Narrative:

Approximately at X airway we encountered what I would term continuous moderate occasional severe turbulence. We had previously sat the passengers down when we had light turbulence and we instructed the flight attendants to be seated immediately via PA. Captain and flying first officer were in bunk on their sleep shift. We left the autopilot hooked up to help with control but the typical slow throttle corrections had me overriding the thrust settings to keep us out of the over speed and stall regions. We were initially at FL370 but requested climb to FL390 as we thought we may get out of the turbulence because of the forecast (FL310-370) although this forecast ended about X airway. Optimal according to the FMC was approximately FL390. When we finally attained clearance (cpdlc) and climbed it was actually worse and only reduced our margins. The whole event was probably 10-15 minutes. Aircraft control was maintained although the auto pilot was having a difficult time maintaining level flight. I was ready to take over if it kicked off but felt overall it helped to have the auto pilot on. We then asked for FL350 but it took over 3 minutes to get this approved (cpdlc and HF). The biggest threat I felt was the airspeed changes with violent wind shifts and different velocity of the wind. We never had an over speed although we were close many times but we had it go into the slow range above stall many times and I was concerned about stalling out this aircraft several times. Near the end of the event we had the low hydraulic quantity #1 EICAS. By the time we got to the checklist though we had lost all fluid and pressure (couple minutes with altitude changes; reports to HF; VHF for aircraft behind us; etc). When this happened my auto pilot kicked off but I changed to the left auto pilot as well as my source select switch for the flight director. We alerted the captain to come out of the bunk area and we handled the resulting checklists and landed uneventfully at our destination [which was] also the nearest suitable airport. Note: sigmet came out after our PIREP.

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Original NASA ASRS Text

Title: B747 First Officer reported they lost Number 1 Hydraulic System at the same time they were dealing with moderate to severe turbulence.

Narrative: Approximately at X Airway we encountered what I would term continuous moderate occasional severe turbulence. We had previously sat the passengers down when we had light turbulence and we instructed the flight attendants to be seated immediately via PA. Captain and Flying First officer were in bunk on their sleep shift. We left the autopilot hooked up to help with control but the typical slow throttle corrections had me overriding the thrust settings to keep us out of the over speed and stall regions. We were initially at FL370 but requested climb to FL390 as we thought we may get out of the turbulence because of the forecast (FL310-370) although this forecast ended about X Airway. Optimal according to the FMC was approximately FL390. When we finally attained clearance (CPDLC) and climbed it was actually worse and only reduced our margins. The whole event was probably 10-15 minutes. Aircraft control was maintained although the Auto Pilot was having a difficult time maintaining level flight. I was ready to take over if it kicked off but felt overall it helped to have the Auto Pilot on. We then asked for FL350 but it took over 3 minutes to get this approved (CPDLC and HF). The biggest threat I felt was the airspeed changes with violent wind shifts and different velocity of the wind. We never had an over speed although we were close many times but we had it go into the slow range above stall many times and I was concerned about stalling out this aircraft several times. Near the end of the event we had the low hydraulic quantity #1 EICAS. By the time we got to the checklist though we had lost all fluid and pressure (couple minutes with altitude changes; reports to HF; VHF for aircraft behind us; etc). When this happened my Auto Pilot kicked off but I changed to the left Auto Pilot as well as my source select switch for the Flight Director. We alerted the Captain to come out of the bunk area and we handled the resulting checklists and landed uneventfully at our destination [which was] also the nearest suitable airport. Note: Sigmet came out after our PIREP.

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.