What happened
During the initial climb phase following departure, the aircraft experienced a mechanical failure in the right engine. Specifically, the number one cylinder exhaust valve failed, resulting in a loss of partial power from that engine. In response to the malfunction, the pilot successfully secured the right engine. However, the aircraft was unable to sustain its climb using only the power provided by the left engine.
At the time of the incident, the aircraft was loaded very close to its maximum allowable takeoff weight. The departure took place from an airport situated within a valley and surrounded by ascending terrain. While visibility at the departure airport was clear, fog was noted in the neighboring valleys. The aircraft, a 1964 model, was operating in an environment where terrain clearance was a critical factor during the climb.
Findings
Investigation into the engine's condition revealed that both engines had not undergone an overhaul for over 12 years, having accumulated approximately 310 hours of flight time since their last service. This exceeded the manufacturer's recommendation to overhaul the engines at either 1,200 operating hours or upon reaching the twelfth year of service.
Analysis of the original manufacturer's performance data indicated that the aircraft should have maintained a climb rate of approximately 400 feet-per-minute while operating on a single engine. However, due to the extent of the fire and impact damage, the specific power output of the left engine prior to the accident could not be verified. The failure of the number one cylinder exhaust valve was the primary event that initiated the loss of climb capability.