Md-11 flight crew reported experiencing intermittent airspeed related malfunction alerts.

Attributes
ACN	1560608
Time
Date	201807
Local Time Of Day	1801-2400
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
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	Speed (Rate Sensing)
Person 1
Function	Pilot Flying Captain
Qualification	Flight Crew Instrument Flight Crew Multiengine Flight Crew Air Transport Pilot (ATP)
Person 2
Function	First Officer Pilot Not Flying
Qualification	Flight Crew Instrument Flight Crew Air Transport Pilot (ATP) Flight Crew Multiengine
Events
Anomaly	Aircraft Equipment Problem Critical

Narrative:

At FL350; M0.82; received flap disagree level 2 alert. The throttles then immediately went to idle thrust and the upper and lower foot on the ca (captain) pfd (primary flight display) came together. The flaps were indicating 0/ret on both the handle and the configuration page. Hydraulics were normal. All three airspeed indicators were indicating the same airspeed. All of these alerts were occurring intermittently but frequently and at a fast pace. Although I had disengaged the autothrottles to prevent them from going to idle; when the alerts occurred the autothrottles would re-engage as though the airplane was trying to go into high speed protection with no aural alerts. Because none of the checklists led us down the proper path; and we could not ascertain which pilot's side was the problem. We decided to return to ZZZ.we [advised ATC] and coordinated the return. The flight back was uneventful with the alerts occurring two more times. Things considered were the availability other airports enroute; the loss of a CADC (central air data computer) in rvsm airspace; and that it was a night oceanic flight. Maintenance is not sure. No faults were recorded. They did a precautionary replacement of CADC 1 and replaced FCC (flight control computer) 2.

Original NASA ASRS Text

Title: MD-11 flight crew reported experiencing intermittent airspeed related malfunction alerts.

Narrative: At FL350; M0.82; received Flap Disagree Level 2 Alert. The throttles then immediately went to idle thrust and the upper and lower foot on the CA (Captain) PFD (Primary Flight Display) came together. The flaps were indicating 0/ret on both the handle and the configuration page. Hydraulics were normal. All three airspeed indicators were indicating the same airspeed. All of these alerts were occurring intermittently but frequently and at a fast pace. Although I had disengaged the autothrottles to prevent them from going to idle; when the alerts occurred the autothrottles would re-engage as though the airplane was trying to go into High Speed Protection with no aural alerts. Because none of the checklists led us down the proper path; and we could not ascertain which pilot's side was the problem. We decided to return to ZZZ.We [advised ATC] and coordinated the return. The flight back was uneventful with the alerts occurring two more times. Things considered were the availability other airports enroute; the loss of a CADC (Central Air Data Computer) in RVSM airspace; and that it was a night oceanic flight. Maintenance is not sure. No faults were recorded. They did a precautionary replacement of CADC 1 and replaced FCC (Flight Control Computer) 2.

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.