Event
During cruise flight, the engine experienced a partial loss of power, with the revolutions per minute (rpm) decreasing from 2,300 to 1,200. The pilot responded by applying carburetor heat, but engine power was not restored. Subsequently, the pilot executed a forced landing in an open field. During the landing, the nose gear collapsed.
Examination
An examination of the engine revealed no evidence of internal component failure. The engine was inspected for any mechanical issues that could have caused the power loss, but none were found.
Conditions
Review of a carburetor icing probability chart disclosed that the temperature and dew point at the time of the event were within an area of the chart annotated "Moderate Icing -- Cruise Power or Serious Icing Descent Power." This suggests that atmospheric conditions were conducive to carburetor icing at the time of the power loss.