Date: 201911
Local time of day: 0601-1200
Location: ZZZ.Airport, US
Weather elements / visibility: Icing; 1
Aircraft: Skyhawk 172/Cutlass 172
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Ferry / Re-Positioning
Flight phase: Cruise
Airspace: Class E ZZZ
Reporter organization: Personal
Reporter function: Pilot Flying
Reporter qualification: Flight Crew Commercial; Flight Crew Flight Instructor
Human factors: Workload
Anomaly: Deviation / Discrepancy - Procedural Clearance; Inflight Event / Encounter Weather / Turbulence
Detector: Person Flight Crew
When detected: In-flight
Result: Air Traffic Control Provided Assistance; Flight Crew Diverted; Flight Crew Landed As Precaution
Contributing factors: Weather
Primary problem: Weather

Narrative: We were flying 10;000 MSL; on the VXX from ZZZ - ZZZ1. Along our route we were paralleling a few cells; unsure if it was rain or snow. Closer to ZZZ the freezing level was around 9000 ft. As we continued on our route the temperatures began to drop. We were maintaining clear of the clouds until we found ourselves in-between 2 layers with no presence of rain snow. All of a sudden; we began to notice that there was precipitation in between the two layers; we attempted a 30 degree heading change to the left to exit conditions. Prior to flying in-between cloud layers; the area to the left of the VXX appeared clear. As we continued on our heading; we began to pick up ice very quickly. We continued the turn 90 degrees and started a shallow descent down. At this point ATC was requesting us to climb to 10;000 ft for the MIA (Minimum IFR Altitude) and we were unable as our performance was decreasing due to the increase in structural ice and what I assume was induction ice since we also lost about 300 RPMs. We continued a turn to 180 as ATCs vector to a west heading for lower terrain was not putting us in warm enough temps to melt off the ice and we were unable to maintain the current altitude and descending below 9;000 ft. At this point we were flying back towards the an area were mountains would not be an issue; while still continuing to descend and trying to maintain a safe airspeed. After a few minutes of flying and descending; we found some VMC conditions near a mountain top that had a very flat area. We cancelled IFR and decided to descend down into that area and remained clear of the terrain and began to circle and descend into warmer temperatures to try and melt the ice off. We circled at least 10 times and for about 15 minutes before the structural icing was off the wings. At this point; this pocket of VMC conditions was closing up and we made a decision to fly east through a corridor of VMC conditions towards ZZZ2 since it was the closest airport. After flying around the area; the only way in was following the GPS approach in. We were able fly in between layers on the course and eventually found a hole to descend down to minimums through. Once at minimums; we saw the runway and made the circle to land for Runway 24 and although we observed no more structural ice; we still conducted a zero flap approach to land.




Synopsis: C172 Pilot reported weather diversion due to inflight icing conditions with aircraft not equipped with anti-ice protection.