On February 23, 1994, a Schweizer G-164B (registration N36265) was involved in an aviation accident near Clarksburg, CA. Investigators recorded the probable cause as: Detonation resulting from an overly lean mixture led to fatigue failure of the No. 1 cylinder at its spark plug holes, causing a total loss of engine power. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
An airplane experienced a total loss of engine power shortly after departing a privately owned airstrip, prompting an emergency landing on a plowed field during which the aircraft nosed over. Examination revealed the No. 1 cylinder failed due to fatigue originating at its spark plug holes, with detonation from an overly lean mixture.
Accident Sequence
Shortly after departing a privately owned airstrip, the airplane sustained a total loss of engine power. The pilot executed an emergency landing on a plowed field. During the landing roll, the airplane nosed over.
Examination Findings
An examination of the engine was conducted. The No. 1 cylinder had failed in fatigue, with the failure originating at its spark plug holes. The combustion signatures on the cylinder head indicated that the engine had been exposed to this operating condition for some time. The detonation that led to the fatigue failure resulted from too lean of a mixture.
Conclusion
The total loss of engine power was the direct result of the fatigue failure of the No. 1 cylinder, which was caused by detonation stemming from an excessively lean fuel-air mixture.
Probable cause
Detonation resulting from an overly lean mixture led to fatigue failure of the No. 1 cylinder at its spark plug holes, causing a total loss of engine power.