Incident Details
The airplane was in level flight at 3,000 feet when the engine began to run rough. The pilot cycled the magneto switch and noted no changes in engine performance. Subsequently, the pilot observed the oil pressure gauge indicating zero. The engine then lost total power, and the pilot performed a forced landing to a field.
Engine Examination
Following the forced landing, the engine was examined. A 2-inch hole was found in the top of the engine crankcase. The connecting rod and camshaft area of the number four cylinder had sustained extreme heating. The bottom half of the connecting rod was bent out of shape, with one of the rod end bolts remaining wedged in the rod end. The other rod end bolt was missing. No evidence of oil leakage was observed.
Maintenance History
The engine had accumulated about 2,400 hours of operation since its last overhaul. An annual inspection of the engine was performed about 3 months prior to the accident. A 50-hour inspection, which included servicing the engine with 7 quarts of oil, was conducted 2 days prior to the accident.