CAPT OF A CANADAIR REGIONAL JET; CL65; DSNDED IN RESPONSE TO A TCASII RA RESULTING IN A CONFLICT WITH ANOTHER ACFT IN LEVEL FLT 2000 FT BELOW. FLC SUSPECTS THAT THE TCASII HAD GIVEN A FALSE WARNING SINCE ARTCC CTLR ADVISED OF NO KNOWN CONFLICTING TFC.

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WHILE AT LEVEL CRUISE; ON AUTOPLT; AT FL330 ON J51 INBOUND TO SAV; AT APPROX XX27Z; WE EXPERIENCED A 'DSND; DSND' AURAL WARNING ALONG WITH RED 'DSND' MESSAGES ON BOTH PRIMARY FLT DISPLAYS. I REACTED IMMEDIATELY BY DISENGAGING THE AUTOPLT AND PUSHED OVER. AT THAT VERY MOMENT; THE AURAL 'DSND' WARNING CHANGED TO AN AURAL 'TFC; TFC' ADVISORY WITH AMBER 'TFC' MESSAGES DISPLAYED ON BOTH PRIMARY FLT DISPLAYS. ATC 'CALLED' AND WE SPOTTED OPPOSITE DIRECTION TFC AT FL310. I LEVELED THE ACFT IMMEDIATELY LOSING LESS THAN 300 FT AND STARTED A CLB BACK TO FL330. I RPTED THE RA TO ATC. THE CTLR WAS UNAWARE OF ANY POSSIBLE CONFLICT. MY TRIP TERMINATED AT RDO. ON RETURN HOME; I REHASHED THE EVENT AND WENT OVER THE SYS. I THEN BECAME AWARE THAT THE RA 'DSND' COMMANDS WERE WITHOUT GUIDANCE COMMANDS. COMING TO THE CONCLUSION THAT THE 'DSND WARNING' WAS POSSIBLY SPURIOUS AND POTENTIALLY DANGEROUS; I CALLED OUR MAINT CTL DUTY OFFICER AND PASSED ON THE INFO AND MY CONCERNS TO HIM. HE AGREED TO HAVE MAINT AT RDO DO A SYS CHK.