B777-200
Flight Crew Multiengine; Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP)
Other / Unknown
Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Flight Crew Regained Aircraft Control
Weather
Crew flying at the time encountered severe turbulence at FL310. Aircraft gained 340 feet and had a speed reduction of around 20 knots. I was in the supernumerary compartment at the time. This was all info give to me by the crew who were flying at the time.
Two back to back severe turbulence encounters at FL310. While at cruise just on top of a high cloud layer; we experienced severe turbulence in two back to back encounters. Aircraft felt like it hit a wall of wind shear and was thrown up 340 feet. Very violent. Somehow; autopilot stayed engaged. Airspeed went down just to the foot. Aircraft immediately started to correct back down to altitude regaining airspeed. Shortly thereafter a second encounter almost as severe as the first occurred. Aircraft handled it in the same way. Mach .82 at 685;000 pounds gross weight. Never have I felt anything quite like this. As Pilot Monitoring; I immediately reported this to Tokyo Control knowing [company aircraft] was right behind us. They offset; but unfortunately still encountered the same severe turbulence. Many aircraft on the frequency were concerned about their flight path and Tokyo Control somehow was confused so I began to repeatedly report the LAT/LONG position of outrage encounter so they could avoid. Not impressed with Tokyo Control. Reported [to Operations] also. Both encounters caused a very brief instant stick shaker of only momentary activation. We were ready to take action but aircraft recovered very nicely with autopilot remaining on.There were no warnings. We were clear of any convective activity; well above returns below. I also had the EFVS on in cruise; something I learned going to South America at night over the Amazon during a moonless night as being useful. Severe Turb warnings [Operations] had dutifully provided were no where near this location. We could not avoid this.
B777-200 flight crew reported encountering several and un-forecasted clear air turbulence incidents during cruise.