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Notar How it works
It should really be called No
Visible Tail Rotor. Contrary to popular belief there is still a tail rotor and tail rotor gearbox and driveshaft etc. and in addition a composite tailboom with slots in it and a controllable thruster and controllable vertical fins and control cables and bellcranks and sector gears and bearings and.....................................................blah blah blah.
In autorotation the "autorotative driving section" of the disk which is making the blades rotate is in the inner part of the disk. The section of the disk that is providing "lift" (although not enough to sustain level flight but more than no lift at all i.e. glide) is in the outer part. Therefore the inner and outer part of the blade being connected there are no forces going through the transmission so there is very little torque reaction. The torque reaction that remains is in the opposite direction to powered flight as it is required to overcome friction in the main and tail rotor transmission, freewheel drag, swashplate bearing, mast bearing, still rotating fan etc etc. These items are all still using energy which is now only available from the main rotor.
A little quirk of the Notar is when you increase collective pitch on touchdown during autoration you will get antitorque from the Coanda effect when you don't really need it. This is a little different from "conventional" helicopters.