WAS EXECUTED. AT 27500 FT, TCASII ANNOUNCED 'CLR OF CONFLICT.' ATC WAS NOTIFIED WHILE DSNDING. ATC THEN TOLD US TO TURN 20 DEGS L FOR SPACING ON LOWER TFC AT 27000 FT. THE MANDATORY RA WAS FOR TFC DSNDING FROM ABOVE US TO 29000 FT. THIS TFC LEVELED AT 29000, HOWEVER, IT MUST HAVE BEEN IN A HIGH RATE OF DSCNT AT THIS POINT IN TIME. THIS UNNECESSARY MANDATORY DEV PLACED US IN CONFLICT WITH ANOTHER ACFT. ADDITIONALLY, THE AURAL TCASII COMMANDS ARE VERY LOUD AND BLOCK ATC TRANSMISSIONS. TCASII SYS NEEDS MORE PERFECTING.

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.