Date: 202104
Local time of day: 1801-2400
Location: ZZZ.ARTCC, US
Flight conditions: Mixed
Weather elements / visibility: Icing; Rain; Snow; 10
Aircraft: RV-10
Operator: Personal
Operating under: Part 91
Flight plan: IFR
Mission: Personal
Flight phase: Cruise
Airspace: Class E ZZZ
ATC / advisory: Center ZZZ
Aircraft component: Elevator ControlSystem
Component problem: Improperly Operated
Reporter organization: Personal
Reporter function: Pilot Flying; Single Pilot
Reporter qualification: Flight Crew Commercial; Flight Crew Instrument; Flight Crew Multiengine
Human factors: Fatigue; Situational Awareness; Workload
Anomaly: Aircraft Equipment Problem Critical; Inflight Event / Encounter Loss Of Aircraft Control; 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; Flight Crew Regained Aircraft Control; Flight Crew Requested ATC Assistance / Clarification; Flight Crew Took Evasive Action
Contributing factors: Aircraft; Human Factors; Weather
Primary problem: Ambiguous

Narrative: I was in cruise on IFR flight plane in VMC talking with Center at 15000 ft. The cloud tops were rising and I requested a climb to 17000 ft. to avoid the tops. The sun had set and light was fading. I initiated a slow climb and monitored my wing leading edges with a flashlight as I flew in and out of a few thin tops. I observed a trace; to light amount of mixed ice. Center advised a jet reporting tops at FL190 and asked if I wanted FL190. I replied I could try but did not think I'd make it due to aircraft performance. Upon reaching 17000 ft.; the aircraft did not level off while the autopilot was engaged. I had been monitoring my AoA [Angle of Attack]; 200-300 FPM climb resulted in AoA active; but well above donut; and noticed the aircraft remaining in a 200 FPM climb. I disconnected the autopilot (AP) as the AP commanded full nose down trim. I commanded a nose down control input via the control stick and could not move the stick in a fore or aft motion. I still had roll control but had no pitch control. I applied considerable force - I was afraid of pushing too hard and breaking something; not knowing what had frozen the controls - and could not induce a nose down attitude. I asked for an immediate descent with Center and was granted an altitude of 15000 ft.ADSB weather indicated a heavy to extreme precipitation below my position with bases of 6 - 8000 ft. I commanded full up elevator trim and confirmed movement via trim indication and a reduction in climb rate. I visually confirmed the elevators were stuck in an approximate 10-degree nose up position and could see the counterweights below the horizontal stabilizer. I reduced power slowly and kept considerable forward pressure on the stick; which resulted in a 600-800 FPM descent rate with the same AoA and attitude. I was able to maintain roll control and kept wings level. Yaw control was adequate. I made minimal yaw and roll control inputs to avoid a spin and [requested priority handling] with Center; advising loss of control. They asked which airport I requested and I replied I just need to get lower and asked for the freezing level. I observed OAT at 17000 ft. to be approximately 18-20°F and watched it steadily increase as I descended. I found a power setting that would keep the AoA above [the] donut; keeping an adequate IAS while getting 800-1000 FPM descent.At 14000; precipitation was heavy snow and I observed static discharging on the leading edges of the wings via sparks. Around 11000 ft.; I was preparing for the elevators to become unfrozen; as I suspected ice had formed and frozen them in position during the slow climb; and was prepared for a rapid nose down movement. The elevators did break loose and I was able to recover the nose down attitude quickly and accurately with the maneuver similar to a power-on stall recovery. While still descending; I commanded several nose up and nose down control inputs with increasing force to ensure controls were still functioning and ensuring I had not broken anything. I then worked with Center to pick my destination and requested lower to get into rain. I observed light to moderate mixed and clear icing at that time on the wings and increased my IAS. Once I was in the heavy rain; the ice melted and the aircraft remained responsive to all controls with the engine performing nominally. I asked and was given vectors for the RNAV XX approach but was only cleared down to 6000 ft. at ZZZZZ; 3000 ft. higher than the approach depicted. Upon reaching 6000 ft. and turning inbound; I was switched to Advisory and was VMC with the field in sight. I executed a 360 turn to lose altitude and then flew the pattern to further reduce altitude; executing a normal landing in heavy rain on Runway XX. I called Center on the phone to cancel IFR.On the ground; I visually inspected all control surfaces; tested trim and autopilot functions; and removed several panels to inspect the control push-rods; finding no abnormalities. I checked weather; refiled;and continued to my destination at a lower altitude.My desire to stay above the tops at night near the upper limits of adequate climb performance resulted in inadvertent flight into icing conditions. I believe the slow; sustained climb resulted in minimal elevator inputs and adequate time for ice to build up on the counterweights; freezing the elevators in place. I believe I had more clear ice than I could observe via flashlight. I should have avoided the situation by either climbing earlier to ensure [that I] remained clear of the clouds or descended into warmer temperatures. I could have also diverted or turned around. I had already flown 6.5 hours for hire in IFR and hazardous weather conditions in the PC-12 and fatigue was a factor. I was on supplemental oxygen and remained alert and coherent during the entire event. I credit excellent training - power for altitude; pitch for speed - and upset recovery training during PC-12 initial training; to keeping limited control of the aircraft and avoiding a stall; which would have most likely resulted in a stall/spin and fatal crash.




Synopsis: Single Pilot reported flying into icing conditions and the control surfaces freezing.