Citation II S2/Bravo (C550)
Flight Crew Instrument; Flight Crew Multiengine; Flight Crew Air Transport Pilot (ATP)
Flight Crew Last 90 Days 120; Flight Crew Total 13500; Flight Crew Type 2500
Situational Awareness; Distraction; Workload
Aircraft Equipment Problem Less Severe; Deviation - Altitude Overshoot; Deviation / Discrepancy - Procedural Clearance; Deviation / Discrepancy - Procedural Published Material / Policy; Inflight Event / Encounter Weather / Turbulence
Air Traffic Control Issued New Clearance; Flight Crew Became Reoriented; Flight Crew Returned To Clearance
Aircraft; Human Factors; Weather
While on descent out of FL250 it was reported there was light rime ice just about 50 miles NW of ZZZ. I acknowledged. About 2 minutes later we entered the clouds and I turned my anti ice systems on. I then began picking up ice. My left engine ice failed and I immediately asked for lower stating that I was having device systems issues. Center descended me immediately to FL210. Once I started the descent I began reading checklists and working the system. I then noticed the autopilot altitude select didn't arm and I descended below my assigned altitude. Once I realized it I was starting back up but Center just cleared me to 13;000 feet. They never said anything to me and there wasn't another aircraft in the area. No deviations or conflicts. The main issue was dealing with the deice problem while getting ice in the descent. I was descending at 2500 ft min to get below the ice which was around 19;500 feet.
CE550 Captain reported overshooting a cleared altitude while descending in icing conditions with a failure of the left engine anti-ice system.