What happened
During an approach at the Central Wisconsin Airport, the crew executed a missed approach on their first attempt and subsequently began a complete procedure turn for the ILS. Both the initial and second approaches were conducted at 3000 feet MSL within IMC conditions characterized by moderate to heavy rain.
A temperature inversion between 5000 feet and 3000 feet MSL created conditions suitable for moderate to severe clear icing. The aircraft remained in these conditions for 11.8 minutes. While flying the procedure turn with the autopilot engaged, the captain reduced power to decrease airspeed in preparation for gear extension.
At a speed of 157 knots in a clean configuration, the aircraft entered a stall, resulting in a roll of 80 degrees to the left and 60 degrees to the right. The crew responded by applying full power and performing stall recovery procedures. The aircraft was recovered following an altitude loss of 600 feet. The third approach was completed without further incident.
Findings
The crew did not perceive any ice accretion on the airframe during the flight. Additionally, the airframe deice system was not activated until after the stall had occurred.