What happened
During an attempt to start the engine via hand propping, the pilot encountered issues with the electric starter. The pilot instructed the passenger, who was seated in the right seat, on how to operate the brake system, specifically regarding the use of the "T" handle brake system and the Johnson brake bar. After setting the throttle between one-quarter and three-eighths of an inch, the engine successfully started.
Upon startup, the engine produced high power, causing the aircraft to move forward. As the aircraft accelerated across the airport, it struck the pilot. The aircraft continued its movement, crossing a runway and a taxiway before colliding with a fence and trees located in a park on the west side of the airport. At the time of the incident, no tie-downs or wheel chocks were in use.
Findings
The pilot reported an inability to understand how the brakes could have been released during the engine start sequence.