Narrative:

While on approach to lax on the SEAVU1 expecting the ILS runway 25R; approach changed our runway to runway 24R. The FMC became very difficult to update with extended periods of a blank FMC or a 'standby one' message displayed. Some waypoints of the new arrival were missing and had to be input manually. Once established on the new arrival the FMC showed the aircraft in LNAV but north of course and not correcting. Manual corrections were applied to an uneventful approach and landing. No deviations were noted by ATC.

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Original NASA ASRS Text

Title: A B757 ON THE SEAVU ARR TO LAX EXPERIENCED FMC DIFFICULTIES THAT RESULTED IN TRACK DEVS.

Narrative: WHILE ON APCH TO LAX ON THE SEAVU1 EXPECTING THE ILS RWY 25R; APCH CHANGED OUR RWY TO RWY 24R. THE FMC BECAME VERY DIFFICULT TO UPDATE WITH EXTENDED PERIODS OF A BLANK FMC OR A 'STANDBY ONE' MESSAGE DISPLAYED. SOME WAYPOINTS OF THE NEW ARR WERE MISSING AND HAD TO BE INPUT MANUALLY. ONCE ESTABLISHED ON THE NEW ARR THE FMC SHOWED THE ACFT IN LNAV BUT N OF COURSE AND NOT CORRECTING. MANUAL CORRECTIONS WERE APPLIED TO AN UNEVENTFUL APCH AND LNDG. NO DEVS WERE NOTED BY ATC.

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.