Narrative
Shortly after leveling off to cruise altitude, the engine began to lose power. The pilot attempted to restore engine power, but the engine RPM continued to decrease. The pilot executed a turn back toward the departure airport. While scanning the instruments, the pilot observed zero oil pressure and a high oil temperature reading. Soon after, the engine ceased operating, and the pilot was unable to restart it. The pilot performed a landing in an open field. During the landing roll, the aircraft struck a ditch and nosed over.
Investigation Findings
An investigation revealed that the engine oil pump (part number LW-12897) had failed. A teardown inspection of the pump showed that a tooth had broken off and become wedged in the gear housing. Additionally, the inner walls of the gear housing exhibited scoring marks. The applicable Airworthiness Directive (AD 81-18-04) addressed this engine and pump combination, but it would not have become applicable until 2000 hours after overhaul or until the accessory section was removed. When applicable, the AD would have required replacement of the iron sintered impeller with a hardened steel impeller. At the time of the incident, the engine had accumulated 1410 hours since overhaul.