Sub-ideal Autorotation in Rotorcraft
Autorotation in helicopters is rarely ideal, with net rotor torque = 0, because some energy is drained from the turning blades to feed the tail rotor.
There's, however, a continuum between the ideal 'autorotation' and the 'windmill brake state/moulinet frein'. The 'point of ideal autorotation' should be taken as the 'point of minimum'. For any increase of the load (the weight of the gyro, for instance), from that point on, there's a multitude of possible equilibrium points in autorotation along that curve of 'windmill brake state'. Real-word autorotation is always in one of those points, and never at the 'point of ideal autorotation'...  You may find useful this illustration and text. Source included.