Accident Summary
During cruise flight, the engine lost oil pressure. The pilot continued flying in an attempt to return to the departure point. However, the engine seized before reaching that point. The pilot executed a forced landing onto unsuitable terrain, resulting in substantial damage to the airplane. The pilot and a pilot-rated passenger were not injured.
Examination Findings
Post-accident examination of the engine revealed that the two bottom attachment screws for the upper (left) vacuum pump were loose. Approximately one quart of oil was found in the engine and oil filter. The underside of the airplane was coated with oil from the firewall to the tail mooring point. No anomalies were found with the oil pump or oil lines.
Maintenance Record Review
A review of the airframe maintenance logbooks showed that the left vacuum pump had been removed and replaced on the same day of the accident, prior to the accident flight.
Oil Leak Test
An oil leak test was performed on another Cessna 172R. The two lower nuts of the upper vacuum pump were loosened, and the engine was run near full static RPM for five minutes. Oil began leaking from the vacuum pump as soon as the engine started. After five minutes, the back of the engine, the lower cowling, engine accessories, and the ground were partially covered with oil.
Emergency Guidance
According to the Cessna pilot operating handbook, under emergency procedures, the pilot should have landed at the nearest airport to inspect for the source of the loss of oil pressure.