What happened
During the cruise phase of flight, the flight instructor asked the student pilot if he heard a knocking sound. The student confirmed that the knocking was audible. At that moment, both pilots observed the oil pressure gauge dropping to zero. Simultaneously, the engine knocking intensified, and the engine subsequently quit.
Following the engine failure, an emergency landing was performed. During the landing roll out, the nose landing gear dug into soft dirt, which caused the airplane to nose over.
The investigation
An external examination of the engine showed that the rear of the engine, the firewall, and the bottom of the fuselage were all coated with oil. Further inspection of the engine revealed that the oil filter had not been tightened or safety wired to the engine. A review of the engine logbook indicated that an oil change had been performed the day before the accident.