Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Flight Crew Last 90 Days 204; Flight Crew Total 21263; Flight Crew Type 3022
Human-Machine Interface; Communication Breakdown
Deviation - Track / Heading All Types; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Provided Assistance; Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Overcame Equipment Problem; Flight Crew Returned To Clearance
Procedure; Human Factors
Aircraft was approaching [coordinates] in continuous moderate turbulence. First Officer began to plot new turbulence report utilizing Rte 2 page. Shortly afterwards; Captain became aware that the aircraft was showing significantly RIGHT of course from magenta line. A turn to the left was executed in order to rejoin the established course. Shortly after turn initiated; ZZZ [ATC] contacted flight with information that it was deviating LEFT of course and issued clearance to deviate as necessary. Captain became concerned as to the accuracy of magenta course being displayed on moving map and a direct course to [coordinates] was then executed and a new position report sent. A careful examination of flight plan was made and compared to loaded route. Waypoints; distances and courses were carefully verified. Flight proceeded to [destination] normally. It would appear that that during the plotting of the turbulence that Route 2 was inadvertently activated. How this happened is not known.
Relief Pilot and I found out about the occurrence during the post flight debrief. As a member of the crew; we felt we should submit as well. I can attest to the rough ride and know the pilots were trying to avoid an area of forecast turbulence.
B787 flight crew reported flight plan course deviation by inadvertently activated secondary route in the FMS.