Narrative:

Vectored by iad approach to visibility approach to 01R. Called airport in sight and so cleared at about 8-10 mi. Approach then talked to air carrier large transport pointing us out as traffic. Large transport was coming in from east (our 3'clock). He said he had use in sight with small one in front of us. Since I saw no small traffic in front of us, I got suspicious and kept eye on him. He turned in toward runway on collision course with us and when he continued turning in broke left toward oil where fortunately no one was on final. Called and told approach of our action and at about this time large transport broke sharply to his left as he apparently now had the proper picture. We were reclred visibility to 01R and did so with large transport now behind us. Never told to switch to tower so did so on our own and cleared to land on 01R. This ia another classic example of visually following traffic that has not been positively idented. We all do it all the time to expedite traffic flow. Sometimes it bites back and by the regulations we get hung. Problem is too much air traffic. Solution is cut back on air traffic to a safe level.

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Original NASA ASRS Text

Title: ACR ON VISUAL APCH HAS LGT ALSO ON VISUAL BUT SUPPOSEDLY FOLLOWING, TURN TOWARD HIM ON COLLISION COURSE.

Narrative: VECTORED BY IAD APCH TO VIS APCH TO 01R. CALLED ARPT IN SIGHT AND SO CLRED AT ABOUT 8-10 MI. APCH THEN TALKED TO ACR LGT POINTING US OUT AS TFC. LGT WAS COMING IN FROM E (OUR 3'CLOCK). HE SAID HE HAD USE IN SIGHT WITH SMALL ONE IN FRONT OF US. SINCE I SAW NO SMALL TFC IN FRONT OF US, I GOT SUSPICIOUS AND KEPT EYE ON HIM. HE TURNED IN TOWARD RWY ON COLLISION COURSE WITH US AND WHEN HE CONTINUED TURNING IN BROKE LEFT TOWARD OIL WHERE FORTUNATELY NO ONE WAS ON FINAL. CALLED AND TOLD APCH OF OUR ACTION AND AT ABOUT THIS TIME LGT BROKE SHARPLY TO HIS LEFT AS HE APPARENTLY NOW HAD THE PROPER PICTURE. WE WERE RECLRED VIS TO 01R AND DID SO WITH LGT NOW BEHIND US. NEVER TOLD TO SWITCH TO TWR SO DID SO ON OUR OWN AND CLRED TO LAND ON 01R. THIS IA ANOTHER CLASSIC EXAMPLE OF VISUALLY FOLLOWING TFC THAT HAS NOT BEEN POSITIVELY IDENTED. WE ALL DO IT ALL THE TIME TO EXPEDITE TFC FLOW. SOMETIMES IT BITES BACK AND BY THE REGS WE GET HUNG. PROB IS TOO MUCH AIR TFC. SOLUTION IS CUT BACK ON AIR TFC TO A SAFE LEVEL.

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.