The flight instructor reported that, during a long cross-country flight, they encountered deteriorating weather conditions, and to remain in visual flight rules, he altered course and destination.
En route and while approaching a ridge line, he “noticed that the Cessna 150’s airspeed started to drop toward 65 miles an hour.”
He added that “he thought that maybe the airplane was picking up carburetor ice and he reached for the carburetor heat and pulled it out.”
The student pilot reported that, after the flight instructor stated, “watch your airspeed,” he looked at the rpm gauge and noted that it was indicating 1,800 to 1,900 rpm. He added that the flight instructor took over the flight controls and that the airplane then hit the top of a ridge near Zepp, Virginia. The airplane sustained substantial damage to the right wing.
Atmospheric conditions reported at the time of the accident around the accident site were conducive to serious icing at cruise power. It is likely that carburetor ice accumulated due to the student pilot’s failure to apply carburetor heat and the flight instructor’s delayed application of carburetor heat, which resulted in a partial loss of engine power.
Probable cause: A partial loss of engine power due to the formation of carburetor icing, which resulted from the student pilot’s failure to apply carburetor heat and the flight instructor’s delayed response in applying carburetor heat while operating in conditions conducive to carburetor icing.
NTSB Identification: GAA17CA306
This May 2017 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.