Incident Overview
During cruise flight over mountainous terrain, the pilot observed a drop in oil pressure, which was immediately followed by engine seizure. The pilot initiated a forced landing into rugged terrain, resulting in the destruction of the airplane.
Pilot Actions
The pilot reported that she had checked the oil level prior to the flight and found it adequate. She also stated that the airplane could not have been flown for more than about eight hours since its last inspection.
Post-Accident Examination
Examination of the engine revealed that the No. 6 connecting rod had separated due to a lack of lubrication and bearing seizure. No evidence of leaking oil was found on the underside of the airplane. The rubber seal around the No. 6 push rod tube was found detached after salvage, but investigators could not determine whether this condition existed before impact.
Maintenance Context
The oil had last been changed approximately one month prior to the accident. According to a maintenance log entry and the accident tachometer time, the airplane had flown about 23 hours since the oil change.
Oil Loss Investigation
The published usable oil quantity for the engine is 5.6 quarts in a 5-degree nose-down attitude. Despite examination, conclusive evidence for the loss of engine oil could not be determined.