What happened
The incident occurred while a student pilot was operating an aircraft at an altitude of 3000 feet. At this time, the aircraft was located approximately 14 nautical miles north of the Danville VOR. The pilot reported that the engine began to vibrate noticeably. Shortly thereafter, the engine lost power completely. Unable to maintain flight, the pilot executed a forced landing in a bean field situated approximately four miles north of the Danville Airport.
The investigation
Following the accident, an examination of the aircraft's engine was conducted to determine the mechanical cause of the failure. The inspection revealed that the adjustment screw in the rocker arm for the number 4 intake valve had worked loose. This mechanical failure prevented the valve from operating correctly, which directly led to the loss of engine power.
Findings
The primary factor contributing to this accident was the loose adjustment screw in the rocker arm assembly. This component failure stopped the number 4 intake valve from functioning, resulting in an in-flight engine shutdown. The pilot's decision to land in a bean field was a direct response to the sudden loss of power at low altitude.
Safety message
Regular maintenance inspections are critical for identifying loose hardware in engine components. Ensuring that adjustment screws and rocker arm assemblies are properly secured can prevent similar valve failures and subsequent engine power loss.