Narrative:

WX at dfw was clear with visibility at 10+ mi. We were vectored for a visual approach to runway 18R downwind; base; final. I was flying the aircraft with autoplt on; and intended to intercept the localizer on autoplt. Approach had us at a 360 degree heading and gave us a turn to 090 degrees and asked if we had the aircraft we were following in sight. We acknowledged we did in fact have the aircraft in sight and he cleared us for a visual approach to ibr. I turned the heading select knob toward netee for the FAF and then selected approach mode and also command 'B' on autoplt. I had also slowed the aircraft to 160 KTS since we had a tailwind on base leg and I wanted to be sure the aircraft would not overshoot final. Aircraft approached localizer course and flew right through localizer. I clicked off the autoplt immediately and began a right turn back toward localizer. As mentioned earlier; we had a tailwind on base and this caused aircraft to fly further off course than if no wind was involved. Aircraft went past highway 182 and approximately 1/2 way into terminal area before heading back toward localizer course. This is when I received a brief TA alert (one traffic announcement and then went away). I was not able to make visual contact with any other aircraft and continued back to localizer course and landed aircraft without further incident. It is also interesting to note that ATC made no comments about the deviation on radio. This event concerns me because hand flying this approach would have been no problem; however; when allowing the technology of the aircraft to do the work; one must be vigilant of procedures and confident the aircraft will do the job properly. The approach was set up properly according to procedures and should have intercepted the localizer. The only reason I could come up with that it didn't intercept the course is the active waypoint changed from legre to netee because dfw turned us between these waypoints and the FMC was not updated to reflect this. When flying approachs at airports with parallel approachs and using the technology of the aircraft; it becomes extremely important to verify your active waypoint prior to intercepting the course.

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Original NASA ASRS Text

Title: B717 AUTOFLT SYS FLIES THROUGH LOC WITHOUT CAPTURE ON RWY 18R AT DFW.

Narrative: WX AT DFW WAS CLR WITH VISIBILITY AT 10+ MI. WE WERE VECTORED FOR A VISUAL APCH TO RWY 18R DOWNWIND; BASE; FINAL. I WAS FLYING THE ACFT WITH AUTOPLT ON; AND INTENDED TO INTERCEPT THE LOC ON AUTOPLT. APCH HAD US AT A 360 DEG HDG AND GAVE US A TURN TO 090 DEGS AND ASKED IF WE HAD THE ACFT WE WERE FOLLOWING IN SIGHT. WE ACKNOWLEDGED WE DID IN FACT HAVE THE ACFT IN SIGHT AND HE CLRED US FOR A VISUAL APCH TO IBR. I TURNED THE HDG SELECT KNOB TOWARD NETEE FOR THE FAF AND THEN SELECTED APCH MODE AND ALSO COMMAND 'B' ON AUTOPLT. I HAD ALSO SLOWED THE ACFT TO 160 KTS SINCE WE HAD A TAILWIND ON BASE LEG AND I WANTED TO BE SURE THE ACFT WOULD NOT OVERSHOOT FINAL. ACFT APCHED LOC COURSE AND FLEW RIGHT THROUGH LOC. I CLICKED OFF THE AUTOPLT IMMEDIATELY AND BEGAN A R TURN BACK TOWARD LOC. AS MENTIONED EARLIER; WE HAD A TAILWIND ON BASE AND THIS CAUSED ACFT TO FLY FURTHER OFF COURSE THAN IF NO WIND WAS INVOLVED. ACFT WENT PAST HWY 182 AND APPROX 1/2 WAY INTO TERMINAL AREA BEFORE HEADING BACK TOWARD LOC COURSE. THIS IS WHEN I RECEIVED A BRIEF TA ALERT (ONE TFC ANNOUNCEMENT AND THEN WENT AWAY). I WAS NOT ABLE TO MAKE VISUAL CONTACT WITH ANY OTHER ACFT AND CONTINUED BACK TO LOC COURSE AND LANDED ACFT WITHOUT FURTHER INCIDENT. IT IS ALSO INTERESTING TO NOTE THAT ATC MADE NO COMMENTS ABOUT THE DEV ON RADIO. THIS EVENT CONCERNS ME BECAUSE HAND FLYING THIS APCH WOULD HAVE BEEN NO PROB; HOWEVER; WHEN ALLOWING THE TECHNOLOGY OF THE ACFT TO DO THE WORK; ONE MUST BE VIGILANT OF PROCS AND CONFIDENT THE ACFT WILL DO THE JOB PROPERLY. THE APCH WAS SET UP PROPERLY ACCORDING TO PROCS AND SHOULD HAVE INTERCEPTED THE LOC. THE ONLY REASON I COULD COME UP WITH THAT IT DIDN'T INTERCEPT THE COURSE IS THE ACTIVE WAYPOINT CHANGED FROM LEGRE TO NETEE BECAUSE DFW TURNED US BTWN THESE WAYPOINTS AND THE FMC WAS NOT UPDATED TO REFLECT THIS. WHEN FLYING APCHS AT ARPTS WITH PARALLEL APCHS AND USING THE TECHNOLOGY OF THE ACFT; IT BECOMES EXTREMELY IMPORTANT TO VERIFY YOUR ACTIVE WAYPOINT PRIOR TO INTERCEPTING THE COURSE.

Data retrieved from NASA's ASRS site as of January 2009 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.