Accident Overview
The airplane was in cruise flight under visual flight rules at an altitude of 8,500 feet mean sea level when the pilot experienced a sudden loss of engine revolutions per minute. Air traffic control provided vectors to the nearest airport, approximately 8 miles away, but the aircraft could not glide to the runway.
Forced Landing
With insufficient altitude to reach the airport, the pilot attempted a forced landing in a snow-covered field. The only available illumination was moonlight. During the landing attempt, the airplane struck trees and terrain, subsequently catching fire.
Post-Accident Examination
A detailed examination of the engine revealed no mechanical anomalies. However, disassembly of the carburetor disclosed a brown, gooey substance present in the inlet fuel screen and on the float valve. This substance restricted the movement of the float valve.
Laboratory Analysis
The substance was sent to the National Transportation Safety Board's materials laboratory for analysis. Fourier Transform Infrared Spectroscopy (FTIR) identified the material as "most likely an inorganic compound." Further Energy Dispersive Spectroscopy (EDS) analysis of various samples showed high peaks of carbon in some samples, while others exhibited high peaks of sulfur, and still others high peaks of calcium and silicon.
Fuel Additive Residue
The laboratory report noted that when aviation gasoline evaporates, various additives—such as anti-knock compounds, dyes, inhibitors, and anti-icing compounds—remain behind in the form of a gum. This gum-like residue is consistent with the brown gooey substance found in the carburetor.