Incident Overview
During descent toward the planned destination, an engine began running rough. The pilot attempted to improve engine performance by using carburetor heat. A localizer-only approach was conducted, but the pilot was unable to see the runway at the minimum descent altitude. A missed approach was executed, and the pilot started to divert back to Omaha, Nebraska.
Loss of Altitude and Forced Landing
While en route to the alternate, the pilot was unable to maintain altitude. At approximately 500 feet above ground level, the pilot was able to continue with visual references. He selected a snow-covered field and performed a soft field approach and landing. During the landing, the aircraft was damaged when it dropped off a terrace onto another terrace. The terrace was not visible from the air due to snow cover.
Examination Findings
An examination revealed that the carburetor fuel nozzle was covered with ice. The carburetor heat system was found to be operational.