Md-11 flight crew reported failure of central air data computer at cruise in IMC conditions.

Narrative:

Airspeed decay at FL380; engine and wing anti ice on. Shortly after that numerous alerts (level 2 sel elev feel man; level 2 flap lim ovrd; level 2 sel fadec altitude) [displayed]. Both pfds (primary flight display) showed the IAS comparator light. Referenced the standby a/south (airspeed) indicator. Autopilot and autothrottles disconnected on their own and not available. Asked for an immediate descent to FL340 and a left turn to avoid weather 40nm on our nose. I continued to fly the a/C (aircraft) using raw data while the first officer (first officer) consulted the QRH. First officer's a/south indicator showed 40 knots slower than the standby indicator and the captain's side. His was in the lower foot and mine was at the top of the lower foot. I assigned one cockpit jumpseater to take over the number 1 radio and coordinate weather avoidance and tasked the 2nd cockpit jumpseater to go in the back and ask the jumpseating captain sitting in the back to return to the cockpit (ex md-11 guy). First officer ran the QRH which lead to the erratic a/south checklist. After running that checklist; it was determined that the number 2 CADC (central air data computer) had failed. During this evert; our radios [had a lot of] static and hard to understand. We thought we were given a frequency change and were on the wrong frequency for about a minute or two. First officer and jumpseaters did an outstanding job of backing us up during a very demanding and task saturated event.

Original NASA ASRS Text

Title: MD-11 flight crew reported failure of Central Air Data Computer at cruise in IMC conditions.

Narrative: Airspeed decay at FL380; engine and wing anti ice on. Shortly after that numerous alerts (Level 2 SEL ELEV FEEL MAN; Level 2 FLAP LIM OVRD; Level 2 SEL FADEC ALT) [displayed]. Both PFDs (Primary Flight Display) showed the IAS comparator light. Referenced the standby A/S (Airspeed) indicator. Autopilot and autothrottles disconnected on their own and not available. Asked for an immediate descent to FL340 and a left turn to avoid weather 40nm on our nose. I continued to fly the A/C (aircraft) using raw data while the FO (First Officer) consulted the QRH. FO's A/S indicator showed 40 knots slower than the standby indicator and the Captain's side. His was in the lower foot and mine was at the top of the lower foot. I assigned one cockpit jumpseater to take over the Number 1 radio and coordinate weather avoidance and tasked the 2nd cockpit jumpseater to go in the back and ask the jumpseating Captain sitting in the back to return to the cockpit (ex MD-11 guy). FO ran the QRH which lead to the erratic A/S checklist. After running that checklist; it was determined that the Number 2 CADC (Central Air Data Computer) had failed. During this evert; our radios [had a lot of] static and hard to understand. We thought we were given a frequency change and were on the wrong frequency for about a minute or two. FO and jumpseaters did an outstanding job of backing us up during a very demanding and task saturated 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	1534402
Time
Date	201804
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	IMC
Light	Daylight
Aircraft 1
Make Model Name	MD-11
Operating Under FAR Part	Part 121
Flight Phase	Cruise
Flight Plan	IFR
Person 1
Function	Captain Pilot Flying
Qualification	Flight Crew Air Transport Pilot (ATP) Flight Crew Instrument Flight Crew Multiengine
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Multiengine Flight Crew Instrument Flight Crew Air Transport Pilot (ATP)
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Speed All Types Inflight Event / Encounter Weather / Turbulence