What happened
The pilot and passenger were completing a cross-country, state-government flight when they began a straight-in approach for landing. Approximately 600 feet above the ground, the pilot applied carburetor heat in preparation for the arrival. Following this action, the engine began to run rough.
As the aircraft descended to approximately 300 feet above the ground, the pilot increased the throttle. At that moment, the engine lost power, necessitating an emergency landing off the left side of the runway. The occupants were not injured.
Weather conditions at the time were clear, with a temperature of -2 degrees F and a dew point of -8 degrees F. The pilot noted the presence of visible ice crystals during the flight.
The investigation
An examination of the engine following the recovery of the aircraft revealed no mechanical malfunctions. During testing, the engine was able to run at idle RPM with the carburetor heat control in both the 'Hot' and 'Cold' positions.