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 altitude 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 air data computer failure instead so she ran air data computer 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.

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Original NASA ASRS Text

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

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.

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.