Commercial Fixed Wing
Flight Crew Air Transport Pilot (ATP)
Human-Machine Interface; Troubleshooting; Distraction
Aircraft Equipment Problem Less Severe; Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued Advisory / Alert; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Overcame Equipment Problem; Flight Crew FLC Overrode Automation
Aircraft
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.
I was FB on rest break when event happened. The FC and I returned to the flight deck just after event occurred. Captain briefed us on the event. We were on a random oceanic route in ZZZZ FIR. The First officer (FO) requested new wind data to update the FMC. After loading the uplinked winds the aircraft began an uncommanded right turn off track. The current active waypoint [coordinate X] was replaced by the next waypoint on our route; [coordinate Y]. Captain intervened with heading select and worked to re-intercept the proper course by updating and activating route 2. He made sure we all agreed that the aircraft was back on the cleared route and the waypoints verified before completing the crew change briefing and leaving the flight deck for his rest break. It appeared that we were less than .5 mile right of track before returning to course. We experienced no further issues after that. This is a known anomaly that was supposedly fixed by [the manufacturer]. However it was different from previous events of this type in that we were not near any route waypoints when it happened. We were 100+ miles from our last waypoint and 300+ miles to the active waypoint. Suggestions: a renewed awareness by pilots and a positive fix by [manufacturer].
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.