Narrative:

The captain was flying a vector on the downwind for approach to runway 21 at chs. ATC had cleared us to descend to 8;000 ft and called out traffic '10 o'clock; 3 miles; altitude indicates 7;300 ft. Leaving approximately 8;500 ft; we received a traffic alert; followed less than two seconds later by a 'climb; climb. The captain disengaged the autopilot and immediately added power and started to climb. We were both on 20-mile scale since we were on a wide downwind; but when I looked at the vsi; I also noted that we were at approximately 8;100 ft with 300 ft of separation from the traffic that appeared to be right under our nose (according to the radar). We were never able to pick up the traffic visually because there was a broken layer from approximately 6;000 ft to 8;000 ft. I monitored the vertical speed and our separation and saw that we never approached the traffic closer than 300 ft. The best I can figure; based on our indications; the uncontrolled traffic must have climbed to at least 7;800 ft and was unaware of our presence. I told charleston approach about the RA and he responded; 'okay; traffic is behind you; no factor.'ATC put us into a situation by vectoring us on a downwind with traffic near our altitude. They were obviously not talking to this other traffic; because there is no way they would have put us that close. This situation was made worse by the fact that the uncontrolled traffic was flying in and around a thick broken layer of clouds which prevented us from ever gaining visual contact. Charleston approach needs to know that this is too close for two airplanes that are not both under their control.

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Original NASA ASRS Text

Title: B737 flight crew experienced a TCAS RA during descent into CHS. Crew had been advised of the VFR traffic by Approach Control.

Narrative: The Captain was flying a vector on the downwind for approach to Runway 21 at CHS. ATC had cleared us to descend to 8;000 FT and called out traffic '10 o'clock; 3 miles; altitude indicates 7;300 FT. Leaving approximately 8;500 FT; we received a Traffic Alert; followed less than two seconds later by a 'Climb; Climb. The Captain disengaged the autopilot and immediately added power and started to climb. We were both on 20-mile scale since we were on a wide downwind; but when I looked at the VSI; I also noted that we were at approximately 8;100 FT with 300 FT of separation from the traffic that appeared to be right under our nose (according to the radar). We were never able to pick up the traffic visually because there was a broken layer from approximately 6;000 FT to 8;000 FT. I monitored the Vertical Speed and our separation and saw that we never approached the traffic closer than 300 FT. The best I can figure; based on our indications; the uncontrolled traffic must have climbed to at least 7;800 FT and was unaware of our presence. I told Charleston Approach about the RA and he responded; 'Okay; traffic is behind you; no factor.'ATC put us into a situation by vectoring us on a downwind with traffic near our altitude. They were obviously not talking to this other traffic; because there is no way they would have put us that close. This situation was made worse by the fact that the uncontrolled traffic was flying in and around a thick broken layer of clouds which prevented us from ever gaining visual contact. Charleston Approach needs to know that this is too close for two airplanes that are not both under their control.

Data retrieved from NASA's ASRS site as of April 2012 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.