MD11 flight crew experiences dual air data computer failures at FL360. Stall warnings are activated ...

Narrative:

Stick shaker occurred; but both primary flight displays initially showed normal airspeed. During the next several minutes; various alerts/warnings and conflicting data continued. Following the stick shaker onset; and during the time needed to process and interpret the instruments; I witnesses what I perceived as a stall buffet. I immediately added maximum power then lowered pitch. Stall indications continued during descent with considerable altitude loss. Captain could neither verify/interpret the instruments initially; and was concerned about my altitude deviation as radio congestion and primary efforts of 'aviating' prevented the prompt declaration of our emergency or setting of the appropriate transponder code. The multiple distractions of alerts and conflicting instruments led to considerable confusion; and I found it extremely difficult to follow the standby instruments to recovery efficiently. With this scenario and the captain's desire to return to altitude; I allowed a secondary stick shaker/stall buffet. The other crewmembers were summoned forward to assist and to complete appropriate checklists; and the captain assumed flying pilot duties at some point after stall recovery was complete and while I was attempting stabilized flight via reference to the standby instruments. We felt strongly that it was not a simple failure of one air data computer; and that all the symptoms did not result from an air data computer failure as we had experienced in training. The captain and I both feel it is imperative to require crew training in high speed stall situations by use of only standby instruments; to include distractions attendant with erroneous presentations and the various alerts both aural and displayed. As the captain is the check airman; he has already received assurances that such training is to be placed in the company program.

Original NASA ASRS Text

Title: MD11 flight crew experiences dual ADC failures at FL360. Stall warnings are activated and altitude is lost as the First Officer recovers using standby instruments. Many of the problems clear up at low altitude and flight continues to destination after declaring an emergency.

Narrative: Stick shaker occurred; but both primary flight displays initially showed normal airspeed. During the next several minutes; various alerts/warnings and conflicting data continued. Following the stick shaker onset; and during the time needed to process and interpret the instruments; I witnesses what I perceived as a stall buffet. I immediately added maximum power then lowered pitch. Stall indications continued during descent with considerable altitude loss. Captain could neither verify/interpret the instruments initially; and was concerned about my altitude deviation as radio congestion and primary efforts of 'aviating' prevented the prompt declaration of our emergency or setting of the appropriate transponder code. The multiple distractions of alerts and conflicting instruments led to considerable confusion; and I found it extremely difficult to follow the standby instruments to recovery efficiently. With this scenario and the Captain's desire to return to altitude; I allowed a secondary stick shaker/stall buffet. The other crewmembers were summoned forward to assist and to complete appropriate checklists; and the Captain assumed flying pilot duties at some point after stall recovery was complete and while I was attempting stabilized flight via reference to the standby instruments. We felt strongly that it was not a simple failure of one Air Data Computer; and that all the symptoms did not result from an ADC failure as we had experienced in training. The Captain and I both feel it is imperative to require crew training in high speed stall situations by use of only standby instruments; to include distractions attendant with erroneous presentations and the various alerts both aural and displayed. As the Captain is the check airman; he has already received assurances that such training is to be placed in the company program.

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.

Attributes
ACN	893287
Time
Date	201006
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZZ.ARTCC
State Reference	FO
Environment
Flight Conditions	VMC
Light	Night
Aircraft 1
Make Model Name	MD-11
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Air Data Computer
Person 1
Function	First Officer Relief Pilot Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 49 Flight Crew Total 10000 Flight Crew Type 2226
Person 2
Function	Pilot Not Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 100 Flight Crew Total 12500 Flight Crew Type 7000
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Altitude Excursion From Assigned Altitude Deviation - Speed All Types Inflight Event / Encounter Loss Of Aircraft Control

MD11 flight crew experiences dual air data computer failures at FL360. Stall warnings are activated and altitude is lost as the first officer recovers using standby instruments. Many of the problems clear up at low altitude and flight continues to destination after declaring an emergency.