What happened
The incident occurred while the aircraft was operating in cruise flight conditions. During this phase, the engine suddenly lost power, necessitating an immediate emergency response from the pilot. Unable to maintain altitude or reach a suitable airfield, the pilot initiated a forced landing procedure. The attempt was made at night and targeted an interstate highway as the nearest available flat surface.
During the final approach for the forced landing, the aircraft collided with overhead wires. This impact likely compromised the structural integrity of the airplane before it reached the ground. The specific aircraft registration involved in this accident is N12345. The flight phase was critical, transitioning from cruise to an emergency descent and landing attempt under low-visibility conditions.
The investigation
Following the accident, investigators conducted a detailed examination of the engine components to determine the root cause of the power loss. The inspection focused on the valve train assembly, specifically looking for signs of mechanical failure or obstruction.
The technical analysis revealed a fatigue failure within the No. 1 cylinder outer intake valve spring. This structural failure caused the inner spring to become jammed. As a direct result of this jamming, the intake valve was held in an open position. This mechanical fault prevented proper combustion and compression, leading to the complete loss of engine power during cruise flight.
Findings
The primary factor contributing to this accident was fuel exhaustion due to mechanical failure. The fatigue failure of the intake valve spring was the direct cause of the engine stopping. The nighttime conditions and the decision to attempt a landing on a highway added complexity to the survival outcome, but the initial loss of control capability was purely mechanical.
The investigation confirmed that the wire strike occurred during the approach phase, which is consistent with the pilot's attempt to land on a linear feature like a highway in the dark. No other mechanical anomalies were reported as contributing factors.