Date: 201911
Local time of day: 1201-1800
Location: ZZZ.Airport, US
Flight conditions: IMC
Weather elements / visibility: Icing
Light: Night
Aircraft: Regional Jet 200 ER/LR (CRJ200)
Operator: Air Carrier
Operating under: Part 121
Flight plan: IFR
Mission: Passenger
Flight phase: Descent; Climb
Airspace: Class C ZZZ
ATC / advisory: TRACON ZZZ
Aircraft component: Flight Dynamics Navigation and Safety
Component problem: Malfunctioning; Failed
Reporter organization: Air Carrier
Reporter function: First Officer; Pilot Flying
Reporter qualification: Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine; Flight Crew Instrument
Human factors: Workload; Situational Awareness; Distraction; Confusion
Second reporter function: Pilot Not Flying; Captain
Anomaly: Aircraft Equipment Problem Critical; Deviation - Speed All Types; Deviation / Discrepancy - Procedural FAR; Inflight Event / Encounter Weather / Turbulence
Detector: Automation Aircraft Other Automation; Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Landed in Emergency Condition; Flight Crew FLC complied w / Automation / Advisory; Flight Crew Returned To Departure Airport
Contributing factors: Aircraft; Weather
Primary problem: Aircraft

Narrative: During climb phase of flight; while in IMC and Moderate Icing conditions; the FMA automatically switched from climb mode to IAS mode. No other indications of abnormalities; so I advised Captain; and pressed speed button on FCP (Flight Correction Proposal) (twice to return to climb mode at approximately 5;000 feet. FMA again showed IAS at approximately 7;000 feet; followed by amber-boxed ALT and amber-boxed IAS on both PFD's. PFD 2 speed tape was decreasing; and initially increased thrust to offset. Quickly realized PFD's were in dispute on airspeed. Altitude on PFD's also disagreed. Disengaged AP (Autopilot); cleared flight director and continued scanning instruments to verify which instruments unreliable. Requested Captain a climb out of IMC and Icing. Captain advised ATC of erratic air data; requested climb; and asked current altitude and speed. After repeated request; we were given 9000 feet; which was just above IMC layer. Discussed with Captain unreliable speed IAC and QRH. She noted previous training indicated an ADC failure instead so she ran ADC fail 2 QRH. During check list I advised icing was about an inch on windshield wipers and increasing; and my speed was dropping fast. Verified a 10 kts difference between standby and PFD1; however; PFD 1 Altitude showed much higher than PFD 2 and Standby and ATC advised altitude.From this; I was concerned to trust instruments; and due to icing on aircraft; opted to keep airspeed fast to protect from increased stall speeds until problem was verified. ATC was advised of problems and [Requested Priority Handling] with request to return to ZZZ. During the event; Captain acknowledged she could take the aircraft; but that I was doing fine maintaining and that she would continue working the issue. I maintained altitude at 9;000 feet off PFD2 and standby and speed was kept between 250-300 kts. while given delay vectors. After a quick setup and checklists; ATC gave a descent to 2;500 feet; followed by 2;000 feet. During descent; my instruments increased in error; and Captain advised speeds and altitudes. On break out of IMC; ice was shed and she took aircraft and we executed a stabilized approach and landing into ZZZ.Fatigue not a causal factor here. May have misunderstood what I was filling out on report. Was 100% fit for duty and fatigue was not an issue.I believe the event was handled properly based on safety as priority one. The question of which IAC or QRH to run regarding this event plays on previous recurrent training by Captain and the lack of specific indications relating to a QRH. It seemed to be a combination. In the process of initial reaction and verification of errors; the steps taken comprised the immediate actions required. On the one hand; the Unreliable Airspeed [Emergency Checklist] should be run; but is contrary to specific recurrent training received by the Captain. Regarding speed deviation; I could have maintained 250 kts. while below 10;000 feet and completely trusted PFD1 even though the altitude was unreliable; while possibly risking a slower than appropriate airspeed for icing conditions (which calls for increased speed) and questionable increased stall speeds. Considering all attributes; I believe the steps we took in priority order provided for the safest outcome. Due to the progressive nature of the failure; and increase in icing; returning to the nearest suitable airport as soon as possible was the best course of action.


Second narrative: ZZZ ATIS at departure time: 280 at 14 10 SM 5/-2 55 OVC. We were filed for 12;000 feet (above the cloud layer) but clearance said our final would be 8;000 feet. Prior to entering clouds; I turned on the cowl and wing anti ice. During the climb the FO's (First Officer) PFD displayed the yellow ALT icon (first; I think) and then yellow IAS icon shortly after. A bit later; my PFD followed; displaying the same icons. We were handed off to ZZZ1 Approach. I told ZZZ1 we were having air data issues and were not sure of our actual altitude or airspeed. I requested a climb out of icing conditions and asked for vectors so we could go work the problem. We climbed to 9;000 feet and were above the cloud layer there. Once level; I asked ZZZ1 what he was showing our altitude and airspeed to be. He said 9;000 feet and 300 kts. ground speed. By cross referencing our instruments; it appeared my altitude readout was erroneous because mine read 9;300 feet. The FO's was right at 9;000 feet. Our airspeeds did not match; but mine did match the standby airspeed. ZZZ1 came back to us and told us he was going to vector us back to ZZZ and handed us off to ZZZ Approach. As soon as I checked on I [Requested Priority Handling] and told ZZZ Approach what the problem was and requested a return for landing. The FO and I agreed he would continue to fly with reference to the standby airspeed and I would complete all the non-flying duties because it would be quicker; simply because of my experience of what needed to get done. ZZZ gave us a descent to 2;500 feet; back through icing conditions. During the descent it became obvious to us that we were dealing with a blocked pitot tube. I encouraged the FO to slow down because (even though we [Requested Priority Handling]) my airspeed consistently matched the standby. We were above 250 kts below 10;000 feet. I reiterated this to him all throughout the descent telling him my airspeed was matching the standby and to slow down. I took control of the aircraft once I had the runway in sight and performed a visual approach and landing.

Second callback: Captain was informed there was contamination found in the pitot/static line causing an ADC to fail.

Synopsis: CRJ-200 flight crew reported pitot tube was blocked with ice making airspeed unreliable.