On July 19, 1992, a Cessna 120 (registration N89970) operated by Hicks, Timothy J. was involved in an aviation accident near Reserve, LA. Investigators recorded the probable cause as: The separation of the number one cylinder exhaust valve, which led to its ingestion into the engine and subsequent complete engine failure. This summary draws on records from the U.S. National Transportation Safety Board (NTSB) historical archive.
A complete engine failure occurred shortly after takeoff as the aircraft passed through 200 feet above ground level. The pilot was forced to land in a rough open field because no other suitable terrain was available nearby.
What happened
The pilot reported experiencing a complete engine failure while the airplane was climbing out after takeoff. At the time of the failure, the aircraft was passing through an altitude of 200 feet above ground level. With no other suitable terrain available in the immediate vicinity, the pilot was forced to land the airplane in a rough open field.
The investigation
Post-accident examination of the engine revealed significant internal damage. Investigators found that the exhaust valve for cylinder number one had separated from its stem. The stem was subsequently ingested into the engine mechanism. Additionally, the head of the valve was discovered embedded within the piston head. Due to the extensive level of damage sustained by these valve components, investigators were unable to determine the exact mode of failure.
Findings
The primary contributing factor was the separation of the no. 1 cylinder exhaust valve. The ingestion of the valve stem and the embedding of the valve head in the piston caused the complete loss of engine power.
Probable cause
The separation of the number one cylinder exhaust valve, which led to its ingestion into the engine and subsequent complete engine failure.