What happened
The pilot was conducting agricultural spraying operations when the aircraft engine began to skip and backfire. Recognizing the mechanical distress, he decided to terminate the current swath run and climb out of the crop field. As he initiated the climb, the engine quit completely. The pilot managed to gain as much altitude as possible before gliding toward a nearby soybean field for an emergency landing. During the landing phase, the aircraft sustained damage.
The investigation
A physical examination of the aircraft revealed that the carburetor heat ducting was disconnected. This mechanical failure rendered the carburetor heat system inoperative, preventing the pilot from applying heat to prevent ice formation. Weather data from the nearest reporting facility indicated a temperature of 86 degrees and a dew point of 70 degrees. These conditions created a high humidity environment conducive to serious carburetor icing at glide power settings and visible icing at cruise power.
Findings
The primary contributing factor was the inoperative carburetor heat system due to disconnected ducting. The weather conditions were highly favorable for ice accumulation within the carburetor, which led to engine power loss.