Narrative:

I was on downwind for a visual approach to runway 1L at dulles. I was on a heading of 190 degrees at 4000 ft and 190 KIAS. At approximately 12-14 mi south of dulles (just south of manassas airport) approach control turned me to a heading of 060 degrees. Just about the time I rolled out on this heading traffic was picked up by TCASII at 1-2 O'clock and 5 mi. The traffic was 200 ft above me on the screen and closing. Shortly thereafter, I received a TA on the traffic which was still closing. I then received an RA on the traffic in question which was now 100 ft above me on the screen. The TCASII initially called for a climb but almost immediately reversed itself and called for a descent at a rate of 2500 FPM. The traffic at the time appeared to be about 1 - 1 1/2 mi away from us. The radio frequency was extremely congested and we had received no information on the traffic from approach control. I immediately rolled the aircraft into a left hand bank and closed the throttles to idle in order to take evasive action. Some time shortly thereafter, while I was in the turn, dulles approach control advised us to turn left immediately for mdt traffic at 1-2 O'clock. I was already in the turn. I rolled out on a heading of 020 degrees and leveled off at 3300 ft. We then called dulles 3 times but got no response. Again, the frequencys were extremely congested. Shortly thereafter, we received a handoff from approach control to tower and landed uneventfully. During this incident I never did see the traffic visually. I only saw it on the TCASII screen. While I was taking evasive action my copilot did see the traffic visually and advised me that the traffic appeared to be taking evasive action to the left.

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Original NASA ASRS Text

Title: MLG GETS TCASII RA AND TURNS.

Narrative: I WAS ON DOWNWIND FOR A VISUAL APCH TO RWY 1L AT DULLES. I WAS ON A HDG OF 190 DEGS AT 4000 FT AND 190 KIAS. AT APPROX 12-14 MI S OF DULLES (JUST S OF MANASSAS ARPT) APCH CTL TURNED ME TO A HDG OF 060 DEGS. JUST ABOUT THE TIME I ROLLED OUT ON THIS HDG TFC WAS PICKED UP BY TCASII AT 1-2 O'CLOCK AND 5 MI. THE TFC WAS 200 FT ABOVE ME ON THE SCREEN AND CLOSING. SHORTLY THEREAFTER, I RECEIVED A TA ON THE TFC WHICH WAS STILL CLOSING. I THEN RECEIVED AN RA ON THE TFC IN QUESTION WHICH WAS NOW 100 FT ABOVE ME ON THE SCREEN. THE TCASII INITIALLY CALLED FOR A CLB BUT ALMOST IMMEDIATELY REVERSED ITSELF AND CALLED FOR A DSCNT AT A RATE OF 2500 FPM. THE TFC AT THE TIME APPEARED TO BE ABOUT 1 - 1 1/2 MI AWAY FROM US. THE RADIO FREQ WAS EXTREMELY CONGESTED AND WE HAD RECEIVED NO INFO ON THE TFC FROM APCH CTL. I IMMEDIATELY ROLLED THE ACFT INTO A L HAND BANK AND CLOSED THE THROTTLES TO IDLE IN ORDER TO TAKE EVASIVE ACTION. SOME TIME SHORTLY THEREAFTER, WHILE I WAS IN THE TURN, DULLES APCH CTL ADVISED US TO TURN L IMMEDIATELY FOR MDT TFC AT 1-2 O'CLOCK. I WAS ALREADY IN THE TURN. I ROLLED OUT ON A HDG OF 020 DEGS AND LEVELED OFF AT 3300 FT. WE THEN CALLED DULLES 3 TIMES BUT GOT NO RESPONSE. AGAIN, THE FREQS WERE EXTREMELY CONGESTED. SHORTLY THEREAFTER, WE RECEIVED A HDOF FROM APCH CTL TO TWR AND LANDED UNEVENTFULLY. DURING THIS INCIDENT I NEVER DID SEE THE TFC VISUALLY. I ONLY SAW IT ON THE TCASII SCREEN. WHILE I WAS TAKING EVASIVE ACTION MY COPLT DID SEE THE TFC VISUALLY AND ADVISED ME THAT THE TFC APPEARED TO BE TAKING EVASIVE ACTION TO THE L.

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.