Primary finding
Probable cause
A complete loss of engine power as a result of carburetor ice due to the pilot’s failure to effectively use carburetor heat in conditions conducive to the formation of carburetor ice.
Investigator assessment
Analysis narrative
The pilot reported that when he increased the engine throttle during cruise flight, the engine rpm lagged, and he heard the engine “stutter.” He applied full carburetor heat, and the engine rpm dropped over 600 rpm, and it sounded like it was going to quit. He closed off the carburetor heat immediately and began to circle an airport in case of an engine failure. The pilot began to slowly add carburetor heat in small increments to melt the ice from the carburetor. After about five minutes of slowly adding carburetor heat, he determined that the carburetor ice had all melted off and the engine was operating normally. After determining the engine was running properly, he continued towards his destination. He periodically applied full carburetor heat for 30 to 60 seconds at a time. About two miles from his destination the pilot applied carburetor heat, and the engine began to again “stutter.” The pilot again slowly increased the carburetor heat to gradually melt the ice buildup in the carburetor. The engine continued “sputtering” and running very rough and then lost total power. The pilot attempted to restart the engine twice to no avail. The pilot trimmed the airplane for the best rate of glide and began looking for a place for an emergency landing. The pilot made a forced landing to a short narrow gravel road surrounded by tall spruce trees and alders. During the landing rollout a strong gust of wind pushed the airplane to the right and the right wing impacted a spruce tree. The plane spun 180 degrees and came to rest into trees sustaining substantial damage to both wings. Weather conditions at the time of the accident were conducive to the formation of serious carburetor icing at cruise power. The pilot reported that there were no mechanical malfunctions or failures with the airplane, engine, or related systems that would have precluded normal operations.