Narrative:

[We experienced] severe clear air turbulence and wind shear; resulting loss of altitude and stick shaker; at FL390; in rather smooth air. I noticed the airspeed increasing and the autopilot not being aggressive enough to counter the issue. I pulled back the throttles a bit and almost instantly the airspeed jumped into the over-speed; accompanied by an increasing trend indication. I pulled the throttles all the way back to the flight-idle stop and the airspeed continued to increase. I had no choice but to kick off the autopilot and initiate a very slow rate of climb to counter the ever increasing airspeed. When I did so; even with the throttles at idle; the airspeed jumped into the over-speed indicator and we were climbing. We told the controller that we were unable to hold altitude due to a mountain wave-like; high altitude; and windshear condition. He said that there was 'no one above or below us' so traffic was not a threat. Our altitude got up to around FL395 as we fought the airspeed and; now accompanying moderate turbulence; this side of the event seemed to last about 60- 90 seconds. Being at FL390 already; I was concerned for the decreasing safe speed envelope as we were forced to climb; and did not want to pitch too much; knowing that we could get a decreasing performance shear and stall at a very high altitude. I was glad that I flew it that way; slightly into the barber pole (most of the time I didn't have much choice); because with throttles at flight idle; the only alternative to get out of the barber pole speed was excessive pitch and altitude and decreased airspeed envelope/safety margin. At the beginning of the event; we were instantaneously into the over-speed indicator; and probably reached an over-speed condition of plus 10 or 15 knots at times due to the turbulence.then; there seemed to be a transition period of maybe 5 seconds where I battled highly fluctuating airspeed indications/shear with pitch (while I tried to stay in the middle of the narrow airspeed envelope) and then I got the slow speed stick shaker and yellow stall pitch indicator. We believe that we lost 60 to 70 knots of airspeed in the snap of a finger. I lowered the nose smoothly and appropriately and jammed the power in full; but not through the over-speed bar. Interestingly; the performance decrease was so great that it seemed I had not added power at all. The airspeed was not increasing as you might expect; and there was no sensation; no feel in 'the seat of your pants' as you get with extra thrust. The engines were operating normally; but their performance was no match for the wind shear. We lost at least 1;000 feet before we were able to get the airspeed to increase commensurate with engine power and pitch. Now that we were safely lower and still in turbulence; we got a lower altitude assignment from the controller. An rj aircraft behind us had a similar experience minutes after us. We took notes as much as possible on the event; selected the 'event marker' button on the instrument panel; notified ATC; company dispatch and company maintenance via satcom. I have had my share of tense moments in my career; but this one stands out as one of the most perilous.the weather and aircraft appeared; on the surface; to perform very similar to a low-level wind shear; like the ones we train for repeatedly in the simulator. The airspeed fluctuations and resulting turbulence were similar; but the added effect of high-altitude operations was very different. That was a 'curve ball' of extra issues to contemplate and mesh with what I had seen in the simulator during LLWS [low level wind shear] training. Given the safe result of the flight and the captain's positive feedback; I am confident that I flew the profile to the best of my abilities. However; I don't recall ever seeing a high-altitude wind shear event in the simulator (maybe a mach-tuck demo once) and; therefore; I am curious whether I could have done anything better. I would love to see something like this in a training simulator profile at some point; or even see the re-creation of my flight instruments during the actual event; as might be possible through the fdr event marker. I believe this was a dire situation and could have had a much less successful outcome; so I would really prefer to see this again in the training world; before I see it again in the real world.

Google
 

Original NASA ASRS Text

Title: An MD11 First Officer related a harrowing wind shear encounter with large altitude deviations and both high and low airspeed warnings.

Narrative: [We experienced] severe Clear Air Turbulence and Wind Shear; resulting loss of altitude and stick shaker; at FL390; in rather smooth air. I noticed the airspeed increasing and the autopilot not being aggressive enough to counter the issue. I pulled back the throttles a bit and almost instantly the airspeed jumped into the over-speed; accompanied by an increasing trend indication. I pulled the throttles all the way back to the flight-idle stop and the airspeed continued to increase. I had no choice but to kick off the autopilot and initiate a very slow rate of climb to counter the ever increasing airspeed. When I did so; even with the throttles at idle; the airspeed jumped into the over-speed indicator and we were climbing. We told the Controller that we were unable to hold altitude due to a mountain wave-like; high altitude; and windshear condition. He said that there was 'no one above or below us' so traffic was not a threat. Our altitude got up to around FL395 as we fought the airspeed and; now accompanying moderate turbulence; this side of the event seemed to last about 60- 90 seconds. Being at FL390 already; I was concerned for the decreasing safe speed envelope as we were forced to climb; and did not want to pitch too much; knowing that we could get a decreasing performance shear and stall at a very high altitude. I was glad that I flew it that way; slightly into the barber pole (most of the time I didn't have much choice); because with throttles at flight idle; the only alternative to get out of the barber pole speed was excessive pitch and altitude and decreased airspeed envelope/safety margin. At the beginning of the event; we were instantaneously into the over-speed indicator; and probably reached an over-speed condition of plus 10 or 15 knots at times due to the turbulence.Then; there seemed to be a transition period of maybe 5 seconds where I battled highly fluctuating airspeed indications/shear with pitch (while I tried to stay in the middle of the narrow airspeed envelope) and then I got the slow speed stick shaker and yellow stall pitch indicator. We believe that we lost 60 to 70 knots of airspeed in the snap of a finger. I lowered the nose smoothly and appropriately and jammed the power in full; but not through the over-speed bar. Interestingly; the performance decrease was so great that it seemed I had not added power at all. The airspeed was not increasing as you might expect; and there was no sensation; no feel in 'the seat of your pants' as you get with extra thrust. The engines were operating normally; but their performance was no match for the wind shear. We lost at least 1;000 feet before we were able to get the airspeed to increase commensurate with engine power and pitch. Now that we were safely lower and still in turbulence; we got a lower altitude assignment from the Controller. An RJ aircraft behind us had a similar experience minutes after us. We took notes as much as possible on the event; selected the 'event marker' button on the instrument panel; notified ATC; Company Dispatch and Company Maintenance via Satcom. I have had my share of tense moments in my career; but this one stands out as one of the most perilous.The weather and aircraft appeared; on the surface; to perform very similar to a low-level wind shear; like the ones we train for repeatedly in the simulator. The airspeed fluctuations and resulting turbulence were similar; but the added effect of high-altitude operations was very different. That was a 'curve ball' of extra issues to contemplate and mesh with what I had seen in the simulator during LLWS [Low Level Wind Shear] training. Given the safe result of the flight and the Captain's positive feedback; I am confident that I flew the profile to the best of my abilities. However; I don't recall ever seeing a high-altitude wind shear event in the simulator (maybe a mach-tuck demo once) and; therefore; I am curious whether I could have done anything better. I would LOVE to see something like this in a training simulator profile at some point; or even see the re-creation of my flight instruments during the actual event; as might be possible through the FDR event marker. I believe this was a dire situation and could have had a much less successful outcome; so I would really prefer to see this again in the training world; before I see it again in the real world.

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.