What happened
The aircraft was operating under instrument flight rules while descending toward the planned destination. During this phase of flight, the engine began running roughly. The pilot took immediate action to improve engine performance by applying carburetor heat. Despite these efforts, the engine did not recover sufficiently for a continued instrument approach.
The pilot initiated a localizer-only approach but was unable to see the runway at the minimum descent altitude. Consequently, a missed approach procedure was executed. The pilot intended to divert back to Omaha, Nebraska. However, while en route to the alternate airport, the aircraft was unable to maintain altitude due to the continued loss of engine power.
At approximately 500 feet above ground level, the pilot regained visual references with the terrain below. Recognizing the inability to continue flight, the pilot selected a field covered in snow for an emergency landing. A soft-field approach and landing were attempted on the uneven surface. During the touchdown and rollout, the aircraft dropped off a terrace onto another section of the field. The terrace was not visible from the air due to the extensive snow cover, which concealed the change in elevation.
The investigation
Following the accident, an examination of the aircraft was conducted to determine the mechanical cause of the engine failure. Inspectors found that the carburetor fuel nozzle was covered with ice. This blockage restricted fuel flow, leading to the rough running and subsequent loss of power. Further testing confirmed that the carburetor heat system itself was operational and functioned as designed during the pre-accident phase.