Narrative:

Correct runway; runway intersection; and departure were programmed in FMS and verified during pre-takeoff check. A pre-takeoff FMS quick align was not required. We departed lfpg runway 18L from the S1 intersection via the bubli 1H LNAV departure. Shortly after takeoff; we noted an LNAV capture and the flight director directed a turn to the left. We began very slight turn to left using approximately 5 degrees of bank. We turned approximately 5 degrees left of runway heading. Although hesitant to turn toward the parallel departures to the north; I believed that the flight director was commanding a very minor correction to the LNAV (straight out) course. When left turn guidance continued; I realized that steering guidance was in error and after a few seconds; discontinued our slight turn to the left. Lfpg tower then assigned a 110 degree vector. We then noted that the FMS map and departure track was significantly shifted (approximately 1 to 2 miles north) and determined that a runway update had not occurred during takeoff roll. As we continued on the tower assigned vector; the FMS map corrected itself within approximately 2 minutes. We used raw data to verify that the FMS map was now accurate; and eventually received clearance and proceeded direct to bubli fix using LNAV. No other FMS or map discrepancies were noted for the remainder of the flight.callback conversation with reporter revealed the following information: reporter stated that updated software in the FMC does not require the crew to manually update the aircraft position when taking the runway; it is assumed to be automatically updated by the aircraft/FMC at power up. Reporter stated that he has flown 3 different aircraft on 3 different occasions from lfpg on the same departure and indicated that the magenta line and initial fix were off center from where it should have been with regard to the departure and he briefed his crew to be aware that when LNAV is selected for flight director guidance be prepared to select heading in order to comply with the departure. Reporter added that in all cases; the aircraft would have turned or did turn to meet the magenta line. After several seconds/minutes; the FMC would determine its position (DME fixing) and correct its known position. Reporter stated he felt that there may be a software problem with the lfpg departure considering that it has occurred 3 times with him flying.

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Original NASA ASRS Text

Title: B767-300 FLT CREW HAS A HDG DEV DURING LNAV RWY 8L BUBLI H.

Narrative: CORRECT RWY; RWY INTXN; AND DEP WERE PROGRAMMED IN FMS AND VERIFIED DURING PRE-TKOF CHK. A PRE-TKOF FMS QUICK ALIGN WAS NOT REQUIRED. WE DEPARTED LFPG RWY 18L FROM THE S1 INTXN VIA THE BUBLI 1H LNAV DEP. SHORTLY AFTER TKOF; WE NOTED AN LNAV CAPTURE AND THE FLT DIRECTOR DIRECTED A TURN TO THE L. WE BEGAN VERY SLIGHT TURN TO L USING APPROX 5 DEGS OF BANK. WE TURNED APPROX 5 DEGS L OF RWY HDG. ALTHOUGH HESITANT TO TURN TOWARD THE PARALLEL DEPS TO THE N; I BELIEVED THAT THE FLT DIRECTOR WAS COMMANDING A VERY MINOR CORRECTION TO THE LNAV (STRAIGHT OUT) COURSE. WHEN L TURN GUIDANCE CONTINUED; I REALIZED THAT STEERING GUIDANCE WAS IN ERROR AND AFTER A FEW SECONDS; DISCONTINUED OUR SLIGHT TURN TO THE L. LFPG TWR THEN ASSIGNED A 110 DEG VECTOR. WE THEN NOTED THAT THE FMS MAP AND DEP TRACK WAS SIGNIFICANTLY SHIFTED (APPROX 1 TO 2 MILES N) AND DETERMINED THAT A RWY UPDATE HAD NOT OCCURRED DURING TKOF ROLL. AS WE CONTINUED ON THE TWR ASSIGNED VECTOR; THE FMS MAP CORRECTED ITSELF WITHIN APPROX 2 MINUTES. WE USED RAW DATA TO VERIFY THAT THE FMS MAP WAS NOW ACCURATE; AND EVENTUALLY RECEIVED CLRNC AND PROCEEDED DIRECT TO BUBLI FIX USING LNAV. NO OTHER FMS OR MAP DISCREPANCIES WERE NOTED FOR THE REMAINDER OF THE FLT.CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: RPTR STATED THAT UPDATED SOFTWARE IN THE FMC DOES NOT REQUIRE THE CREW TO MANUALLY UPDATE THE ACFT POSITION WHEN TAKING THE RWY; IT IS ASSUMED TO BE AUTOMATICALLY UPDATED BY THE ACFT/FMC AT POWER UP. RPTR STATED THAT HE HAS FLOWN 3 DIFFERENT ACFT ON 3 DIFFERENT OCCASIONS FROM LFPG ON THE SAME DEP AND INDICATED THAT THE MAGENTA LINE AND INITIAL FIX WERE OFF CTR FROM WHERE IT SHOULD HAVE BEEN WITH REGARD TO THE DEP AND HE BRIEFED HIS CREW TO BE AWARE THAT WHEN LNAV IS SELECTED FOR FLT DIRECTOR GUIDANCE BE PREPARED TO SELECT HDG IN ORDER TO COMPLY WITH THE DEP. RPTR ADDED THAT IN ALL CASES; THE ACFT WOULD HAVE TURNED OR DID TURN TO MEET THE MAGENTA LINE. AFTER SEVERAL SECONDS/MINUTES; THE FMC WOULD DETERMINE ITS POSITION (DME FIXING) AND CORRECT ITS KNOWN POSITION. RPTR STATED HE FELT THAT THERE MAY BE A SOFTWARE PROBLEM WITH THE LFPG DEP CONSIDERING THAT IT HAS OCCURRED 3 TIMES WITH HIM FLYING.

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.