Engine Failure Leads to Emergency Landing and Collision with Sign (N758CQ)

Incident Description

After climbing to 3,500 feet, the pilot observed smoke entering the cockpit and the engine beginning to run roughly. The pilot diverted back toward the departure airport, but noted a rapid drop in oil pressure and fluctuating RPM. Deciding to secure the engine, the pilot executed an emergency landing on a gravel road. During the landing roll, the right wing struck a yield sign on the side of the road.

Examination Findings

Subsequent inspection revealed no oil on the dipstick. A two- to three-inch hole was found in the engine crankcase. Disassembly of the engine showed a hole burned through the number three piston. The number one and number two connecting rods were detached from the crankshaft, and the corresponding crankshaft journals were partially melted. The fuel system was checked and found free of defects. Examination of the magnetos disclosed that the race inside the left magneto was loose and rotating within the aluminum housing, with metal particles from the race and housing covering the surface around the magneto block.