B777 flight crew reported they had 'no control of airspeed or altitude for about one minute' during ...

Attributes
ACN	1523363
Time
Date	201803
Local Time Of Day	0001-0600
Place
Locale Reference	BIRD.ARTCC
State Reference	FO
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	B777 Undifferentiated or Other Model
Operating Under FAR Part	Part 121
Flight Phase	Climb
Flight Plan	IFR
Person 1
Function	Pilot Not Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Total 14990 Flight Crew Type 2141
Person 2
Function	Pilot Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Speed All Types Inflight Event / Encounter Loss Of Aircraft Control

Narrative:

Several aircraft below our altitude had reported severe turbulence. We were at FL370 with moderate turbulence. We started a climb to FL390; [but] at FL378 we had lost positive control of the airspeed. No limits of airspeed were exceed either low or high. We started back down to FL370 with an immediate ATC clearance to descend. Upon attempting to start the descent we discovered we had no control of our altitude. In flch with the throttles at idle the aircraft would not descend. We were simply riding mountain wave that prevented descending. After approximately 1 minute the aircraft began a descent that rapidly took us back to FL370. No violent turbulence was encounter. We had no control of airspeed or altitude for about one minute. There were no wsi fpgs for turbulence for our route of flight in this area. As I recall the static air temperature seemed warmer than normal to me for that altitude and time of year.

Original NASA ASRS Text

Title: B777 flight crew reported they had 'no control of airspeed or altitude for about one minute' during a mountain wave encounter at FL380 in the vicinity of Iceland.

Narrative: Several aircraft below our altitude had reported severe turbulence. We were at FL370 with moderate turbulence. We started a climb to FL390; [but] at FL378 we had lost positive control of the airspeed. No limits of airspeed were exceed either low or high. We started back down to FL370 with an immediate ATC clearance to descend. Upon attempting to start the descent we discovered we had no control of our altitude. In FLCH with the throttles at idle the aircraft would not descend. We were simply riding mountain wave that prevented descending. After approximately 1 minute the aircraft began a descent that rapidly took us back to FL370. No violent turbulence was encounter. We had no control of airspeed or altitude for about one minute. There were no WSI FPGs for turbulence for our route of flight in this area. As I recall the Static Air Temperature seemed warmer than normal to me for that altitude and time of year.

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.

B777 flight crew reported they had 'no control of airspeed or altitude for about one minute' during a mountain wave encounter at FL380 in the vicinity of iceland.