What happened
Immediately following touchdown, the aircraft darted to the left. The pilot was unable to regain directional control, resulting in a ground loop that carried the aircraft off the right side of the runway. As the aircraft transitioned into the dirt area adjacent to the runway pavement, it nosed over onto its back.
The investigation
An FAA airworthiness inspector examined the aircraft and identified that one of the three bolts used to secure the left wheel halves together had backed out of its associated lock nut. The resulting protruding bolt head made contact with the brake caliper, which subsequently caused the wheel to lock. A review of maintenance records showed that the wheel halves had last been split approximately two years before the accident for the installation of a new tire.