CE680 captain reported loss of aircraft control due to severe turbulence during cruise.

Attributes
ACN	1610920
Time
Date	201901
Local Time Of Day	0001-0600
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	Citation Latitude (C680A)
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Pilot Flying First Officer
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Inflight Event / Encounter Weather / Turbulence Inflight Event / Encounter Loss Of Aircraft Control

Narrative:

Severe turbulence encountered during arrival into ZZZ. At 36;000 ft and approximately .72M we encountered strong mountain wave type activity and a rapid uncontrolled descent. Autopilot came off and we were able to keep the wings somewhat level. Pilot flying was pulling back forcefully on the control wheel but we were still descending at 4000 ft/min. Pilot monitoring deployed the speed brakes but speed kept increasing. Finally regained control after losing 4;000 feet of altitude.

Original NASA ASRS Text

Title: CE680 Captain reported loss of aircraft control due to severe turbulence during cruise.

Narrative: Severe turbulence encountered during arrival into ZZZ. At 36;000 FT and approximately .72M we encountered strong mountain wave type activity and a rapid uncontrolled descent. Autopilot came off and we were able to keep the wings somewhat level. Pilot flying was pulling back forcefully on the control wheel but we were still descending at 4000 ft/min. Pilot Monitoring deployed the speed brakes but speed kept increasing. Finally regained control after losing 4;000 feet of altitude.

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.