FLC OF ACR WDB ACFT DEVIATED FROM ASSIGNED ALT BECAUSE OF AN ACFT TCASII EQUIP ALERT.

Narrative

INITIAL CLRNC TO FL230 FOLLOWED BY CLRNC TO FL250. WHILE LEVEL AT FL250 AWAITING CLRNC TO CRUISING ALT I WAS LOOKING OUTSIDE WHEN TCASII GAVE A TA. I GLANCED AT THE TCASII THE TFC WAS 11 TO 11:30 (-19) 1900 FT BELOW US (I MAY NOT HAVE SEEN A MINUS SIGN THIS WAS HAPPENING FAST) AND DSNDING. IT APPEARED TO BE 10 MI AWAY AS I THOUGHT THE TCASII WAS ON A 40 MI RANGE BUT LATER LEARNED IT WAS ON 5 MI. WITHIN 2 SECONDS OF THE TA AN RA SOUNDED WITH A 2 WORD COMMAND WHICH I DID NOT HEAR CLRLY FOLLOWED BY THE WORD 'CLB.' I DISCONNECTED THE AUTOPLT AND INCREASED THE PITCH ATTITUDE AUTO THROTTLES BROUGHT THE PWR UP. THE CAPT WAS ABOUT TO ADVISE ATC OF OUR ACTIONS WHEN ATC ADVISED US TO 'MAINTAIN FL250.' HE ADVISED WE WERE RESPONDING TO AN RA AND CLBING. AT FL257 'CLB' CHANGED TO A COMMAND TO 'DSND.' THE ACFT REACHED FL258 PRIOR TO THE INITIATION OF THE DSCNT. AS SOON AS A RATE OF DSCNT WAS ESTABLISHED TCASII WAS SILENT AND WE LEVELED AT FL250. OAKLAND ADVISED OUR COMPANY THAT WE MISSED THE TFC LEVEL AT FL260 BY 1 MI AND 200 FT. TCASII PROVIDES US WITH APPARENTLY FALSE AND DISTRACTING WARNINGS ON A DAILY BASIS; AND NOW HAS COMMANDED US TO A NEAR MISS.