Narrative:

Flight was proceeding under stl radar approach control. WX was VMC. We were established on runway 30R localizer at 5000 ft. We then received a clearance to descend to 3500 ft. As the aircraft descended through approximately 4000 ft, we received a TCASII RA to 'climb.' while executing the escape maneuver we noticed a red symbol directly under the aircraft symbol on the ivsi with a separation notation of '00' ft. Shortly after initiating our climb, the captain observed an light transport Y slowly diverging from the left side of our aircraft and directly abeam, but now below us. At about the same time, we received a 'clear of conflict' advisory. We immediately advised the controller we had received an RA and had complied with TCASII commands to climb. The controller then advised us we had light transport Y traffic off our left on visual approach to runway 30L and then cleared us for visual approach to runway 30R. The remainder of the approach and landing was uneventful. After landing the captain contacted a supervisor at stl TRACON and was advised that, at the time of the incident in question, the light transport Y had been proceeding on a visual approach clearance to runway 30L. He further stated that this aircraft had reported us in sight and had been instructed to maintain visual separation. Prior to joining the localizer, we were issued no TA regarding the light transport Y even though we were still under radar control. Also, the ATIS advertised visual approachs to runway 30L and runway 30R utilizing runway 30R ILS and runway 30L lda-DME. Why did the light transport Y fly to the right of his visual approach course? Realistically, we cannot be presumed responsible for visual separation from traffic we were unable to see and that which was not reported to us by ATC.

Related reports:

Google
 

Original NASA ASRS Text

Title: LGT ON VECTOR FOR VISUAL APCH RECEIVED A TCASII RA ON AN LTT ON VISUAL APCH TO PARALLEL RWY. LTT WENT VISUALLY BELOW LGT IN CLOSE PROX.

Narrative: FLT WAS PROCEEDING UNDER STL RADAR APCH CTL. WX WAS VMC. WE WERE ESTABLISHED ON RWY 30R LOC AT 5000 FT. WE THEN RECEIVED A CLRNC TO DSND TO 3500 FT. AS THE ACFT DSNDED THROUGH APPROX 4000 FT, WE RECEIVED A TCASII RA TO 'CLB.' WHILE EXECUTING THE ESCAPE MANEUVER WE NOTICED A RED SYMBOL DIRECTLY UNDER THE ACFT SYMBOL ON THE IVSI WITH A SEPARATION NOTATION OF '00' FT. SHORTLY AFTER INITIATING OUR CLB, THE CAPT OBSERVED AN LTT Y SLOWLY DIVERGING FROM THE L SIDE OF OUR ACFT AND DIRECTLY ABEAM, BUT NOW BELOW US. AT ABOUT THE SAME TIME, WE RECEIVED A 'CLR OF CONFLICT' ADVISORY. WE IMMEDIATELY ADVISED THE CTLR WE HAD RECEIVED AN RA AND HAD COMPLIED WITH TCASII COMMANDS TO CLB. THE CTLR THEN ADVISED US WE HAD LTT Y TFC OFF OUR L ON VISUAL APCH TO RWY 30L AND THEN CLRED US FOR VISUAL APCH TO RWY 30R. THE REMAINDER OF THE APCH AND LNDG WAS UNEVENTFUL. AFTER LNDG THE CAPT CONTACTED A SUPVR AT STL TRACON AND WAS ADVISED THAT, AT THE TIME OF THE INCIDENT IN QUESTION, THE LTT Y HAD BEEN PROCEEDING ON A VISUAL APCH CLRNC TO RWY 30L. HE FURTHER STATED THAT THIS ACFT HAD RPTED US IN SIGHT AND HAD BEEN INSTRUCTED TO MAINTAIN VISUAL SEPARATION. PRIOR TO JOINING THE LOC, WE WERE ISSUED NO TA REGARDING THE LTT Y EVEN THOUGH WE WERE STILL UNDER RADAR CTL. ALSO, THE ATIS ADVERTISED VISUAL APCHS TO RWY 30L AND RWY 30R UTILIZING RWY 30R ILS AND RWY 30L LDA-DME. WHY DID THE LTT Y FLY TO THE R OF HIS VISUAL APCH COURSE? REALISTICALLY, WE CANNOT BE PRESUMED RESPONSIBLE FOR VISUAL SEPARATION FROM TFC WE WERE UNABLE TO SEE AND THAT WHICH WAS NOT RPTED TO US BY ATC.

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.