Incident Overview
During an instrument flight rules (IFR) flight at approximately 11,000 feet mean sea level, the airplane's engine began to run rough and engine oil pressure dropped to zero. The pilot also reported smelling something burning. He initiated a descent and requested vectors to the nearest airport. While following the vector, the engine roughened further and the burning smell intensified. The pilot then shut down the engine and entered a power-off forced landing.
Forced Landing
The pilot broke out of the clouds and determined that he could not glide to the airport. He performed a landing to the only available area. During touchdown, the airplane collided with posts.
Post-Accident Examination
An FAA safety inspector examined the engine. He determined that one of the four bolts used to secure the engine oil pump cover to the crankcase was missing. A damaged bolt was found in the engine's camshaft gear. The tab washers used to lock the oil pump cover bolts were found with their single tab bent downward. The twin tabs on the three remaining bolts were pointed straight out, appearing to have never been bent into place after the bolts were tightened.
Findings
Improper installation of the washers resulted in one bolt falling off and being ingested through various drive gears. The engine had been overhauled by the manufacturer 515 hours prior to the accident.