The pilot, who due to a dead battery, planned on starting his airplane by hand-propping it. After loading his passenger, he set the throttle and the parking brake, but he elected not to tie the airplane down or place chocks in front of its wheels. When he pulled the propeller through, the engine started right up as he intended, but he had placed the throttle in a position that resulted in a higher RPM than he had expected. Due to the high RPM, the parking brake was unable to hold the airplane in position and it therefore started rolling forward with only the passenger inside. Although the pilot attempted to reenter the airplane, he was unable to do so. While the passenger was able to steer the airplane along the taxiway, she did not know how to stop it, and it eventually went through a fence and over an embankment. During the accident sequence both the fuselage and the wings were substantially damaged. According to the pilot, there was no malfunction or anomaly related to the parking brake system or the throttle mechanism.