What happened
During the landing roll, the pilot performed a wheel landing. As the tailwheel made contact with the ground, the aircraft began veering to the left. In an attempt to correct the leftward movement, the pilot applied right rudder and subsequently applied the right brake. Despite these efforts, the aircraft continued its leftward trajectory and entered a ground loop.
The impact caused the right main landing gear to shear off. This was followed by the right wing, right elevator, and right stabilizer making contact with the ground. The pilot was not injured during the event. At the time of the accident, the pilot noted that the winds were calm.
The investigation
An examination of the tailwheel assembly following the accident revealed that the tailwheel-locking collar had not been installed on the tailwheel fork assembly. While the tailwheel-locking bell crank was properly installed and the cockpit controls operated normally, the tailwheel could not be locked without the missing collar. This omission meant the assembly could not prevent uncommanded direction changes.
Additionally, investigators found that the steering notch on the tailwheel steering arm assembly was worn out. This wear allowed the tailwheel to rotate around the steering axis with only minimal manual force, which would permit the tailwheel to swivel without command during a swerve. A review of the aircraft logbooks showed that the last check of the tailwheel occurred during the most recent annual inspection, but there was no record of when the assembly had last been disassembled.