Accident Overview
The pilot completed two landings. During the second landing, the airplane's main landing gear failed. The pilot subsequently lost control, and the airplane veered off the runway and ground looped.
Aircraft Modification
The airplane had been modified with the installation of conventional leaf spring main gear and a tail wheel assembly.
Post-Accident Examination
A main gear attachment bolt was found partially stripped from its respective nut plate assembly. Only about four threads at the bolt's end were observed stripped, and only a portion of the threads in the nut plate were observed stripped.
Sequence of Events
During the landing, the improperly secured bolt pulled out of the nut plate, leading to the landing gear failure.