MD11 flight crew encountered extreme turbulence in cruise.

Narrative:

At approximately 100 miles west of zzzzz at FL310 ZZZZ radio descended us to FL300 due to traffic. At approximately 50 miles west of zzzzz we encountered extreme wind shear with gains/losses of 25-30kts and gains/losses of 500 feet in altitude. The winds were about 270/125. The autopilot disconnected twice with multiple stick shaker activations; (3 or 4 times); accompanied with tail-wind shear alert displayed on captains pfd (primary flight display). At one point the airspeed was 5kts about the foot with maximum power selected and we were still unable to maintain altitude. I advised that we were unable to maintain our altitude and that we were descending and requested a block altitude of FL270-280. This was approved by ZZZZ radio. The aircraft was under control and able to maintain altitude at FL280 with the spot winds of 270/65 in continuous moderate turbulence. This lasted for about another 5-10 minutes. We remained at FL280 until climbing at ZZZZZ1 to FL310 and talking to ZZZ radio. The first officer did a very good job of controlling the 'attitude' of the aircraft throughout the entire event.

Original NASA ASRS Text

Title: MD11 flight crew encountered extreme turbulence in cruise.

Narrative: At approximately 100 miles West of ZZZZZ at FL310 ZZZZ Radio descended us to FL300 due to traffic. At approximately 50 miles West of ZZZZZ we encountered extreme wind shear with gains/losses of 25-30kts and gains/losses of 500 feet in altitude. The winds were about 270/125. The autopilot disconnected twice with multiple stick shaker activations; (3 or 4 times); accompanied with tail-wind shear alert displayed on Captains PFD (Primary Flight Display). At one point the airspeed was 5kts about the foot with MAX Power selected and we were still unable to maintain altitude. I advised that we were unable to maintain our altitude and that we were descending and requested a block altitude of FL270-280. This was approved by ZZZZ Radio. The aircraft was under control and able to maintain altitude at FL280 with the spot winds of 270/65 in continuous moderate turbulence. This lasted for about another 5-10 minutes. We remained at FL280 until climbing at ZZZZZ1 to FL310 and talking to ZZZ Radio. The First Officer did a very good job of controlling the 'attitude' of the aircraft throughout the entire event.

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	1743803
Time
Date	202005
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZ.ARTCC
State Reference	FO
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	MD-11
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Route In Use	Oceanic
Flight Plan	IFR
Person 1
Function	Captain Pilot Not Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Person 2
Function	Pilot Flying First Officer
Qualification	Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Deviation - Altitude Excursion From Assigned Altitude Deviation - Procedural Clearance Inflight Event / Encounter Weather / Turbulence