The 1,643.4-hour pilot reported that during cruise flight on a dark night, he saw "sparks under the cowling in front, and lost cylinders one, two, and three, according to the engine monitoring unit installed in the airplane." The pilot attempted to return to the airport, but the engine lost power, and he initiated a forced landing to a field with the flaps and gear retracted. Examination of the airplane revealed visible signs of oil streaks were observed throughout the entire length of the bottom of the fuselage. Flight control continuity was established throughout the airplane at the accident site. Examination of the engine revealed that the oil filter converter plate gasket was extruded in multiple locations. An Emergency Airworthiness Directive (AD) had previously been issued requiring the replacement of the oil filter converter plate gasket, but no entries were found in the airplane maintenance log books pertaining to its compliance.
The National Transportation Safety Board determines the probable cause(s) of this accident as follows:
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