Narrative:

We were on our second leg of the night flying from ZZZZ-ZZZZ1. We were east of vietnam and in contact with hochi minh control both with VHF and cpdlc. We were maintaining FL350 with another aircraft flying in the same direction (eastbound) at FL360 on our same airway. We experienced two times light wake turbulence from this aircraft and we communicated to vvts that we were requesting 2NM right of track due to that turbulence. Both times we received no reply from vvts control. A few minutes later (about 20nm east of position dudis) we experienced a more severe wake turbulence encounter. The aircraft was pitching and rolling abruptly at that time. The bank was going past 30 degrees and probably more at the point.I disconnected the autopilot and initiated control of the aircraft. At that point the wake turbulence got more severe and I came out of my seat repeatedly. In attempts to perform the upset recovery it was difficult to maintain control and manipulate the MCP (mode control panel). At this time it was very difficult to even read the flight instruments due to the severe turbulence. In the recovery we lost about 800 ft. And our altitude was fl 342 until a recovery to altitude could be initiated with manipulation of the MCP.it has to be said that during the beginning of the more severe event we tried several times (more than 10 times) to call vvts via VHF requesting a right of track deviation. To no avail. Only until the captain made a more [forceful] request did we get a reply from vvts control. We informed vvts of our altitude and our recovery back to fl 350. There were no events after the recovery to altitude. Flight proceeded as normal.

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Original NASA ASRS Text

Title: B767-300 flight crew on an international flight reported loss of control at FL350 from a wake turbulence encounter with an aircraft ahead of them at FL360.

Narrative: We were on our second leg of the night flying from ZZZZ-ZZZZ1. We were east of Vietnam and in contact with HoChi Minh Control both with VHF and CPDLC. We were maintaining FL350 with another aircraft flying in the same direction (Eastbound) at FL360 on our same airway. We experienced two times light wake turbulence from this aircraft and we communicated to VVTS that we were requesting 2NM right of track due to that turbulence. Both times we received no reply from VVTS control. A few minutes later (about 20nm East of position Dudis) we experienced a more severe wake turbulence encounter. The aircraft was pitching and rolling abruptly at that time. The bank was going past 30 degrees and probably more at the point.I disconnected the autopilot and initiated control of the aircraft. At that point the wake turbulence got more severe and I came out of my seat repeatedly. In attempts to perform the upset recovery it was difficult to maintain control and manipulate the MCP (Mode Control Panel). At this time it was very difficult to even read the flight instruments due to the severe turbulence. In the recovery we lost about 800 ft. and our altitude was FL 342 until a recovery to altitude could be initiated with manipulation of the MCP.It has to be said that during the beginning of the more severe event we tried several times (more than 10 times) to call VVTS via VHF requesting a right of track deviation. To no avail. Only until the Captain made a more [forceful] request did we get a reply from VVTS control. We informed VVTS of our altitude and our recovery back to FL 350. There were no events after the recovery to altitude. Flight proceeded as normal.

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.