Date: 202101
Local time of day: 0601-1200
Location: SCT.TRACON, CA
Flight conditions: IMC
Weather elements / visibility: Cloudy; Icing; Rain; Turbulence
Light: Daylight
Aircraft: MD-11
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Cargo / Freight / Delivery
Flight phase: Climb; Parked
ATC / advisory: TRACON SCT
Aircraft component: Autopilot
Component problem: Malfunctioning
Reporter organization: Air Carrier
Reporter function: Captain; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Instrument; Flight Crew Multiengine
Second reporter function: Pilot Not Flying
Anomaly: Aircraft Equipment Problem Critical; Deviation - Altitude Excursion From Assigned Altitude; Deviation - Speed All Types; Deviation / Discrepancy - Procedural Maintenance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Flight Crew Regained Aircraft Control; Flight Crew Overcame Equipment Problem; General Maintenance Action; General Flight Cancelled / Delayed
Contributing factors: Aircraft; Procedure
Primary problem: Procedure

Narrative: During moderate turbulence and deviation around weather; airspeed became wildly erratic. Between maximum and minimum; the autopilot disconnected and several Level Two alerts displayed. I called; 'Airspeed unreliable;' disconnected AFS Override and Flight Director Switches; and established pitch for aircraft stabilized flight. The First Officer's airspeed was the closest to the Standby Instruments; and transfer of control was given to the FO (First Officer). Level Two 'SEL FADEC 1;2 3 ALTN'; 'SEL FLAP LIM OVRD' and 'SEL ELV FEEL MAN' were displayed. The QRH procedures were completed and the flight continued without incident. Possible CADC #1 failure or pitot static malfunction. [Responded as] described above. Additionally; inspection of the logbook revealed that related malfunctions had occurred [previously on four separate dates]. This would suggest that the problem is ongoing and requires further action. [I suggest] maintenance troubleshooting of all related issues by reference to all previous write-ups.


Second narrative: Airspeed unreliable event. Possible altitude deviation. I was deadheading on flight sitting in the observer seat. There were thunderstorms in vicinity and we were experiencing light to moderate rain and turbulence. CA (Captain) was PF (Pilot Flying) with autopilot engaged in climb to 14;000 MSL and also communicating to ATC on Com 1. FO (First Officer) was speaking to Operations on Com 2. I'm not sure exactly what altitude event occurred but happened around 14;000 MSL. There was a high speed warning and I noticed a large difference in airspeed between the CA and FO side. The CA-side airspeed was declining rapidly while FO-side was overspeeding slightly. The Captain recognized the issue and performed the memory items correctly and stabilized the aircraft. It was determined the FO-side was correct and the aircraft control was transferred to FO. The QRH was performed and CADC 2 was selected. There was no further incident. After the event we discussed the possibility of an altitude deviation during the recovery. There was a level off and delayed climb. I did not have a headset on and could not hear any altitude clearances or ATC communication. ATC did not inform the crew of any deviation. The crew handled the emergency well.[Responded by having an] in-depth discussion among the crew about the event and how to handle it better. Reports. Captain discussed event with Maintenance and entered it into logbook. In our event debrief it was discovered that this event has happened multiple times in this aircraft. The FO and another Deadheader both had separate airspeed unreliable events in the same aircraft in similar meteorological conditions. We read through the logbook to discover that this has happened multiple times recently and the aircraft has continued to be put back into service with no permanent resolution. The principle recommendation would be to correctly resolve the issue that is causing this. As for my part in this event; I realized I could have been more active in listening if I were using a headset. I could have verified the ATC clearance and assisted in communication.


Synopsis: MD-11 flight crew reported turbulence and an airspeed disparity between the instruments disconnected the autopilot and resulted in a possible altitude deviation.