What happened
The pilot was operating the aircraft during a scheduled maintenance test flight. During the operation, the engine RPM dropped unexpectedly. Shortly after this drop, a series of loud bangs were heard from the engine compartment, followed by a complete loss of power. The pilot attempted to control the aircraft and executed a forced landing in an unprepared, rough field.
The investigation
Following the accident, the engine was examined to determine the cause of the failure. The inspection revealed that No. 1 piston had failed mechanically. Records indicated that the engine had accumulated only 43 hours of flight time since its last overhaul.
Findings
The mechanical failure of the piston led directly to the loss of engine power. The pilot was forced to land in a rough field due to the sudden cessation of thrust. The short duration of operation since the last overhaul suggests a potential manufacturing or assembly defect rather than wear-related failure.