Engine Wear and Terrain Encounter Precede Mountain Impact (N5655L)

Engine Examination

The aircraft had accumulated 228 hours of operation since its engine was overhauled by the owners and signed off by an A&P mechanic. During the overhaul, the camshaft was ground and the tappets resurfaced. The Lycoming overhaul manual specifies that if the camshaft is replaced or reground, new tappets must be installed to prevent severe wear and spalling of the cam lobes and tappet bodies. Examination of the engine revealed that the cam lobes and tappets for cylinders #1 and #2 were severely spalled and worn down to approximately half their normal profile. Lycoming technical representatives stated that such cam lobe wear would alter the duration and amount of valve action, thereby reducing the engine's power output capability. Additional discrepancies were found during the examination.

Flight Path and Observed Events

After departure, the aircraft climbed toward the mountains. The terrain rise was about 470 feet per mile, while the aircraft was capable of climbing at approximately 350 feet per mile. Witnesses observed the aircraft approaching the mountain ridge low and slowly, then initiate a left turn as it began descending toward the ground. At the time, high winds were blowing across the ridge, and clouds topped the mountains.