Narrative:

In preparation for upcoming scheduled crew change at xa:31 the first officer (first officer) requested a wind update at approximately xa:18. At xa:21 we called fb/fc with ten minute wake-up call. A few minutes later wind load appeared on the FMC. The first officer confirmed; loaded and executed the winds. We were approximately 170 miles east of zzzzz and 370 miles west of [coordinate X]. After loading and executing the winds the aircraft initiated an immediate right turn eventually rolling up to approximately 20 degrees of bank. I immediately selected heading select to initiate a left turn back on course. The aircraft deviated approximately one-half mile right of the strategic lateral offset procedure (slop) offset. I noticed a magenta dashed line on the nd extending off our next (supposed to be current active) waypoint. The extension of the magenta dashed line off of [coordinate X] was to the left at about a 260 degree radial from [coordinate X]. The nd also showed two additional dashed blue lines extending forward from our aircraft position (pictures taken of nd). The FMC legs page now displayed [coordinate Y] as our current active waypoint; not [coordinate X] which was the next point in front of our position and where we were navigating to prior to loading the winds. The position report page of the FMC displayed position as [coordinate X] and an air traffic area of xa:22 and an EST for [coordinate X] of an ETA of xb:06. Our correct ETA for [coordinate X] was xb:06. We activated route 2 legs since our current active waypoint; [coordinate X]; had disappeared from the route 1 legs page. At this point the fb/fc returned to the flight deck. Shortly thereafter we received an ATC message asking that we 'check FMS and correct active waypoint'. The first officer; fb; fc and I all verified our course was now correct and we re-intercepted LNAV course to [coordinate X]. Shortly thereafter we saw weather ahead and requested deviation around weather. The weather deviation was approved. We briefed the fb and fc on what occurred and they continued deviation around weather and the first officer and I went on break. Later in the flight after the completion of the oceanic crossing we updated winds again with no issues. At no time during the loss of LNAV and our current active waypoint did we deviate more than one-half mile off course. After we were established back on course to [coordinate X] and it once again became our active waypoint we received no other requests from ATC.

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Original NASA ASRS Text

Title: Air Carrier Captain reported shortly after updating winds aloft the FMS commanded a turn off course. The First Officer reported this was a known anomaly issued from the aircraft manufacture.

Narrative: In preparation for upcoming scheduled crew change at XA:31 the First Officer (FO) requested a wind update at approximately XA:18. At XA:21 we called FB/FC with ten minute wake-up call. A few minutes later wind load appeared on the FMC. The FO confirmed; loaded and executed the winds. We were approximately 170 miles east of ZZZZZ and 370 miles west of [coordinate X]. After loading and executing the winds the aircraft initiated an immediate right turn eventually rolling up to approximately 20 degrees of bank. I immediately selected heading select to initiate a left turn back on course. The aircraft deviated approximately one-half mile right of the Strategic Lateral Offset Procedure (SLOP) offset. I noticed a magenta dashed line on the ND extending off our next (supposed to be current active) waypoint. The extension of the magenta dashed line off of [coordinate X] was to the left at about a 260 degree radial from [coordinate X]. The ND also showed two additional dashed blue lines extending forward from our aircraft position (pictures taken of ND). The FMC Legs page now displayed [coordinate Y] as our current active waypoint; not [coordinate X] which was the next point in front of our position and where we were navigating to prior to loading the winds. The POS Report page of the FMC displayed POS as [coordinate X] and an ATA of XA:22 and an EST for [coordinate X] of an ETA of XB:06. Our correct ETA for [coordinate X] was XB:06. We activated RTE 2 Legs since our current active waypoint; [coordinate X]; had disappeared from the RTE 1 Legs page. At this point the FB/FC returned to the flight deck. Shortly thereafter we received an ATC message asking that we 'CHK FMS and Correct Active Waypoint'. The FO; FB; FC and I all verified our course was now correct and we re-intercepted LNAV course to [coordinate X]. Shortly thereafter we saw weather ahead and requested deviation around weather. The weather deviation was approved. We briefed the FB and FC on what occurred and they continued deviation around weather and the FO and I went on break. Later in the flight after the completion of the oceanic crossing we updated winds again with no issues. At no time during the loss of LNAV and our current active waypoint did we deviate more than one-half mile off course. After we were established back on course to [coordinate X] and it once again became our active waypoint we received no other requests from ATC.

Data retrieved from NASA's ASRS site 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.