Incident Overview
The pilot reported that immediately after touchdown, the aircraft 'darted to the left.' Despite attempts to regain directional control, the aircraft ground looped off the right side of the runway. As it entered the dirt area adjacent to the pavement, the aircraft nosed over onto its back.
Examination Findings
An FAA airworthiness inspector examined the aircraft and found that one of the three bolts securing the left wheel halves together had backed out of its associated lock nut. The protruding bolt head contacted the brake caliper, locking the wheel. The maintenance records showed that the wheel halves were last split approximately two years prior to the accident, during a tire replacement.
Sequence of Events
The backing-out bolt caused the wheel to lock, likely contributing to the loss of directional control. The aircraft departed the runway surface, and the soft dirt terrain led to the nose-over. No further mechanical issues were noted beyond the described bolt failure.