Incident Overview
A pilot completed a fly-by down the runway when the engine experienced a partial loss of power. Subsequently, the airplane entered a spin and impacted the ground in a steep descent. Control continuity was established after the accident, and an examination of the airframe and engine did not reveal any discrepancies.
Witness Account
A witness reported that the airplane was flown down the runway at 90 to 100 miles per hour at a low power setting, followed by a pull-up at the end of the runway.
Carburetor Considerations
According to Bendix Aircraft Carburetor Service Bulletin Number 74, this type of maneuvering, combined with an abrupt throttle movement, may cause the engine to lose power or quit. The accident airplane's carburetor was not equipped with an accelerator pump.
Environmental Conditions
The temperature and dew point were reported to be 77 and 49 degrees Fahrenheit, respectively. According to icing probability charts, these conditions were conducive to carburetor icing. The carburetor heat control knob was found in the 'off' position.
Investigation Findings
No mechanical anomalies were found during the inspection of the airframe or engine. The investigation focused on the carburetor's configuration and the environmental factors that could lead to carburetor icing.