What happened
Following recent maintenance involving an oil and filter change, as well as the replacement of the oil temperature and pressure gauges, the pilot prepared the Cessna (type not specified in source) for flight. After verifying the oil level and completing a preflight inspection with no anomalies noted, the aircraft departed.
While cruising at 2,500 feet and 95 mph, the pilot observed erratic behavior in the oil pressure and temperature gauges. The oil pressure rose above 50 psi, then dropped below 40 psi and eventually reached 0 psi before the engine seized. The pilot initiated a forced landing, maneuvering the aircraft under power lines to land on a road. During the landing roll, the aircraft hit a bump, bounced, and touched down again.
In an attempt to avoid a tree on the right, the pilot applied left rudder, causing the right wing to strike a tree and separate from the fuselage. The aircraft then turned right and the left wing struck another tree. Finally, the aircraft turned left and collided head-on with a third tree, coming to a complete stop. The pilot was not injured.
The investigation
Investigators examined the engine and found that the oil temperature and pressure lines were attached and undamaged. However, the oil dipstick cap had separated from the dipstick, and the spring from the cap was found lodged in an engine mount on the right side of the firewall. No oil was found on the engine case halves or within the engine compartment.
Upon disassembly of the engine, it was discovered that the No. 1 cylinder connecting rod had separated from the rod journal. This specific area exhibited heat discoloration, and the rod cap bearing was partially melted and displaced. Additionally, the oil inlet for the No. 1 rod journal was partly melted and blocked. While no metal particles were found in the oil filter or screen, the rear accessory gears and crankcase halves were dry. Only fifteen ounces of black oil were drained from the sump, though a small amount of clear oil was present in the valve covers.