Incident Overview
An airplane manufactured in 1964 was loaded to within a few hundred pounds of its maximum gross takeoff weight. It departed from an airport situated in a valley surrounded by rising terrain. Although visual conditions prevailed at the accident airport, fog was present in adjacent valleys.
Engine Failure
During the initial climb after takeoff, the right engine experienced a partial power loss. The failure was attributed to a failure of the number one cylinder exhaust valve. The pilot secured the right engine in response to the loss of power.
Climb Performance
With only the left engine producing power, the pilot was unable to maintain a climb. Review of weight and performance data published at the time of the airplane's manufacture indicated that the airplane should have been capable of climbing approximately 400 feet per minute with a single engine producing power. However, no current weight and balance data was recovered from the accident site. Due to impact and fire damage, the preimpact power output of the left engine could not be determined.
Engine History
Both engines were last overhauled slightly more than 12 years prior to the accident and had accumulated approximately 310 hours of operation since that overhaul. The manufacturer recommended overhaul of this make and model engine at 1,200 hours of operation or during the twelfth year, whichever occurred first.
Probable Cause
The probable cause of the accident was determined to be a partial power loss in the right engine due to the failure of the number one exhaust valve, and the airplane's inability to maintain a climb on one engine for unknown reasons. Contributing to the accident were fog and rising terrain.