Narrative:

We had arrived in the atl area and were being vectored for our approach, approach control advised us of traffic at 12 O'clock and we informed him that we were IFR. Without giving any kind of traffic alert the TCASII system issued a RA with the aural message to 'climb, climb, climb'. In accordance with the operating procedure for our aircraft, the autoplt was disconnected and a climb initiated from the assigned altitude of 11000 ft. After gaining 300 to 400 ft, the TCASII aural message changed to 'monitor vertical speed' and our rate of climb was therefore decreased. At this time lights of an aircraft could be seen reflecting off the clouds just below our aircraft (estimated distance 1 to 2 mi). Approach control now questioned our altitude to remind us that we were assigned 11000 ft. We advised approach control that we were following a TCASII command to climb. Control stated that the aircraft we had gone over was assigned to 10000 ft and that we did have traffic at 12000 ft. By this time we had received a 'clear of conflict' message from the TCASII system and had begun a return to 11000 ft (estimate that we had climbed to 11700 or 11800 ft before a descent could be made back to altitude). The traffic at 12 O'clock at 12000 ft was identified visually by the crew (approximately 5 mi). By this time we were leveling back at the assigned altitude of 11000 ft. If the aircraft below us had been climbing to 10000 ft, the TCASII system 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 aircraft made us believe that the TCASII system saved us from a near miss. Suggest that all controllers advise crews when traffic if climbing or descending toward their aircraft so that better evaluations can be made of TCASII warnings.

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Original NASA ASRS Text

Title: 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.

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.