Flight Crew Air Transport Pilot (ATP)
Aircraft Equipment Problem Less Severe; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Flight Crew Overcame Equipment Problem; Flight Crew Took Evasive Action
Weather; Aircraft
Flying at FL200 in IMC with light to moderate icing; we had both the cowl and wing anti-ice on. [We then received] the warning message ANTI ICE DUCT. I instructed the FO who was PF at the time to also take the radios while I ran the QRH. It instructed us to shut off the wing anti-ice and leave icing conditions. I shut off the wing anti-ice which cleared the message. I radioed Center that we needed an immediate climb. The controller was busy and did not respond right away to my call. When they did respond; they gave us a climb and inquired if we needed assistance. I told them we would keep them advised and that we were having trouble with our anti-ice system. Once above the clouds; we were able to determine ice had formed on the wings. Therefore we continued with the ice dispersal procedure as directed by the QRH. While waiting for the ice to dissipate; I requested from ATC that they not descend us until they could give us an unrestricted descent to 7;000 (an altitude I had calculated to be above freezing using the surface temperature in ZZZ of 14 degrees and standard lapse rate of 2 degrees per 1000 ft.). The controller was cooperative and passed along our request to Approach. Center asked us to slow and gave us pilot discretion on a descent. I informed ATC we still had ice on our wings and would not be able to slow. The controller then told us to maintain slowest practical airspeed. At this point; I informed ATC. My reasoning was that we still had ice on the wings that appeared to not be dissipating; and it would not be safe to slow the airplane with ice on the wings. While surface temperatures were well above freezing; IMC was prevailing across the region and we were going to need to descend back through icing conditions to land the airplane. Therefore I needed to be able to descend quickly through the clouds to reach warmer air and be able to maintain high airspeeds until there was no longer a threat of ice.ATC vectored us off the arrival and gave us the descent to 7000 when terrain allowed. Dispatch was notified via ACARS of our status. The ice was not dissipating off the wings with the QRH procedure of using high airspeed. Therefore I continued on with the next step in the QRH which instructed me to turn the wing anti-ice back on; but also to shut it off immediately when the warning message returned. With the wing anti-ice on; the ice melted from the wings. However; the warning message did not return. Once we reached 7000 feet and verified both the SAT and TAT were well above freezing I informed ATC. The flight continued through landing without further incident.
CRJ-700 Captain reported they lost anti-ice capability in light to moderate icing after responding to the message ANTI ICE DUCT. They exited icing conditions and were able to restore the anti-ice system later in flight.