Narrative:

Preflight planning included dispatch who relayed 3 separate areas of potential turbulence. The flight was planned initially at FL270 to avoid the first large area of forecast lt-mod turbulence. ATC assigned us FL310 'due traffic'. Flight attendants were briefed to remain seated until we called. Once airborne ATC advised us there were no adverse reports FL310-350. We were experiencing continuous light chop from approximately 12;000-FL27.5. Once level at FL280 we experienced nothing more than occasional light chop. ATC again said no adverse reports FL310-350. I had [the relief officer] call purser so they could start service and secure barrier to allow [the relief officer] to exit cockpit. This occurred approximately 46 minutes after takeoff. We continued to climb to FL310. Autopilot engaged LNAV/VNAV.shortly after level off at FL310 we encountered the first of 2 separate turbulence encounters. The first started as a gentle climb and slight right turn; followed immediately by an immediate left roll and negative pitch change. The autopilot disconnect horn sounded as well as master warning and auto pilot (ap) on electronic attitude director indicators (eadi). Associated with the violent nature of the event my eyeglasses were knocked from my face. I immediately grasped the control wheel with both hands to return the aircraft to level flight. Altitude fluctuated from -300 feet to +600 or 800 feet. Under the circumstances I cannot honestly say what the exact deviations were. I ordered the first officer (first officer) pilot monitoring (pm) to command the flight attendants (flight attendant) to 'be seated immediately'. I was able to return the aircraft to wings level and FL313 when the second and largest of the two jolts of severe occurred. The aircraft again violently pitched up; rolled left; then right; with very little response from the control wheel inputs. I noted approximately 35-40 degrees of left bank and -5 degrees of pitch at one point. It really felt like much more at the time; and actually might have been. The second encounter was quite violent and it was difficult to accurately see the instrument panel. We reported the encounter to [ATC]. There was a bit of a language issue as to what we had encountered as well as trying to get a clearance to a lower altitude. Compounding this was [another air carrier] flight trying to get a different altitude after hearing our report. We were then cleared to FL280. Once we were established in smoother air I made a PA to fas to 'take your jump seats and check in'. Purser reported that there were no injuries. We contacted dispatch via satcom and reported the severe turbulence encounters. [Maintenance] was patched through as well. The decision was made to continue as schedule.

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Original NASA ASRS Text

Title: B777 Captain reported encountering severe turbulence in departure climb.

Narrative: Preflight planning included Dispatch who relayed 3 separate areas of potential turbulence. The flight was planned initially at FL270 to avoid the first large area of forecast LT-MOD Turbulence. ATC assigned us FL310 'due traffic'. Flight Attendants were briefed to remain seated until we called. Once airborne ATC advised us there were no adverse reports FL310-350. We were experiencing continuous light chop from approximately 12;000-FL27.5. Once level at FL280 we experienced nothing more than occasional light chop. ATC again said no adverse reports FL310-350. I had [the relief officer] call Purser so they could start service and secure barrier to allow [the relief officer] to exit cockpit. This occurred approximately 46 minutes after takeoff. We continued to climb to FL310. Autopilot engaged LNAV/VNAV.Shortly after level off at FL310 we encountered the first of 2 separate turbulence encounters. The first started as a gentle climb and slight right turn; followed immediately by an immediate left roll and negative pitch change. The autopilot disconnect horn sounded as well as Master Warning and Auto Pilot (AP) on Electronic Attitude Director Indicators (EADI). Associated with the violent nature of the event my eyeglasses were knocked from my face. I immediately grasped the control wheel with both hands to return the aircraft to level flight. Altitude fluctuated from -300 feet to +600 or 800 feet. Under the circumstances I cannot honestly say what the exact deviations were. I ordered the First Officer (FO) Pilot Monitoring (PM) to command the Flight Attendants (FA) to 'be seated immediately'. I was able to return the aircraft to wings level and FL313 when the second and largest of the two jolts of severe occurred. The aircraft again violently pitched up; rolled left; then right; with very little response from the control wheel inputs. I noted approximately 35-40 degrees of left bank and -5 degrees of pitch at one point. It really felt like much more at the time; and actually might have been. The second encounter was quite violent and it was difficult to accurately see the instrument panel. We reported the encounter to [ATC]. There was a bit of a language issue as to what we had encountered as well as trying to get a clearance to a lower altitude. Compounding this was [another air carrier] flight trying to get a different altitude after hearing our report. We were then cleared to FL280. Once we were established in smoother air I made a PA to FAs to 'take your jump seats and check in'. Purser reported that there were no injuries. We contacted Dispatch via SATCOM and reported the severe turbulence encounters. [Maintenance] was patched through as well. The decision was made to continue as schedule.

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.