Comment by RealityVoid

Since the new versions of the same ADIRU have EDAC, they have been using it on planes since 2002 and they have been putting the EDAC variant in whenever an old one was being returned for repairs, I don't think this is the reason. I think the reason is that they had 3 ADIRU's and even if one got wonky, the algorithm on the ELAC flight computer would have to take the correct decision. It did not take the correct decision. The ELAC is the one being updated in this case.