Narrative:

First officer was PF. Receiving vectors from atl approach control for approach to runway 26R atl. Assigned heading 180 degrees, followed by right turn to 260 degrees and intercept runway 27R localizer. Traffic issued as B757 at our altitude to follow to runway 26R and B757 1000 ft lower and turning back to intercept runway 27L final, after having flown through final approach course to runway 27L. I reported both aircraft in sight. We were subsequently cleared for the visual approach. While in the banking turn to 260 degrees, we received TCASII TA, showing another aircraft at our altitude, apparently coming from the south for runway 27L. We continued the turn and I established visual contact with the intruder, another CR2. TCASII advanced to RA, with descend instruction. First officer initiated descent. Since I had the aircraft in sight and perceived no direct conflict, I directed first officer to reduce descent and continue turn for runway 26R intercept. Intruder cleared well to our left. I advised approach controller of our altitude deviation resulting from the TCASII RA. We continued uneventfully for landing. Subsequent conversations in air carrier crew room revealed that the intruder was an air carrier CR2 which had not been instructed by ATC to turn wbound to intercept runway 27L final. That aircraft was the second one in a row that ATC had allowed to fly past the final approach course for runway 27L.

Related reports:

Google
 

Original NASA ASRS Text

Title: CL65 FLC DSND DURING TURN TO FINAL IN RESPONSE TO A TCASII RA CAUSED BY ANOTHER CL65 OF THEIR COMPANY WHO HAD OVERSHOT FINAL COURSE FOR AN ADJACENT PARALLEL RWY AND WAS TURNING BACK TO THAT RWY.

Narrative: FO WAS PF. RECEIVING VECTORS FROM ATL APCH CTL FOR APCH TO RWY 26R ATL. ASSIGNED HDG 180 DEGS, FOLLOWED BY R TURN TO 260 DEGS AND INTERCEPT RWY 27R LOC. TFC ISSUED AS B757 AT OUR ALT TO FOLLOW TO RWY 26R AND B757 1000 FT LOWER AND TURNING BACK TO INTERCEPT RWY 27L FINAL, AFTER HAVING FLOWN THROUGH FINAL APCH COURSE TO RWY 27L. I RPTED BOTH ACFT IN SIGHT. WE WERE SUBSEQUENTLY CLRED FOR THE VISUAL APCH. WHILE IN THE BANKING TURN TO 260 DEGS, WE RECEIVED TCASII TA, SHOWING ANOTHER ACFT AT OUR ALT, APPARENTLY COMING FROM THE S FOR RWY 27L. WE CONTINUED THE TURN AND I ESTABLISHED VISUAL CONTACT WITH THE INTRUDER, ANOTHER CR2. TCASII ADVANCED TO RA, WITH DSND INSTRUCTION. FO INITIATED DSCNT. SINCE I HAD THE ACFT IN SIGHT AND PERCEIVED NO DIRECT CONFLICT, I DIRECTED FO TO REDUCE DSCNT AND CONTINUE TURN FOR RWY 26R INTERCEPT. INTRUDER CLRED WELL TO OUR L. I ADVISED APCH CTLR OF OUR ALTDEV RESULTING FROM THE TCASII RA. WE CONTINUED UNEVENTFULLY FOR LNDG. SUBSEQUENT CONVERSATIONS IN ACR CREW ROOM REVEALED THAT THE INTRUDER WAS AN ACR CR2 WHICH HAD NOT BEEN INSTRUCTED BY ATC TO TURN WBOUND TO INTERCEPT RWY 27L FINAL. THAT ACFT WAS THE SECOND ONE IN A ROW THAT ATC HAD ALLOWED TO FLY PAST THE FINAL APCH COURSE FOR RWY 27L.

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.