If you require a driven tail rotor for auto-rotation, the main gear hub must be fitted with a freewheel; the freewheel on the main rotor shaft then needs to be replaced by a fixed hub mounted on the main rotor shaft.
Main gearbox incl. freewheel for driven tail rotor for auto-rotation landings; kit-form. The pinion shaft 41/25 supplied is only suitable for use with the freewheel bell 36/40 or the hub bell 36/45.