Narrative:

Departing runway 24L; ventura 5 departure; navigation mode. After liftoff; navigation armed immediately. About the time we crossed the 154 degree radial from smo; the aircraft flight director bars began to command a right turn. Unfortunately; I followed the command initially. On the navigation display I noticed an arc going off scale. Not sure what was going on; I shallowed the bank. Shortly thereafter; the navigation display re-indexed and drew a straight line off scale that appeared to be from smo to vtu. At that time we were on about a 280 degree heading. ATC asked our heading as I was turning back to the left. We said heading towards 255 degrees; the controller said maintain heading 250 degrees; which we selected and flown. Once established on the heading; autoplt was selected. At this time I'd estimate we were about 1200 ft; and around 1 mi laterally north of runway track. It was as if the FMGC wanted us to go direct smo; then after we crossed the 154 degree radial the FMGC assumed we had passed the fix and sequenced the route. I did review the flight plan before the departure brief and during the brief. I can't recall 100%; but I don't remember seeing a bad route in the flight plan. I do remember seeing the discontinuity as expected; but I don't recall seeing the initial heading. The navigation display looked accurate during the brief. After landing; the aircraft printed a report indicating an FMGC #1 malfunction; but the time stamp was during landing; not departure. We both wondered if the FMGC #1 malfunctioned and reset incorrectly before resyncing with FMGC #2. Without questions; I don't know how better to describe the incident. The whole occurrence lasted about 45 seconds to 1 min in my estimation. I should have been quicker in my recognition of the FMGC malfunction and selected heading.

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Original NASA ASRS Text

Title: AN AIRBUS PLT DESCRIBES AN FMGC ANOMALY CAUSING A TRACK DEV ON THE LAX VTU 5 SHORTLY AFTER TKOF.

Narrative: DEPARTING RWY 24L; VENTURA 5 DEP; NAV MODE. AFTER LIFTOFF; NAV ARMED IMMEDIATELY. ABOUT THE TIME WE CROSSED THE 154 DEG RADIAL FROM SMO; THE ACFT FLT DIRECTOR BARS BEGAN TO COMMAND A R TURN. UNFORTUNATELY; I FOLLOWED THE COMMAND INITIALLY. ON THE NAV DISPLAY I NOTICED AN ARC GOING OFF SCALE. NOT SURE WHAT WAS GOING ON; I SHALLOWED THE BANK. SHORTLY THEREAFTER; THE NAV DISPLAY RE-INDEXED AND DREW A STRAIGHT LINE OFF SCALE THAT APPEARED TO BE FROM SMO TO VTU. AT THAT TIME WE WERE ON ABOUT A 280 DEG HDG. ATC ASKED OUR HDG AS I WAS TURNING BACK TO THE L. WE SAID HDG TOWARDS 255 DEGS; THE CTLR SAID MAINTAIN HDG 250 DEGS; WHICH WE SELECTED AND FLOWN. ONCE ESTABLISHED ON THE HDG; AUTOPLT WAS SELECTED. AT THIS TIME I'D ESTIMATE WE WERE ABOUT 1200 FT; AND AROUND 1 MI LATERALLY N OF RWY TRACK. IT WAS AS IF THE FMGC WANTED US TO GO DIRECT SMO; THEN AFTER WE CROSSED THE 154 DEG RADIAL THE FMGC ASSUMED WE HAD PASSED THE FIX AND SEQUENCED THE RTE. I DID REVIEW THE FLT PLAN BEFORE THE DEP BRIEF AND DURING THE BRIEF. I CAN'T RECALL 100%; BUT I DON'T REMEMBER SEEING A BAD RTE IN THE FLT PLAN. I DO REMEMBER SEEING THE DISCONTINUITY AS EXPECTED; BUT I DON'T RECALL SEEING THE INITIAL HDG. THE NAV DISPLAY LOOKED ACCURATE DURING THE BRIEF. AFTER LNDG; THE ACFT PRINTED A RPT INDICATING AN FMGC #1 MALFUNCTION; BUT THE TIME STAMP WAS DURING LNDG; NOT DEP. WE BOTH WONDERED IF THE FMGC #1 MALFUNCTIONED AND RESET INCORRECTLY BEFORE RESYNCING WITH FMGC #2. WITHOUT QUESTIONS; I DON'T KNOW HOW BETTER TO DESCRIBE THE INCIDENT. THE WHOLE OCCURRENCE LASTED ABOUT 45 SECONDS TO 1 MIN IN MY ESTIMATION. I SHOULD HAVE BEEN QUICKER IN MY RECOGNITION OF THE FMGC MALFUNCTION AND SELECTED HDG.

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.