Narrative:

First officer was hand flying while climbing off of runway xxr on the SID while departing ZZZZ. I noticed the airspeed decreasing while the airplane was increasing pitch. This was prior to flap retraction; so it was less than 3;000 ft. I verbalized to the first officer 'watch your airspeed.' when I said this; the first officer looked at his indicated airspeed and then at mine; while I was doing the same. We realized that one of the airspeed indicators was incorrect. We were able to determine that it was most likely the first officer's airspeed that was incorrect based on the standby altimeter and airspeed indicator that was matching mine. I took control of the airplane and was hand flying the airplane while the first officer pulled out the QRH. We also started receiving multiple level-two alerts and noticed the autopilot and auto throttles were inoperative. The flight director failed [and] the fcp (flight control panel) had dashed lines in the windows. During the climb the first officer was converting meters to feet to be used. The fcp was not working at all. Airspeed; heading; altitude; and climbs were all determined and complied with without automation. No airspeed bugs; no altitude bugs; no heading bugs were usable. I tried to fly the departure via the magenta navigation line while constantly increasing/decreasing the map range to ensure terrain and aircraft separation.while we were trying to sort through the alerts to determine what checklist to perform we continued to climb when instructed up to 2;100 meters and finally 6;300 meters. Sometime early in the climb; the CAWS (caution and warning system) 'overspeed' was annunciating due to the first officer's false airspeed. It was indicating it was exceeding the top foot. We realized that the proper checklist was the airspeed unreliable checklist. The CAWS 'overspeed' call lasted throughout the event making it extremely difficult to communicate with ZZZZ and the complete the checklist. The language barrier with the controllers was equally challenging.in the climb we were also asked to speed up for traffic flow. While we were sorting out the problem I attempted to keep the airspeed around 280 kts to ensure we weren't exceeding any limitations; but giving us enough airspeed for performance. Shortly after this request as I leveled at 20;700 ft. (6;300 meters); we were queried about our altitude. My altimeter was indicating 20;700 ft. And my first officer's altimeter was 1;000 ft. Above and the controller said we were showing 300 meters high. This was close to the time we were able to [advise ATC]. We [requested priority handling] to return back to ZZZZ. We were issued a left turn to 090 and started our descent. We were vectored back to runway xxr and landed uneventfully.the language challenges; dealing with the constant 'overspeed' CAWS; multiple alerts in conjunction with a lack of automation made this event extremely challenging.when we were debriefing the event after blocking in; we determined the altitude deviation was due to the #2 transponder being selected but indicating [inaccurate] information. The first officer did a great job managing the radios and performing the checklists. Maintenance at ZZZZ found an air data computer #2 fault.

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Original NASA ASRS Text

Title: MD-11 flight crew reported Air Data Computer malfunction resulted in multiple instrumentation and system failures during climbout and required a return to land.

Narrative: First Officer was hand flying while climbing off of Runway XXR on the SID while departing ZZZZ. I noticed the airspeed decreasing while the airplane was increasing pitch. This was prior to flap retraction; so it was less than 3;000 ft. I verbalized to the First Officer 'watch your airspeed.' When I said this; the First Officer looked at his Indicated Airspeed and then at mine; while I was doing the same. We realized that one of the airspeed indicators was incorrect. We were able to determine that it was most likely the First Officer's airspeed that was incorrect based on the standby altimeter and airspeed indicator that was matching mine. I took control of the airplane and was hand flying the airplane while the First Officer pulled out the QRH. We also started receiving multiple level-two alerts and noticed the autopilot and auto throttles were inoperative. The Flight Director failed [and] the FCP (Flight Control Panel) had dashed lines in the windows. During the climb the First Officer was converting meters to feet to be used. The FCP was not working at all. Airspeed; heading; altitude; and climbs were all determined and complied with without automation. No airspeed bugs; no altitude bugs; no heading bugs were usable. I tried to fly the departure via the magenta navigation line while constantly increasing/decreasing the map range to ensure terrain and aircraft separation.While we were trying to sort through the alerts to determine what checklist to perform we continued to climb when instructed up to 2;100 meters and finally 6;300 meters. Sometime early in the climb; The CAWS (Caution and Warning System) 'overspeed' was annunciating due to the First Officer's false airspeed. It was indicating it was exceeding the top foot. We realized that the proper checklist was the Airspeed Unreliable checklist. The CAWS 'overspeed' call lasted throughout the event making it extremely difficult to communicate with ZZZZ and the complete the checklist. The language barrier with the Controllers was equally challenging.In the climb we were also asked to speed up for traffic flow. While we were sorting out the problem I attempted to keep the airspeed around 280 kts to ensure we weren't exceeding any limitations; but giving us enough airspeed for performance. Shortly after this request as I leveled at 20;700 ft. (6;300 meters); we were queried about our altitude. My altimeter was indicating 20;700 ft. and my First Officer's altimeter was 1;000 ft. above and the Controller said we were showing 300 meters high. This was close to the time we were able to [advise ATC]. We [requested priority handling] to return back to ZZZZ. We were issued a left turn to 090 and started our descent. We were vectored back to Runway XXR and landed uneventfully.The language challenges; dealing with the constant 'overspeed' CAWS; multiple alerts in conjunction with a lack of automation made this event extremely challenging.When we were debriefing the event after blocking in; we determined the altitude deviation was due to the #2 transponder being selected but indicating [inaccurate] information. The First Officer did a great job managing the radios and performing the checklists. Maintenance at ZZZZ found an ADC #2 fault.

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.