Firstly - I CANNOT begin to imagine a scenario where the whole system fails inc redundancy...
Fine if by fix you mean jury rig but as one old salt to another, for your own saftey please "imagine it" because it does happen and my previous post about space shuttles was to emphasize the point that modern systems are not designed to fail safe in as much as they dont leave the user with a workable senario and most often are they not repairable by mere mortals even those with knowledge and a box of tools.
Name any component and its failed at some time - hell, I even had a case of a vhf mike that distorted in the sun and rendered the coms system useless (that fault took some findinmg I can tell you) but we arranged flag and light signals with port control should it happen again (redundancy from Nelson!) - the list is endless . . . . DECCA what a joy that was - never really sure it was working and at dusk we went supersonic!