Narrative:

There was rain and thunderstorm activity at both the departure and arrival airport. During the initial climb out wing/stab; nacelle; windshield heat were turned on along with the igniters passing through 15;000 feet +10 degrees. After level off at 41;000 ft the autopilot was noticeably struggling to make smooth heading changes and was going up and down + or - 200 ft. I tried switching from yaw damp number 1 to number 2; air data computer number 1 to number 2; I tried heading mode; flying faster; I even was hand flying with a lot of difficulty while switching between the various modes. Left pitot heat circuit breaker (circuit breaker) was found popped and so I reset it. This did not help stabilize the airplane. I felt that perhaps we had airframe icing and were too heavy for FL410 and requested a descent to FL350. ATC cleared us to FL370 and once we leveled off there the airplane was flying noticeably smoother. I then asked for that as our final altitude and we continued the flight. For troubleshooting purposes we tried yd number 1 again and found it to be unreliable. My ball kicked out approximately 1/2 ball and the airplane began to dutch roll side to side and climb and descend 100 - 150 feet. Yd number 2 was selected again and I continued the flight thinking that we must be heavy due to airframe icing and that yd number 1 needed to get written up.there was a line of thunderstorms directly ahead of us. Both [the first officer (first officer)] and I were watching them as we approached and determined that we were above it. We were told to cross [an intersection] at 13;000 ft. I told [the first officer] and she told ATC that we would hold off on our descent until we passed a good size cell on our route. As we approached the cell I noticed we were too low and asked [the first officer] to ask for a climb to FL390. I turned on the seat belt sign knowing things could be getting rough soon; along with all anti ice systems. This request was not immediately made with ATC and as a result we entered IMC. The clearance was given and I began a climb; it was very rough; lightning flashes were all around us with moderate turbulence. Then it happened....my airspeed was accelerating and we were shooting up like a rocket; faster and faster and my airspeed was increasing; I pulled off some power and pitched up even further; thinking we had a great updraft. [The first officer] said: 'speed' and so I reduced the thrust even more and pitched up even more; the second time she said 'speed' I went to idle and pitched up aggressively to over 30 degrees; I then looked over at her side and saw our airspeed now at 110 knots and just then the pusher activated as the aircraft stalled. I now pushed up power and tried to gently raise the nose but the pusher stopped helping me push and we were too slow and trimmed too nose up and a secondary stall happened. We were still in IMC and getting bumped around with several updrafts and downdrafts adding to the situation. I told [the first officer] I was not sure what altitude we were now at and wanted to clear any airspace around us. As [the first officer] was doing so I looked at her airspeed and altimeter and I could see we had recovered and were in smooth descent through FL350. ATC asked her to say again. She did so and attended to the passengers in the back; trying to calm them down who were obviously upset.we exited the cell and within minutes my airspeed and altimeter came back as we were out of the ice. I looked around the t-handle and sure enough saw left pitot heat light glaring. I looked down and saw the circuit breaker popped again. I considered giving the flight controls to [the first officer] but I was not sure of her state of mind. I was calm and happy to have figured out what had happened because it had came as a surprise for me. We were out of visible moisture and once the sat was above 10 degrees I turned off all the anti-ice. We completed the ILS without any further issues.

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Original NASA ASRS Text

Title: Learjet 35 Captain reported stalling the aircraft at FL370 when his airspeed indicator began to read erroneously high with the failure of the L pitot heat.

Narrative: There was rain and thunderstorm activity at both the departure and arrival airport. During the initial climb out wing/stab; nacelle; windshield heat were turned on along with the igniters passing through 15;000 feet +10 degrees. After level off at 41;000 FT the autopilot was noticeably struggling to make smooth heading changes and was going up and down + or - 200 FT. I tried switching from yaw damp Number 1 to Number 2; ADC Number 1 to Number 2; I tried HDG mode; flying faster; I even was hand flying with a lot of difficulty while switching between the various modes. Left pitot heat Circuit Breaker (CB) was found popped and so I reset it. This did not help stabilize the airplane. I felt that perhaps we had airframe icing and were too heavy for FL410 and requested a descent to FL350. ATC cleared us to FL370 and once we leveled off there the airplane was flying noticeably smoother. I then asked for that as our final altitude and we continued the flight. For troubleshooting purposes we tried YD Number 1 again and found it to be unreliable. My ball kicked out approximately 1/2 ball and the airplane began to Dutch roll side to side and climb and descend 100 - 150 feet. YD Number 2 was selected again and I continued the flight thinking that we must be heavy due to airframe icing and that YD Number 1 needed to get written up.There was a line of thunderstorms directly ahead of us. Both [the First Officer (FO)] and I were watching them as we approached and determined that we were above it. We were told to cross [an intersection] AT 13;000 FT. I told [the FO] and she told ATC that we would hold off on our descent until we passed a good size cell on our route. As we approached the cell I noticed we were too low and asked [the FO] to ask for a climb to FL390. I turned on the seat belt sign knowing things could be getting rough soon; along with all anti ice systems. This request was not immediately made with ATC and as a result we entered IMC. The clearance was given and I began a climb; it was very rough; lightning flashes were all around us with moderate turbulence. Then IT happened....My airspeed was accelerating and we were shooting up like a rocket; faster and faster and my airspeed was increasing; I pulled off some power and pitched up even further; thinking we had a great updraft. [The FO] said: 'SPEED' and so I reduced the thrust even more and pitched up even more; the second time she said 'Speed' I went to idle and pitched up aggressively to over 30 degrees; I then looked over at her side and saw our airspeed now at 110 knots and just then the pusher activated as the aircraft stalled. I now pushed up power and tried to gently raise the nose but the pusher stopped helping me push and we were too slow and trimmed too nose up and a secondary stall happened. We were still in IMC and getting bumped around with several updrafts and downdrafts adding to the situation. I told [the FO] I was not sure what altitude we were now at and wanted to clear any airspace around us. As [the FO] was doing so I looked at her airspeed and altimeter and I could see we had recovered and were in smooth descent through FL350. ATC asked her to say again. She did so and attended to the Passengers in the back; trying to calm them down who were obviously upset.We exited the cell and within minutes my airspeed and altimeter came back as we were out of the ice. I looked around the T-handle and sure enough saw L pitot heat light glaring. I looked down and saw the CB popped again. I considered giving the flight controls to [the FO] but I was not sure of her state of mind. I was calm and happy to have figured out what had happened because it had came as a surprise for me. We were out of visible moisture and once the SAT was above 10 degrees I turned off all the anti-ice. We completed the ILS without any further issues.

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.