Accident Sequence
While descending for landing with the engine power set at 23 inches of manifold pressure and 2,300 rpm, the pilots heard a loud noise and observed something exiting the cowling. This was followed by an abrupt loss of engine power, severe engine vibration, and the appearance of light blue smoke in the cockpit. The pilots executed a forced landing onto a dirt road. During the landing roll, the airplane struck a sand dune, causing the aircraft to bounce and subsequently nose over.
Post-Accident Examination
A detailed examination of the engine after the incident disclosed that the #1 piston had fractured into two halves. The upper half of the piston remained lodged in the upper (outer) portion of the #1 cylinder, while the lower half was destroyed. The connecting rod and its cap bolt had separated. The camshaft and its splined end, where it attaches to the oil pump, were found damaged, and the oil pump had seized. Inspection of the rod cap bolts revealed 'necking down,' a condition consistent with tension overload.
Engine History
The engine had accumulated 1,464.7 hours of flight time since new and 915.1 hours since its last major overhaul.