Two air carrier pilots on break reported noticing the effects of possible wake turbulence on their trans-Pacific flight.
Synopsis
Two air carrier pilots on break reported noticing the effects of possible wake turbulence on their trans-Pacific flight.
Narrative
We were flying over the Pacific Ocean where we were on a filed track that everyone else seemed to be on. We had noticed a few other aircraft in front of us at differing altitudes through at least the first half of the flight. While I was upfront for the first half; we had to adjust our SLOP (Strategic Lateral Offset Procedure) a few times to account for the winds and what we can see the other aircraft doing utilizing TCAS and their respective contrails. Prior to the event; we had swapped in the [Relief Pilot] so that the Captain (CA) and I can take our break prior to landing. At the time of the swap; the weather outside was VMC and we were clear of any clouds nearby. We were cruising at FL350; having stepped climbed according to the VNAV CRZ page; at the filed cost index ECON speeds. However; there was a bend in the jet stream right around that time to swap. I had just laid down and strapped myself in when we hit the first bump.I did hear a PA be made within a second of it which I presume is the turbulence PA for the Flight Attendants (FAs). I am not sure which one since it wasn't broadcasted into the bunk room so it was muffled. It was clearly in the moderate category maybe a bit higher at certain points of the event based off of my motion laying down under the seat belt in a dark bunk. The motion of the turbulence did feel like wake turbulence to me and therefore; out of curiosity and since I was on break; I utilized the WIFI to see what was up in front of us. On the app; I saw that there was an aircraft in front of us and only 1;000 feet above our current altitude. I heard the Captain (CA) pick the phone up in the seating area and I told him about what I had found to suggest that we could've possibly had a wake turbulence encounter and to maybe relay to the [Relief Pilot] in the flight deck for increased situational awareness.
Second reporter narrative
Just after the half way point in our flight; and shortly after the relief pilots took over; during my rest; the aircraft experienced abrupt moderate or greater turbulence that lasted about 30 to 40 seconds. I had just gotten into the overhead crew rest area and was able to buckle into one of the Jump seats. After the ride smoothed out; I went into the cabin to check on the Flight Attendants and Passengers. The Flight Attendants were shaken; but there were no injuries. I called the flight deck and talked to the relief pilots; who had taken the correct action and had requested a lower altitude to get a smoother ride. The Relief Pilots had contacted Dispatch to report the turbulence and while discussing it they determined that it was possibly wake turbulence from an aircraft that was higher and ahead of us. At the time we were in an area of no forecasted or reported turbulence; we were; however; following SOP and (Strategic Lateral Offset Procedure) SLOP 1 mile right of course. The area we were crossing had multiple fragmented jet streams depicted along our route at different altitudes. During the event; the auto pilot remained engaged; and the aircraft maintained altitude. considering the circumstances; the Relief Pilots did an excellent job and the flight continued without further issue.
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Source: NASA Aviation Safety Reporting System (public domain). Reports are voluntary submissions and are not verified by NASA.