What happened
Approximately one hour after departure from the origin airport, the aircraft engine began to run roughly. The pilot conducted a magneto check and observed a significant drop of 300 RPM on one side. Due to the deteriorating engine performance, the pilot decided to execute a precautionary landing in an adjacent field of tall wheat.
During the landing roll, the left main landing gear struck a hole in the ground. This impact caused damage to the aircraft structure and landing gear components. The pilot reported that the engine had been running rough prior to the touchdown, which was the primary reason for selecting the field as a landing site.
The investigation
Following the accident, investigators examined the engine to determine the cause of the rough running condition. The examination revealed that the bottom spark plugs were fouled. This fouling likely contributed to the uneven engine operation and the subsequent decision to land in the field.
Findings
The primary factors leading to the accident included:
- Engine performance degradation due to fouled spark plugs
- The decision to land in a field with potential terrain hazards
- Impact of the left main landing gear with a ground hole during the landing roll
The investigation concluded that the engine's rough running condition was directly linked to the condition of the spark plugs. The pilot's choice to land in an unprepared area introduced additional risks, which resulted in structural damage when the gear struck a depression in the field.