Narrative:

During approach, in WX, ATC changed the approach from an ILS 36L to ILS 35R just prior to our turning base leg. I quickly briefed the new approach, but failed to insure the new ILS frequency was tuned and identified. Approach gave us a turn to intercept final. The copilot (flying) and I thought we had overshot the localizer to 35R and were beginning to turn to 35R localizer when approach gave us a heading to 030 to intercept the 35R localizer. The approach was completed with no apparent conflict. This incident occurred after a 12 hour day, beginning with an early am sign-in and the WX had been bad. While these events may have been factors, we should have been alert to the situation being ripe for a mistake. Supplemental information from acn 138229: I started a gradual turn to fly back toward the course and stated that we were going to really overshoot. At this time, the captain exclaimed that we had never changed the ILS frequency from 36L to 35R. I immediately started a turn back to the original intercept heading. During this time, approach control came back to reconfirm the heading for 35R.

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Original NASA ASRS Text

Title: ACR MLG SWITCHED TO ILS ON 35R FROM 36L AT DFW FORGETS TO CHANGE ILS FREQ, BEGINS TO CHASE WRONG LOCALIZER.

Narrative: DURING APCH, IN WX, ATC CHANGED THE APCH FROM AN ILS 36L TO ILS 35R JUST PRIOR TO OUR TURNING BASE LEG. I QUICKLY BRIEFED THE NEW APCH, BUT FAILED TO INSURE THE NEW ILS FREQ WAS TUNED AND IDENTIFIED. APCH GAVE US A TURN TO INTERCEPT FINAL. THE COPLT (FLYING) AND I THOUGHT WE HAD OVERSHOT THE LOC TO 35R AND WERE BEGINNING TO TURN TO 35R LOC WHEN APCH GAVE US A HDG TO 030 TO INTERCEPT THE 35R LOC. THE APCH WAS COMPLETED WITH NO APPARENT CONFLICT. THIS INCIDENT OCCURRED AFTER A 12 HR DAY, BEGINNING WITH AN EARLY AM SIGN-IN AND THE WX HAD BEEN BAD. WHILE THESE EVENTS MAY HAVE BEEN FACTORS, WE SHOULD HAVE BEEN ALERT TO THE SITUATION BEING RIPE FOR A MISTAKE. SUPPLEMENTAL INFORMATION FROM ACN 138229: I STARTED A GRADUAL TURN TO FLY BACK TOWARD THE COURSE AND STATED THAT WE WERE GOING TO REALLY OVERSHOOT. AT THIS TIME, THE CAPT EXCLAIMED THAT WE HAD NEVER CHANGED THE ILS FREQ FROM 36L TO 35R. I IMMEDIATELY STARTED A TURN BACK TO THE ORIGINAL INTERCEPT HDG. DURING THIS TIME, APCH CTL CAME BACK TO RECONFIRM THE HDG FOR 35R.

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.