Event Narrative
While in cruise flight at 4,500 feet with an outside air temperature of 35 degrees, the pilot turned on the cabin heat. Approximately 10 to 20 minutes later, the airplane encountered light mist. After continuing for about 40 to 50 nautical miles in deteriorating weather, the pilot decided to turn around.
Engine Performance Issues
Shortly after turning, the engine was not producing full power and was running roughly. The pilot suspected carburetor ice due to high humidity and low outside air temperature. Carburetor heat was applied for about one minute but had no effect. The engine continued to run rough, and the rpm decreased to approximately 2,000 to 2,100. A second application of carburetor heat did not improve engine performance.
Precautionary Landing
Believing he could not safely navigate across higher terrain to reach his destination, the pilot chose to perform a precautionary landing on a logging road. During the landing, the pilot saw a bulldozer on the road and swerved the airplane off the road to avoid it. The left wing subsequently impacted a tree.