Narrative:

Our flight was approaching atlanta hartsfield international for an ILS 27L approach. As we approached from the south, we were held at 12000/7000' and 320/250 as long as possible. After headings of 360 degree, 300 degree we were cleared to intercept the runway 27L localizer and descend to 2800'. The autoplt was engaged and captured the localizer normally. As we rolled out of our left hand descending turn to intercept, approach control pointed out our preceeding traffic. The traffic and the airport runway were then acquired and we were cleared for a visibility to runway 27L. At this point, the controller told us to turn to a heading of 210 degree immediately. He then pointed out medium large transport traffic to our right and high. Immediately prior to this our extra crew member had sighted the traffic and annunciated his visibility so the turn to 210 degree was expeditious. The medium large transport appeared to have overshot his localizer on the north complex. Once visibility was established, sep was maintained and a normal approach and landing accomplished. Two things that might have contributed to this situation were: keeping us high during the approach. Had we been at 2800' vertical sep would probably be adequate. Both aircraft seemed to have approach their locs at opp head on angles. We have no way of knowing if or why the other aircraft overshot. Supplemental information from acn 146785. It would reduce the chance of a conflict, in low ceiling and low visibility conditions, if a staggered turn on were used for simultaneous approach arrs, as is required for parallel approach operations.

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Original NASA ASRS Text

Title: ACFT OVERSHOT FINAL APCH AND CAME IN CLOSE PROX TO ANOTHER ACFT ON THE PARALLEL APCH.

Narrative: OUR FLT WAS APCHING ATLANTA HARTSFIELD INTL FOR AN ILS 27L APCH. AS WE APCHED FROM THE S, WE WERE HELD AT 12000/7000' AND 320/250 AS LONG AS POSSIBLE. AFTER HDGS OF 360 DEG, 300 DEG WE WERE CLRED TO INTERCEPT THE RWY 27L LOC AND DSND TO 2800'. THE AUTOPLT WAS ENGAGED AND CAPTURED THE LOC NORMALLY. AS WE ROLLED OUT OF OUR L HAND DSNDING TURN TO INTERCEPT, APCH CTL POINTED OUT OUR PRECEEDING TFC. THE TFC AND THE ARPT RWY WERE THEN ACQUIRED AND WE WERE CLRED FOR A VIS TO RWY 27L. AT THIS POINT, THE CTLR TOLD US TO TURN TO A HDG OF 210 DEG IMMEDIATELY. HE THEN POINTED OUT MLG TFC TO OUR R AND HIGH. IMMEDIATELY PRIOR TO THIS OUR EXTRA CREW MEMBER HAD SIGHTED THE TFC AND ANNUNCIATED HIS VIS SO THE TURN TO 210 DEG WAS EXPEDITIOUS. THE MLG APPEARED TO HAVE OVERSHOT HIS LOC ON THE N COMPLEX. ONCE VIS WAS ESTABLISHED, SEP WAS MAINTAINED AND A NORMAL APCH AND LNDG ACCOMPLISHED. TWO THINGS THAT MIGHT HAVE CONTRIBUTED TO THIS SITUATION WERE: KEEPING US HIGH DURING THE APCH. HAD WE BEEN AT 2800' VERT SEP WOULD PROBABLY BE ADEQUATE. BOTH ACFT SEEMED TO HAVE APCH THEIR LOCS AT OPP HEAD ON ANGLES. WE HAVE NO WAY OF KNOWING IF OR WHY THE OTHER ACFT OVERSHOT. SUPPLEMENTAL INFO FROM ACN 146785. IT WOULD REDUCE THE CHANCE OF A CONFLICT, IN LOW CEILING AND LOW VISIBILITY CONDITIONS, IF A STAGGERED TURN ON WERE USED FOR SIMULTANEOUS APCH ARRS, AS IS REQUIRED FOR PARALLEL APCH OPS.

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.