What happened
During the landing roll of a tailwheel equipped airplane, the pilot reported that the initial touchdown was normal. However, shortly after touching down, the aircraft began to drift toward the right. In an attempt to correct the drift, the pilot applied left rudder input, but the deviation continued.
As the pilot applied additional left rudder, a violent tailwheel shimmy developed. The pilot attempted to reduce the load on the tailwheel by reducing aft elevator control, but the shimmy intensified to the point where the pilot had difficulty maintaining pressure on the rudder pedals. Following a loud bang, the aircraft made a sudden turn to the left and entered a ground loop, eventually coming to rest in an upright position. The occupants were not injured.
The investigation
A Federal Aviation Administration inspector examined the aircraft following the event. The inspection revealed that the tailwheel failed at its mounting area. Despite the structural failure of the mount, the control cables remained attached to their respective steering horns.