ACR X HAD LTSS FROM ACFT Y. SYS ERROR. TCASII TA RA EVASIVE ACTION TAKEN.

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ACR X TCASII TA AT 15 MI; 12:30 POS 900 DSNDING. THIS TURNED INTO A RA AT 6 MI 500 ABOVE DSNDING. ACR X WAS COMMANDED VERBALLY TO DSND AND 1 VSI GREEN ARC WAS 1600 TO 1900 FPM DOWN. COMMENCED DSCNT AND ADVISED ATC OF RA AND DSCNT WHO RESPONDED WITH CLR TO DSND. CLR OF CONFLICT WAS COMMANDED AT AN ALT OF FL270. A 1000 FT DSCNT. TCAS TARGET PASSED ABOVE US ON TCAS SCOPE INDICATING 300 FT ABOVE AND ABOUT 1/4 TO 1/2 MI TO THE R. ATC WAS CALLED AFTER CLR OF CONFLICT TO SEE IF THEY WANTED ME TO MAINTAIN FL270 OR CLB BACK TO FL280. NO ANSWER. CALLED SECOND TIME. WAS TOLD TO STANDBY. CALLED A SHORT TIME LATER AND WAS SWITCHED TO ANOTHER FREQ. TO ME THIS IS UNACCEPTABLE. I SUBMITTED THIS RPT BECAUSE OF THE FOLLOWING REASONS: THERE IS A GREAT LACK OF CONFIDENCE IN THE TCAS SYS WITH THE PLT GROUP. I WAS ONE OF THEM BUT I BELIEVE THIS SAVED A MID AIR COLLISION. TRAINING STANDARDS ARE NOT SET FOR TCAS SUCH AS MANDATORY SIMULATOR INSTALLATION AND APPROVED OPERATOR PROCS SUCH AS CAT II AND III APCHS.