Md-11 flight crew reported erroneous and conflicting airspeed and vertical speed indications between...

Attributes
ACN	1513177
Time
Date	201801
Local Time Of Day	0601-1200
Place
Locale Reference	ZZZZ.Airport
State Reference	FO
Environment
Flight Conditions	VMC
Light	Daylight
Aircraft 1
Make Model Name	MD-11
Operating Under FAR Part	Part 121
Flight Phase	Takeoff
Flight Plan	IFR
Component
Aircraft Component	Air Data Computer
Person 1
Function	Pilot Not Flying Captain
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 250 Flight Crew Total 11500 Flight Crew Type 5000
Person 2
Function	Pilot Not Flying Relief Pilot
Qualification	Flight Crew Air Transport Pilot (ATP)
Experience	Flight Crew Last 90 Days 145 Flight Crew Total 4800 Flight Crew Type 433
Events
Anomaly	Aircraft Equipment Problem Less Severe

Narrative:

During takeoff at approximately 110 knots an erroneous airspeed indication was noticed. The first officer (first officer) and stby airspeed indicators appeared correct and cpt (captain) airspeed was degrading. The decision to continue the to (takeoff) was made and on climbout; cpt airspeed tape went blank and first officer vsi was erroneous. Using system knowledge; cpt CADC (central air data computer) was placed to 2 in order to receive airspeed info from first officer source. What followed was a plethora of degradations and erroneous indications of airspeed; vertical speed and autopilot anomalies. On AP2 the first officer was unable to capture an altitude or maintain a selected vs. On AP1 there were differences in as of up to 20kts. When the CADC was switched back to 1 on cpt side; the speed tape disappeared and the cpt vsi indicated a rapid descent. Because there was no determining reason why this was happening; no chain of events that could pinpoint the source of the failure and there was also no way to maintain a consistent flight path devoid of erroneous information the decision was made to return to ZZZZ. Our very helpful dispatcher; asked if we would consider diverting to ZZZZ1. Clearly this would have been a good option; but I felt that the airplane had too many unexplained issues and a further degradation would have not been good.

Original NASA ASRS Text

Title: MD-11 flight crew reported erroneous and conflicting airspeed and vertical speed indications between the Captain's and First Officer's flight displays.

Narrative: During takeoff at approximately 110 knots an erroneous airspeed indication was noticed. The FO (First Officer) and STBY airspeed indicators appeared correct and CPT (Captain) airspeed was degrading. The decision to continue the TO (Takeoff) was made and on climbout; CPT airspeed tape went blank and FO VSI was erroneous. Using system knowledge; CPT CADC (Central Air Data Computer) was placed to 2 in order to receive airspeed info from FO source. What followed was a plethora of degradations and erroneous indications of airspeed; vertical speed and autopilot anomalies. On AP2 the FO was unable to capture an altitude or maintain a selected VS. On AP1 there were differences in AS of up to 20kts. When the CADC was switched back to 1 on CPT side; the speed tape disappeared and the CPT VSI indicated a rapid descent. Because there was no determining reason why this was happening; no chain of events that could pinpoint the source of the failure and there was also no way to maintain a consistent flight path devoid of erroneous information the decision was made to return to ZZZZ. Our very helpful Dispatcher; asked if we would consider diverting to ZZZZ1. Clearly this would have been a good option; but I felt that the airplane had too many unexplained issues and a further degradation would have not been good.

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.

Md-11 flight crew reported erroneous and conflicting airspeed and vertical speed indications between the captain's and first officer's flight displays.