Hiller-Tri-Plex Ind.Inc. UH-12B N9041U accident near Okeechobee, Florida

Probable cause

The pilot's failure to monitor carburetor temperature and use carburetor heat in conditions conducive to serious carburetor icing, which resulted in partial loss of engine power.

NTSB analysis

While airborne hunting, the pilot was maneuvering the helicopter at low altitude when the engine experienced a partial loss of power. During the subsequent forced landing, the helicopter struck trees and was substantially damaged. Postaccident examinations of the engine and airframe revealed no evidence of mechanical malfunctions or failures that would have precluded normal operation. The atmospheric conditions at the time of the accident were conducive to serious carburetor icing at cruise power. During a postaccident interview, the pilot reported that he did not monitor the carburetor temperature or use the engine carburetor heat during the flight or subsequent to the engine power degradation. Therefore, it is likely that the carburetor accumulated ice, which subsequently resulted in a partial loss of engine power.

Text from the NTSB. Open the NTSB docket for ERA13LA118 for the full record.