Incident Sequence
The pilot had flown the airplane four days prior to the accident. After that flight, the electrical master switch was inadvertently left in the "ON" position, resulting in a discharged battery. To start the engine for the subsequent flight, the pilot connected electrical power to the airplane's exterior battery receptacle.
After boarding and starting the engine, the pilot set the engine rpm to a low setting. The pilot then exited the airplane to remove the external power source and the wheel chocks. While the pilot was outside, the airplane began to move forward. Despite the pilot's attempt to stop it, the unoccupied airplane taxied across the airport into a wet field and impacted a small ditch.
Findings
The investigation did not provide further details regarding aircraft type, registration, operator, location, or any injuries. The source report does not specify a probable cause.