Narrative:

There was a massive line of thunderstorms that extended from southwest of sps to over okc up to and beyond missouri. There was; however; a break in the weather between sps and law. We were on a south deviation between these two points at fl 410 when we experienced moderate to severe turbulence. Laterally we were well clear of the storms and encountered no precipitation. Moments after the turbulence began; the autopilot automatically disengaged and would not re-engage. I immediately began to hand fly the aircraft making constant power adjustments to maintain an appropriate airspeed which was rapidly fluctuating up and down due to the turbulence. Though I was initially flying the flight director the aircraft would not maintain altitude due to the turbulence. At this altitude; airspeed; and with the turbulence I was unwilling; for the sake of the safety of flight; to make hard and rapid pitch adjustments to try and reverse the descent. I did; however; hold a steady pitch and power setting that would under normal circumstance given me a climb. Before we were able to contact ATC and notify them of our inability to maintain altitude they contacted us and asked for our altitude; at this point were at approximately fl 395. The copilot responded that we were unable to maintain altitude and ATC cleared us to descend to FL350 and maintain present heading. ATC then asked why we were unable to maintain and I responded that we encountered moderate to severe turbulence and the aircraft was unable to hold altitude. Moments later the turbulence subsided. All of this occurred in approximately under a minute. Also during the turbulence the copilot was constantly calling out descent rates and airspeed. Max descent rate was approximately 2000 fpm and the airspeed fluctuated approximately 30 knots. Between my focus on hand flying the aircraft; my copilot's constant call outs and the busy radio communications due to the weather we were unable to contact ATC as soon as we would have liked to. I believe that the only way I could have maintained altitude would have been rapid and forceful control inputs. At this altitude and with the turbulence I believe this would have jeopardized the safety of flight and the structural integrity of the aircraft. If I was faced with this same scenario again; regardless of whether or the not the aircraft was maintaining altitude; I would immediately request a block altitude in the anticipation of the inability to maintain altitude.

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Original NASA ASRS Text

Title: Upon encountering severe turbulence at FL410; a LJ60 was unable to maintain altitude and airspeed and descended to FL350 after advising ATC.

Narrative: There was a massive line of thunderstorms that extended from southwest of SPS to over OKC up to and beyond Missouri. There was; however; a break in the weather between SPS and LAW. We were on a South deviation between these two points at FL 410 when we experienced moderate to severe turbulence. Laterally we were well clear of the storms and encountered no precipitation. Moments after the turbulence began; the autopilot automatically disengaged and would not re-engage. I immediately began to hand fly the aircraft making constant power adjustments to maintain an appropriate airspeed which was rapidly fluctuating up and down due to the turbulence. Though I was initially flying the flight director the aircraft would not maintain altitude due to the turbulence. At this altitude; airspeed; and with the turbulence I was unwilling; for the sake of the safety of flight; to make hard and rapid pitch adjustments to try and reverse the descent. I did; however; hold a steady pitch and power setting that would under normal circumstance given me a climb. Before we were able to contact ATC and notify them of our inability to maintain altitude they contacted us and asked for our altitude; at this point were at approximately FL 395. The copilot responded that we were unable to maintain altitude and ATC cleared us to descend to FL350 and maintain present heading. ATC then asked why we were unable to maintain and I responded that we encountered moderate to severe turbulence and the aircraft was unable to hold altitude. Moments later the turbulence subsided. All of this occurred in approximately under a minute. Also during the turbulence the copilot was constantly calling out descent rates and airspeed. Max descent rate was approximately 2000 fpm and the airspeed fluctuated approximately 30 knots. Between my focus on hand flying the aircraft; my copilot's constant call outs and the busy radio communications due to the weather we were unable to contact ATC as soon as we would have liked to. I believe that the only way I could have maintained altitude would have been rapid and forceful control inputs. At this altitude and with the turbulence I believe this would have jeopardized the safety of flight and the structural integrity of the aircraft. If I was faced with this same scenario again; regardless of whether or the not the aircraft was maintaining altitude; I would immediately request a block altitude in the anticipation of the inability to maintain altitude.

Data retrieved from NASA's ASRS site as of April 2012 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.