ACR X EXECUTED A GAR BECAUSE OF SUSPECTED TFC ON FINAL APCH TO SAME RWY.

Narrative

ACR X CLRED FOR VISUAL APCH RWY 1R AT IAD; R TFC AS PER NORMAL OPS. INFORMED BY RADAR OF TFC LNDG PARALLEL RWY IL AND SWITCHED TO TWR. FO AND I IDENTED WHAT WE THOUGHT WAS TFC LINED UP ON RWY 1L. OVER TO TWR; CLRED TO LAND RWY 1R. EVERYTHING NORMAL AS WE TURN R BASE. TURNING FINAL MY FO ALERTS ME TO TFC OUT THE L SIDE WINDOW (MY APPROX 8:30 POS). PREVIOUS TO THIS FINAL HAD APPEARED CLR SO I WAS VERY SURPRISED TO LOOK L AND SEE TFC MY FO HAD INDICATED; VERY CLOSE; NOW MOVING TO MY 7:30 POS (WE'RE IN TURN); AND LINED UP ON RWY 1R (OUR RWY). I ESTIMATE THIS TFC TO HAVE BEEN APPROX 100 FT BELOW US AND APPROX 1000 FT BEHIND; TRACKING THE RWY 1R FINAL COURSE WHICH WE ARE IN THE PROCESS OF LINING UP ON. IMMEDIATELY INITIATE GAR AND EVASIVE MANEUVER (CLBING R TURN AWAY FROM TFC CONFLICT). GIVE TWR THE GAR CALL -- THEY DON'T ASK REASON FOR GAR. ASK TWR FOR INSTRUCTIONS; AND ISSUED RWY HDG; MAINTAIN 2000 FT. INFORM TWR THAT WE WENT AROUND FOR TFC CONFLICT. TWR SAYS THEY HAVE NO CONFLICTING TFC; AND THAT THE ONLY POSSIBLE TFC WE MIGHT HAVE BEEN REACTING TO WAS A 757 WHICH HAD BEEN WELL ESTABLISHED ON RWY 1L; AND HAD LANDED NORMALLY ON RWY 1L. THIS IS VERY INTERESTING GIVEN THAT THE TFC WHICH HAD COME IN CONFLICT WITH US WAS STILL IN MY CLR VIEW; AND AS THE TWR IS MAKING THIS LAST XMISSION; I AM LOOKING RIGHT AT THE CONFLICTING TFC WHICH IS VERY MUCH AIRBORNE; TRACKING THE RWY 1R CTRLINE NBOUND; RIGHT AT ABOUT THE RWY MIDPOINT AND APPROX 1000-1500 FT AGL OUR POS IS OFFSET APPROX 1/2 MI E OF CTRLINE; 2000 FT MSL. IN EFFECT WE ARE 'FORMATION FLYING' (CONFLICT TFC AT OUR 8 O'CLOCK AND 1/2 MI; 500 FT BELOW) WITH TFC THE TWR DOESN'T SEE AND SAYS ISN'T THERE. I TAKE OVER RADIO AND INFORM TWR THAT I'M LOOKING RIGHT AT THIS GUY. RESPONSE IS TWR STATES HE 'WISHES HE KNEW WHAT WE WERE LOOKING AT'; TURNED OVER TO RADAR AGAIN AND ISSUED A R TURN TO 130 DEGS; WHICH CAUSES US TO LOSE SIGHT OF CONFLICT TFC; AND SUBSEQUENTLY WE DO NOT RE-ACQUIRE. COME BACK AROUND R DOWNWIND AND LAND WITHOUT FURTHER BIZARRE INCIDENT. AFTER LNDG GO IN TO CALL TWR ON PHONE. TWR CONTINUES TO MAINTAIN THAT THERE WAS NO SUCH TFC. AS I HANG UP PHONE; I AM APCHED BY 1 OF OUR DASH-8 CAPTS; WHO WAS ON R DOWNWIND TO RWY 1R DURING OUR CONFLICT; GAR. THIS CAPT TELLS ME THAT FROM HIS VANTAGE POINT ABOUT 1 1/2 MI TO THE E HE OBSERVED THE ENTIRE SEQUENCE OF EVENTS; AND THAT HE AND HIS FO BOTH CLRLY SAW THE CONFLICT TFC. HE TOLD ME THAT HE ALSO INFORMED THE TWR ON THE RADIO THAT HE HAD CLRLY SEEN THIS 'PHANTOM' TFC; AND THAT TWR HAD JUST SAID 'NO SUCH TFC.' 4 PLTS IN 2 AIRPLANES DISAGREE.