Accident Sequence
While returning to the airport following an instructional flight, the engine experienced a sudden power drop of 1300 to 1400 RPM, according to the certified flight instructor (CFI). The CFI proceeded through the emergency checklist but could not maintain altitude. When the left magneto was selected, the engine lost all power. The CFI executed a forced landing on short, soft, and hilly terrain, during which the airplane nosed over.
Examination Findings
An examination of the airplane revealed no mechanical malfunctions. Both magnetos were functionally tested and met the manufacturer's tolerances. The flap selector switch was found in the fully extended position, but the flaps themselves were in the retracted position. The carburetor heat control was found in a midway position.
Environmental Conditions
The temperature and dew point were 38°F and 20°F, respectively. According to carburetor icing probability charts, these conditions were conducive to visible icing at glide and cruise power.