Amateur-built CASSUTT N78RM accident near Louisville, Nebraska

Probable cause

The pilot's decision to operate with partial carburetor heat while operating in conditions conducive to the formation of carburetor ice, which resulted in a loss of engine power due to carburetor icing.

NTSB analysis

During a local flight, the pilot noticed the engine was running rough when he added power. He attempted to troubleshoot the problem; however, the engine continued to run rough, and the pilot performed a forced landing to a field. The landing gear collapsed, and the airplane came to rest upright. A postaccident examination of the airplane and engine found no mechanical malfunctions or failures that would have precluded normal operation. The pilot reported that he routinely flew with a partially-open carburetor heat setting. Since the weather conditions around the time of the accident were conducive to the formation of carburetor ice at glide and cruise power, it is likely that the partial carburetor heat setting and the lower power setting increased the engine's susceptibility to the formation of carburetor ice, resulting in the rough-running engine. When the pilot changed the throttle setting, full power was not available due to the ice formation.

Text from the NTSB. Open the NTSB docket for CEN16LA133 for the full record.