Narrative:

We were flying at FL410 on a ferry leg. The radar was on and we were monitoring the weather ahead. We had discussed routing to avoid the large cells ahead and had placed the seatbelt on so that the flight attendant would be seated in case of rough air. We had deviated to the south of our original route and were approximately 20 miles south of the large cell. As we approach the area we commented on how steep the gradient was on the radar return. Additionally we noted that we were up wind of the cell with the wind out of the south at approximately 30 to 40 kts. We were well south of the radar returns when we encountered moderate to severe turbulence. At the onset of this event I saw the nose yaw rapidly to the left; the nose began to rise and the aircraft started [to] gain altitude. I disengaged the autopilot but was unable to initially control the pitch. The aircraft rolled rolled left in a 20 to 25 degree angle but I was able to easily correct the bank angle. Before I was able to regain control of the pitch the aircraft climbed almost 600 ft. The captain informed ATC of our situation and requested a block altitude and was granted FL390 to FL430 for the area that we were in. Shortly after we were able to regain control of the pitch and level the aircraft at FL410. Other than the cell off to the left of the aircraft we had no other returns on the radar. The duration of this event from start to finish was approximately 60 seconds. While we followed standard thunderstorm avoidance guidance in this case it was not enough separation. We were prepared for some rough air but not an upset at 41000 ft. It would perhaps be beneficial for upset training to be conducted at high altitudes to include high altitude stalls at or near aircraft service ceilings.

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Original NASA ASRS Text

Title: A Fractional Jet Crew described a moderate to severe turbulence encounter at FL410 which resulted in an uncontrolled 600 ft altitude increase upwind and 20 miles from the nearest cell.

Narrative: We were flying at FL410 on a ferry leg. The radar was on and we were monitoring the weather ahead. We had discussed routing to avoid the large cells ahead and had placed the seatbelt on so that the flight attendant would be seated in case of rough air. We had deviated to the south of our original route and were approximately 20 miles south of the large cell. As we approach the area we commented on how steep the gradient was on the radar return. Additionally we noted that we were up wind of the cell with the wind out of the south at approximately 30 to 40 kts. We were well south of the radar returns when we encountered moderate to severe turbulence. At the onset of this event I saw the nose yaw rapidly to the left; the nose began to rise and the aircraft started [to] gain altitude. I disengaged the autopilot but was unable to initially control the pitch. The aircraft rolled rolled left in a 20 to 25 degree angle but I was able to easily correct the bank angle. Before I was able to regain control of the pitch the aircraft climbed almost 600 ft. The captain informed ATC of our situation and requested a block altitude and was granted FL390 to FL430 for the area that we were in. Shortly after we were able to regain control of the pitch and level the aircraft at FL410. Other than the cell off to the left of the aircraft we had no other returns on the radar. The duration of this event from start to finish was approximately 60 seconds. While we followed standard thunderstorm avoidance guidance in this case it was not enough separation. We were prepared for some rough air but not an upset at 41000 ft. It would perhaps be beneficial for upset training to be conducted at high altitudes to include high altitude stalls at or near aircraft service ceilings.

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.