Learjet 45
Flight Crew Instrument; Flight Crew Flight Instructor; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 70; Flight Crew Total 4000; Flight Crew Type 1500
Deviation - Altitude Excursion From Assigned Altitude; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Flight Crew Returned To Clearance; Flight Crew Regained Aircraft Control
Weather
In cruise at FL400 encountered moderate turbulence.  We asked to descend to FL380 and Washington Center approved the request.  As we initiated the descent; the turbulence increased and caused us to uncontrollably climb at a rate of up to 2500 feet per minute for 20 to 30 seconds. I immediately instructed my first officer to advise ATC we were in an uncontrolled climb. It was not until 41;200 feet we were able to arrest the climb and reinitiate the descent.  As we passed back through FL400 again the turbulence started to decrease our descent rate but was not strong enough to cause us to climb again. We leveled at FL380 and had a smooth ride and continued the flight as normal.
The jolts we felt would be described as only moderate turbulence; however due to the uncontrolled climb I advised center of severe turbulence. There were no injuries and the flight continued without further incident.
Lear 45 flight crew reported an uncontrolled climb to FL412 from FL400 as a result of moderate to severe turbulence.