Narrative:

During descent prior to handoff to lax tower, we were given 2 airspeed changes which affected our ability to meet altitude constraints on the approach. Sometime during the time it took to reprogram the FMS, the localizer track mode reverted to 'heading hold.' neither of us noticed this until approach control advised that we were drifting off course to the north of the runway 25L localizer. We made an immediate correction, and I am almost positive that no traffic conflict occurred. Neither of us knows how the localizer track mode was dropped, but we missed it because we were fixated on the vertical constraint change.

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Original NASA ASRS Text

Title: AN ACR A300 FLC HAD THE AUTOFLT SYS CHANGE MODES FROM LOC TRACK TO HDG HOLD AND THEY GOT OFF COURSE WHILE THEY WERE 'HEAD DOWN' ENTERING DATA INTO THE FMS.

Narrative: DURING DSCNT PRIOR TO HDOF TO LAX TWR, WE WERE GIVEN 2 AIRSPD CHANGES WHICH AFFECTED OUR ABILITY TO MEET ALT CONSTRAINTS ON THE APCH. SOMETIME DURING THE TIME IT TOOK TO REPROGRAM THE FMS, THE LOC TRACK MODE REVERTED TO 'HDG HOLD.' NEITHER OF US NOTICED THIS UNTIL APCH CTL ADVISED THAT WE WERE DRIFTING OFF COURSE TO THE N OF THE RWY 25L LOC. WE MADE AN IMMEDIATE CORRECTION, AND I AM ALMOST POSITIVE THAT NO TFC CONFLICT OCCURRED. NEITHER OF US KNOWS HOW THE LOC TRACK MODE WAS DROPPED, BUT WE MISSED IT BECAUSE WE WERE FIXATED ON THE VERT CONSTRAINT CHANGE.

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.