On November 4, 1990, a Christen Industries A-1 (registration N9609G) operated by Heiner, Mark G was involved in an aviation accident near Afton, WY. Investigators recorded the probable cause as: The carburetor heat valve was secured in the cold or off position, preventing the application of carburetor heat while the airplane was operating in icing conditions. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An airplane experienced a loss of engine power during a cross-country flight. The forced landing resulted in the aircraft striking a ditch and nosing over. Investigation revealed a modification securing the carburetor heat valve in the cold position, preventing application during icing conditions.
Incident Overview
During a cross-country flight, the airplane suffered a loss of engine power. The pilot executed a forced landing, but during the landing roll, the airplane struck a ditch and nosed over.
Engine Inspection Findings
An inspection of the engine revealed that the carburetor heat valve had been secured in the cold or off position. This modification prevented the application of carburetor heat. At the time of the engine failure, the airplane was operating in conditions conducive to carburetor icing. No other mechanical failures or malfunctions were discovered.
Conclusion
The investigation determined that the carburetor heat valve modification was the only anomaly found.
Probable cause
The carburetor heat valve was secured in the cold or off position, preventing the application of carburetor heat while the airplane was operating in icing conditions.