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.