Incident Overview
While in cruise flight, the aircraft began to lose oil pressure. The propeller rpm ceased to respond to movements of the propeller governor control lever. Eventually, the engine oil pressure dropped to zero, prompting the pilot to attempt a forced landing on a country road. The landing touchdown was successful, but as the aircraft rolled along the road, its wings collided with mailboxes mounted on steel poles placed immediately adjacent to the roadside.
Examination Findings
A post-incident examination of the engine determined that both compression rings on the number four piston had fractured. Additionally, a portion of the piston's outer wall near the piston dome had eroded away. This erosion allowed the majority of the engine's oil to be lost through the exhaust system.
Consequences
The aircraft sustained damage to its wings due to the collision with the mailboxes and their steel mounting poles. No other damage or injuries are mentioned in the investigation report.