Narrative:

We had briefed both runway 25L or 24R @ lax. Right at civet; on initial fix from which traffic is split for these runways; we were assigned runway 24R and given a speed reduction. When the right runway was selected; the FMS went through its checks and the plane went into heading hold rather than navigation and this was missed as we slowed the plane. We noticed we were off course and corrected back. It would be helpful to pilots in busy airspace to be told of runway assignments prior to initial fixes in order to provide sufficient time for crews to get the FMS updated.

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Original NASA ASRS Text

Title: TRACK DEV TAKES PLACE WHEN MD90 FLT CREW IS GIVEN RWY CHANGE AT CIVET ON THE CIVET STAR TO LAX.

Narrative: WE HAD BRIEFED BOTH RWY 25L OR 24R @ LAX. R AT CIVET; ON INITIAL FIX FROM WHICH TFC IS SPLIT FOR THESE RWYS; WE WERE ASSIGNED RWY 24R AND GIVEN A SPD REDUCTION. WHEN THE R RWY WAS SELECTED; THE FMS WENT THROUGH ITS CHKS AND THE PLANE WENT INTO HDG HOLD RATHER THAN NAV AND THIS WAS MISSED AS WE SLOWED THE PLANE. WE NOTICED WE WERE OFF COURSE AND CORRECTED BACK. IT WOULD BE HELPFUL TO PLTS IN BUSY AIRSPACE TO BE TOLD OF RWY ASSIGNMENTS PRIOR TO INITIAL FIXES IN ORDER TO PROVIDE SUFFICIENT TIME FOR CREWS TO GET THE FMS UPDATED.

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.