Narrative:

While on a radar vector downwind for 33L visual at kbwi, target was visually acquired at 12 O'clock slightly low and approximately 5-10 NM range. It was noted on TCASII screen as coming toward us and approximately 500 ft lower. At approximately 4- 5 NM, we received TCASII TA on that traffic. When traffic was approximately 10 O'clock and approximately 1 NM we received TCASII RA which directed a climb. I climbed aircraft to 4300 ft MSL to satisfy TCASII RA requirement. At same time that TCASII RA was in progress, approach control advised us of traffic. We advised approach of +300 ft altitude deviation for TCASII RA and that we were visual on traffic. It was very busy on approach control, multi- target environment, people stepping on each other on frequency, similar sounding call signs. It was also night VMC and difficult to estimate ranges of traffic. Approach controller was very good. I could tell he was experienced, but he may have just simply been overwhelmed by amount of traffic. It was one of the busiest ATC environments I've ever seen. Almost mayhem!

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Original NASA ASRS Text

Title: CAPT OF ACR MLG ACFT DEVIATED FROM ASSIGNED ALT UPON SIGHTING, TOGETHER WITH A TCASII ALERT, OF ANOTHER ACFT COMING 'HEAD ON' AT A LOWER ALT.

Narrative: WHILE ON A RADAR VECTOR DOWNWIND FOR 33L VISUAL AT KBWI, TARGET WAS VISUALLY ACQUIRED AT 12 O'CLOCK SLIGHTLY LOW AND APPROX 5-10 NM RANGE. IT WAS NOTED ON TCASII SCREEN AS COMING TOWARD US AND APPROX 500 FT LOWER. AT APPROX 4- 5 NM, WE RECEIVED TCASII TA ON THAT TFC. WHEN TFC WAS APPROX 10 O'CLOCK AND APPROX 1 NM WE RECEIVED TCASII RA WHICH DIRECTED A CLB. I CLBED ACFT TO 4300 FT MSL TO SATISFY TCASII RA REQUIREMENT. AT SAME TIME THAT TCASII RA WAS IN PROGRESS, APCH CTL ADVISED US OF TFC. WE ADVISED APCH OF +300 FT ALT DEV FOR TCASII RA AND THAT WE WERE VISUAL ON TFC. IT WAS VERY BUSY ON APCH CTL, MULTI- TARGET ENVIRONMENT, PEOPLE STEPPING ON EACH OTHER ON FREQ, SIMILAR SOUNDING CALL SIGNS. IT WAS ALSO NIGHT VMC AND DIFFICULT TO ESTIMATE RANGES OF TFC. APCH CTLR WAS VERY GOOD. I COULD TELL HE WAS EXPERIENCED, BUT HE MAY HAVE JUST SIMPLY BEEN OVERWHELMED BY AMOUNT OF TFC. IT WAS ONE OF THE BUSIEST ATC ENVIRONMENTS I'VE EVER SEEN. ALMOST MAYHEM!

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.