Center controller reported a helicopter descended through minimum IFR altitude due to icing.

Attributes
ACN	1766784
Time
Date	202010
Local Time Of Day	1201-1800
Place
Locale Reference	ZZZ.ARTCC
State Reference	US
Environment
Flight Conditions	IMC
Aircraft 1
Make Model Name	S-70/UH-60 Blackhawk/Seahawk/Pavehawk/Knighthawk
Operating Under FAR Part	Part 91
Flight Phase	Cruise
Flight Plan	IFR
Component
Aircraft Component	Ice/Rain Protection System
Person 1
Function	Enroute
Qualification	Air Traffic Control Fully Certified
Events
Anomaly	Aircraft Equipment Problem Critical Deviation - Altitude Overshoot Deviation - Procedural Clearance Inflight Event / Encounter Weather / Turbulence Inflight Event / Encounter Loss Of Aircraft Control Inflight Event / Encounter Fuel Issue

Narrative:

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.

Original NASA ASRS Text

Title: Center Controller reported a helicopter descended through minimum IFR altitude due to icing.

Narrative: 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.

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.