Narrative:

Air carrier X cleared for visual approach runway 1R at iad, right traffic as per normal operations. Informed by radar of traffic landing parallel runway il and switched to tower. First officer and I idented what we thought was traffic lined up on runway 1L. Over to tower, cleared to land runway 1R. Everything normal as we turn right base. Turning final my first officer alerts me to traffic out the left side window (my approximately 8:30 position). Previous to this final had appeared clear so I was very surprised to look left and see traffic my first officer had indicated, very close, now moving to my 7:30 position (we're in turn), and lined up on runway 1R (our runway). I estimate this traffic to have been approximately 100 ft below us and approximately 1000 ft behind, tracking the runway 1R final course which we are in the process of lining up on. Immediately initiate go around and evasive maneuver (climbing right turn away from traffic conflict). Give tower the go around call -- they don't ask reason for go around. Ask tower for instructions, and issued runway heading, maintain 2000 ft. Inform tower that we went around for traffic conflict. Tower says they have no conflicting traffic, and that the only possible traffic we might have been reacting to was a 757 which had been well established on runway 1L, and had landed normally on runway 1L. This is very interesting given that the traffic which had come in conflict with us was still in my clear view, and as the tower is making this last transmission, I am looking right at the conflicting traffic which is very much airborne, tracking the runway 1R centerline northbound, right at about the runway midpoint and approximately 1000-1500 ft AGL our position is offset approximately 1/2 mi east of centerline, 2000 ft MSL. In effect we are 'formation flying' (conflict traffic at our 8 O'clock and 1/2 mi, 500 ft below) with traffic the tower doesn't see and says isn't there. I take over radio and inform tower that I'm looking right at this guy. Response is tower states he 'wishes he knew what we were looking at', turned over to radar again and issued a right turn to 130 degrees, which causes us to lose sight of conflict traffic, and subsequently we do not re-acquire. Come back around right downwind and land without further bizarre incident. After landing go in to call tower on phone. Tower continues to maintain that there was no such traffic. As I hang up phone, I am approached by 1 of our dash-8 capts, who was on right downwind to runway 1R during our conflict, go around. This captain tells me that from his vantage point about 1 1/2 mi to the east he observed the entire sequence of events, and that he and his first officer both clearly saw the conflict traffic. He told me that he also informed the tower on the radio that he had clearly seen this 'phantom' traffic, and that tower had just said 'no such traffic.' 4 pilots in 2 airplanes disagree.

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Original NASA ASRS Text

Title: 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.

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.