What happened
The incident occurred during a night cross-country flight operation. While airborne, the aircraft's engine suddenly lost power. The pilot initiated a forced landing procedure to manage the emergency situation. During this maneuver, the airplane collided with trees and subsequently impacted the terrain.
The investigation
Following the accident, investigators conducted a partial teardown of the engine to determine the mechanical cause of the power loss. Examination of the internal components revealed significant damage within the cylinder assembly. Specifically, the number 3 cylinder exhaust valve rocker arm shaft was found to have broken. Additionally, inspectors noted a large gap between the rocker arm and the exhaust valve stem, indicating a failure in the valve train mechanism.
Findings
The mechanical failure of the number 3 cylinder exhaust valve rocker arm shaft directly contributed to the loss of engine power. This internal component failure prevented proper operation of the exhaust valve, leading to the cessation of engine function while the aircraft was in flight. The subsequent impact with trees and terrain was a direct result of the inability to maintain altitude due to this mechanical failure.