Accident Summary
Approximately 10 minutes into the flight, the engine began to run roughly. The certified flight instructor (CFI) performed the emergency checklist and identified two open fields for a potential forced landing. During the approach to the second field, a construction vehicle entered the flight path. The CFI shortened the approach and elected to land in the first field. On the landing roll, the nose wheel dug into the dirt, causing the airplane to nosed over.
No mechanical anomalies with the engine sound or gauges were noted prior to the loss of engine power.
Engine Examination
An external examination of the engine revealed that the left muffler end cap had separated in an outward direction. The separation extended approximately 350 degrees in circumference at a 45-degree angle. This allowed heat to be directed at the firewall. The P-leads located within the electrical harness were found melted, which allowed the conductors to short within the wires.