I have personal experience that an improperly adjusted tailwheel swivel bearing will cause similar results to the issue this owner was investigating. If the swivel king pin nut is too tight the tailwheel will resist the steering spring as the rudder is deflected. Add a little more rudder pedal force and the tailwheel breaks out causing a sudden rudder movement. It is a very unpleasant control response and one that I knew had to be fixed on the ground before further flight.
In my case the improper adjustment was made in an attempt to eliminate tailwheel shimmy.
Last edited by EXDAC; 16th Apr 2024 at 16:34.