B777-200 flight crew reported encountering several and un-forecasted clear air turbulence incidents ...

Attributes
ACN	1588336
Time
Date	201810
Local Time Of Day	0001-0600
Place
Locale Reference	RJJJ.ARTCC
State Reference	FO
Environment
Flight Conditions	VMC
Aircraft 1
Make Model Name	B777-200
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Pilot Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine Flight Crew Instrument
Person 2
Function	Pilot Not Flying First Officer
Qualification	Flight Crew Commercial Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Published Material / Policy Deviation - Speed All Types Inflight Event / Encounter Weather / Turbulence

Narrative:

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.

Original NASA ASRS Text

Title: B777-200 flight crew reported encountering several and un-forecasted clear air turbulence incidents during cruise.

Narrative: 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.

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.