A md-11 encountered moderate to severe turbulence in light cirrus clouds and with a low speed stall ...

Narrative:

We were deviating right of course (to the west of course) to avoid a thunderstorm that [was] shown on our radar. We entered a layer of high cirrus clouds and were IMC with light precipitation (patchy green return) showing on our radar. With the autopilot engaged we encountered moderate to severe turbulence when suddenly the airspeed became uncontrollable and the aircraft entered the low speed stick shaker. I disconnected the autopilot and lowered the nose in an attempt to regain airspeed. The aircraft remained in the low speed stick shaker for 10-20 seconds as we attempted recovery. When sufficient airspeed was regained we made a controlled climb back to assigned altitude. The total altitude loss was approximately 700 feet. ATC was notified of the altitude deviation and the circumstances involved at that time. ATC told us that they had noticed the altitude deviation; that there were no other aircraft in the vicinity; and there was no loss of separation. This was an inadvertent encounter with severe turbulence/thunderstorm that did not show on the radar.

Original NASA ASRS Text

Title: A MD-11 encountered moderate to severe turbulence in light cirrus clouds and with a low speed stall warning descended 700 feet then returned to their cleared altitude. ATC was notified.

Narrative: We were deviating right of course (to the west of course) to avoid a thunderstorm that [was] shown on our radar. We entered a layer of high cirrus clouds and were IMC with light precipitation (patchy green return) showing on our radar. With the autopilot engaged we encountered moderate to severe turbulence when suddenly the airspeed became uncontrollable and the aircraft entered the low speed stick shaker. I disconnected the autopilot and lowered the nose in an attempt to regain airspeed. The aircraft remained in the low speed stick shaker for 10-20 seconds as we attempted recovery. When sufficient airspeed was regained we made a controlled climb back to assigned altitude. The total altitude loss was approximately 700 feet. ATC was notified of the altitude deviation and the circumstances involved at that time. ATC told us that they had noticed the altitude deviation; that there were no other aircraft in the vicinity; and there was no loss of separation. This was an inadvertent encounter with severe turbulence/thunderstorm that did not show on the radar.

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.

Attributes
ACN	1176060
Time
Date	201405
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	MD-11
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Inflight Event / Encounter Loss Of Aircraft Control Inflight Event / Encounter Weather / Turbulence

A md-11 encountered moderate to severe turbulence in light cirrus clouds and with a low speed stall warning descended 700 feet then returned to their cleared altitude. ATC was notified.