Primary finding
Probable cause
The pilot’s failure to turn off the magneto switch before repositioning the propeller by hand which resulted in an inadvertent engine start.
Investigator assessment
Analysis narrative
After refueling the airplane, the engine failed to start after two attempts, and the pilot elected to reposition the propeller by hand. The magneto switch was left in the ON position, and the engine inadvertently started which resulted in a serious injury to the pilot’s arm. The unoccupied airplane then collided with a large metal sign and came to rest upright. The pilot reported that there were no preaccident mechanical failures or malfunctions with the airplane that would have precluded normal operation.