Before takeoff, the private pilot completed a preflight inspection, engine start, and two engine run-ups with no anomalies noted.
Shortly after takeoff, when the Zenith CH 750 was about 400 feet above ground level, the engine began to vibrate, and the pilot noticed a partial loss of power. He suspected carburetor icing and applied carburetor heat but observed no change to the engine power.
Due to the low altitude, he chose to execute a forced landing to a field near Temple, Texas. The airplane touched down in the soft field, and the nose gear collapsed.
Post-accident examination of the airplane, which included the fuel system, revealed no evidence of preimpact mechanical malfunctions or failures that would have precluded normal operation.
The pilot reported that he should have applied carburetor heat before takeoff to clear any potential ice buildup during the taxi and subsequent engine run-ups.
The airplane was operating in an area with weather conditions conducive to the formation of serious carburetor ice at glide power settings. The partial loss of engine power was likely due to an accumulation of carburetor ice while operating at reduced engine power settings before takeoff.
Probable cause: The accumulation of carburetor ice before takeoff, which resulted in a partial loss of engine power on initial climb and a forced landing on unsuitable terrain.
This September 2018 accident report is provided by the National Transportation Safety Board. Published as an educational tool, it is intended to help pilots learn from the misfortunes of others.