Incident Summary
While descending to the planned destination, the airplane experienced a total loss of engine power. The pilot executed an emergency landing in a nearby open field. The touchdown was successful in the recently plowed terrain; however, during the landing roll, the airplane struck an irrigation pipe and nosed over onto its back. This sequence resulted in buckling of the fuselage and crushing of the top one foot of the vertical stabilizer.
Engine Examination
A post-accident partial disassembly of the engine was conducted by the Investigator-In-Charge. Examination revealed that the oil galley in the number four crankshaft connecting rod journal had become partially blocked by unidentified debris. This blockage led to insufficient lubrication of the number four connecting rod bearing, causing its ultimate thermal destruction. Subsequent direct contact between the connecting rod and the crankshaft journal, combined with thermal distress, resulted in the failure of the connecting rod cap. The cap failure allowed the connecting rod to separate from the crankshaft journal, leading to internal engine failure and total loss of power.
Damage
The aircraft sustained structural damage during the nose-over, including fuselage buckling and crushing of the vertical stabilizer's upper section.