Redundancy in helicopter systems is to bring you safe to the landing spot while failure occurs airborne, not to allow you to take off... Unless it is, as already said, in the MEL or an option that is not included in the type certificate you fly.
Last is the fact that any equipment not serviceable shall be mentioned in the logbook and shall get an appropriate answer before next flight...
My 2 cents from engineer background
Cheers
Kami