S-70/UH-60 Blackhawk/Seahawk/Pavehawk/Knighthawk
Air Traffic Control Fully Certified
Aircraft Equipment Problem Critical; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Fuel Issue; Inflight Event / Encounter Loss Of Aircraft Control; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Air Traffic Control Provided Assistance; Flight Crew Diverted
Airspace Structure; Weather; Aircraft
Aircraft X departed originally VFR under IFR conditions. TRACON was able to give IFR clearance. Aircraft X was level at 5000 ft. Upon entrance into the sector; they encountered icing conditions. Aircraft X was [issued a] climb to 8000 ft. and got out of the icing. Enroute to original destination; pilot asked for a diversion to ZZZ airport due to fuel. I cleared and gave aircraft pilot's discretion clearance to 5000 ft. That put aircraft back into icing conditions of which then icing equipment malfunctioned. Pilot asked for a descent out of the icing conditions. I issued a descent to 4900 ft. which was the lowest MIA (Minimum IFR Altitude). Pilot took the descent but continued to descend. Pilot was not able to maintain altitude and continued descending. We were looking for a safe place for the helicopter to land. Also; wanted to keep aircraft out of the clouds due to icing. Aircraft X requested priority handling. I tried to assist the best way I could due to the conditions. Pilot reported being in moderate to heavy icing conditions and was unable to maintain altitude.
Center Controller reported a helicopter descended through minimum IFR altitude due to icing.