What happened
While climbing to cruise altitude, the left engine of the aircraft lost power. This failure was caused by the failure of the intake and exhaust valves in the No. 6 cylinder. In response to the engine failure, the pilot feathered the left propeller and initiated a turn back toward the departure airport.
During the subsequent descent, the right engine also lost power. Following this second engine failure, the aircraft entered a steep descent and crashed into a wooded area. The impact was followed by a massive postcrash fire.
The investigation
Investigators examined the fuel selector valves following the accident. They found that the left engine fuel selector valve was set to the 'on' position, while the right engine fuel and selector valve was in the 'off' position. Additionally, an examination of the mechanical failure in the left engine revealed extensive rocker arm wear which contributed to the valve failures in the No. 6 cylinder.