ACR HAS TCASII RA. RESPONDS WITH CLB.

Narrative

WE HAD ARRIVED IN THE ATL AREA AND WERE BEING VECTORED FOR OUR APCH; APCH CTL ADVISED US OF TFC AT 12 O'CLOCK AND WE INFORMED HIM THAT WE WERE IFR. WITHOUT GIVING ANY KIND OF TFC ALERT THE TCASII SYS ISSUED A RA WITH THE AURAL MESSAGE TO 'CLB; CLB; CLB'. IN ACCORDANCE WITH THE OPERATING PROC FOR OUR ACFT; THE AUTOPLT WAS DISCONNECTED AND A CLB INITIATED FROM THE ASSIGNED ALT OF 11000 FT. AFTER GAINING 300 TO 400 FT; THE TCASII AURAL MESSAGE CHANGED TO 'MONITOR VERT SPD' AND OUR RATE OF CLB WAS THEREFORE DECREASED. AT THIS TIME LIGHTS OF AN ACFT COULD BE SEEN REFLECTING OFF THE CLOUDS JUST BELOW OUR ACFT (ESTIMATED DISTANCE 1 TO 2 MI). APCH CTL NOW QUESTIONED OUR ALT TO REMIND US THAT WE WERE ASSIGNED 11000 FT. WE ADVISED APCH CTL THAT WE WERE FOLLOWING A TCASII COMMAND TO CLB. CTL STATED THAT THE ACFT WE HAD GONE OVER WAS ASSIGNED TO 10000 FT AND THAT WE DID HAVE TFC AT 12000 FT. BY THIS TIME WE HAD RECEIVED A 'CLR OF CONFLICT' MESSAGE FROM THE TCASII SYS AND HAD BEGUN A RETURN TO 11000 FT (ESTIMATE THAT WE HAD CLBED TO 11700 OR 11800 FT BEFORE A DSCNT COULD BE MADE BACK TO ALT). THE TFC AT 12 O'CLOCK AT 12000 FT WAS IDENTIFIED VISUALLY BY THE CREW (APPROX 5 MI). BY THIS TIME WE WERE LEVELING BACK AT THE ASSIGNED ALT OF 11000 FT. IF THE ACFT BELOW US HAD BEEN CLBING TO 10000 FT; THE TCASII SYS WOULD NOT KNOW THAT IT WAS GOING TO LEVEL AT 10000 FT AND WOULD ISSUE A RA SUCH AS WE RECEIVED. WE DO NOT KNOW IF THIS WAS THE CASE; BUT SEEING THE LIGHTS OF THE OTHER ACFT MADE US BELIEVE THAT THE TCASII SYS SAVED US FROM A NEAR MISS. SUGGEST THAT ALL CTLRS ADVISE CREWS WHEN TFC IF CLBING OR DSNDING TOWARD THEIR ACFT SO THAT BETTER EVALUATIONS CAN BE MADE OF TCASII WARNINGS.