I also expereinced this clucking sound and found it to be caused by controller mapping. The default “helicoptoer” preset for my Thrustmater TCA Sideside had the z-axis mapped to increment / decrement tail rotor. (Not tail rotor axis.) I have rudder peddals that I’ve mapped to the tail rotor axis and had physically locked the z-axis of my joystick. Unforunately, the Thrustmaster TCA is very “noisy” in that the z-axis was registering unsolicited input, thus causing the rail rotor to hit its hard stop. I cleared the z-axis settings from my controller profile and now the clunking has stopped.