Accident Overview
The airplane experienced a ground loop during the landing roll after the pilot performed a wheel landing. As the tailwheel made contact with the runway, the aircraft began veering left. The pilot applied right rudder and then right brake to counter the veer, but the airplane continued leftward, resulting in a ground loop.
Damage
The right main landing gear sheared off, followed by ground impact of the right wing, right elevator, and right stabilizer.
Post-Accident Examination
Examination of the tailwheel assembly revealed that the tailwheel-locking collar had not been installed on the tailwheel fork assembly. The locking collar is designed to prevent uncommanded swerves or aircraft direction changes during takeoff and landing. The absence of the collar was not immediately apparent and only became evident when the tailwheel was disassembled.
The tailwheel locking bell crank, installed on the tailwheel bracket assembly, is designed to engage with the locking collar to lock the tailwheel. In the cockpit, the tailwheel-locking control and the bell crank operated normally; however, without the collar, the tailwheel could not be locked.
Additionally, the steering notch on the tailwheel steering arm assembly, which enables the tailwheel to steer the airplane, was worn. This wear allowed the tailwheel to be turned about the steering axis with only light force applied by hand, potentially allowing the tailwheel to swivel without command during a swerve.
Logbook Review
Review of the airplane's logbooks did not reveal when the tailwheel assembly was last disassembled. The most recent check on the tailwheel was during the last annual inspection.
Environmental Conditions
As the pilot exited the airplane, he noted that the winds were calm.