When a Safety Washer Is Unsafe in a Tail Rotor Hub Assembly

During flight of a Model 47D1, a student pilot reportedly felt a vibration in the anti-torque pedals.  While making a precautionary landing, a loud noise was heard and the aircraft started to spin to the right and landed hard.  Later inspection revealed a tail rotor pitch link bolt fractured with half of the bolt missing.  The remaining pitch link bolt was loose and was equipped with a custom-made safety washer not specified in the parts manual.  The failure mode of the fractured pitch link bolt will be discussed as well as the remaining loose pitch link bolt and its impact on the investigation.