As long as it's turning, the tail rotor never stops producing thrust. It doesn't cavitate or "stall" or whatever. It ALWAYS produces thrust. As long as you fly within limits, the t/r will produce enough thrust to do the job. Now, there can be fluctuations in t/r thrust, yes. But just as you can get out of m/r VRS by sliding the disk sideways, as soon as the inflow to the t/r changes...voila...it's back in business doing what it's supposed to do. If the a/c is going round and round at full left pedal, it's because you're either pulling too much torque (over maximum permissable), or you've allowed your m/r and t/r rpm to droop and you've lost thrust. Either way, a crash is imminent. Getting into such a predicament and then blaming the aircraft is the mark of a very poor pilot.