Primary finding
Probable cause
The total loss of engine power during cruise flight due to fouled spark plugs, which resulted from a stuck mixture control.
Investigator assessment
Analysis narrative
The pilot reported that the airplane was in level cruise flight when the engine began to run rough and lose power, followed by a complete loss of engine power. He made a forced landing on a mountain ridge. During the forced landing, the nose wheel encountered rough terrain and collapsed rearward, which resulted in substantial damage to the fuselage. Postaccident examination revealed that the engine’s mixture control malfunctioned, which resulted in fouled spark plugs.
Source record
Factual narrative
The pilot reported that while in level cruise flight the engine began to run rough and lose power, followed by a complete loss of engine power. He made a forced landing to a trail on a mountain ridge. During the forced landing, the nose wheel encountered rough terrain and collapsed rearward. The airplane sustained substantial damage to the fuselage. A postaccident examination by the pilot, revealed the mixture control stuck in the full rich position, which fouled the spark plugs.