[sneak]

I think backups for the electronic systems would not need the same level of redundancy as the primary systems (which presumably already have backups).

It's sort of like how you don't need RAID for your offsite backup disks, just some parity for bit-rot.

The mechanical instruments would be the (additional) redundancy. The additional weight/lines/service is indeed burdensome even without redundant mechanical systems.

[mlindner]

> I think backups for the electronic systems would not need the same level of redundancy as the primary systems (which presumably already have backups).

If your backup is failing more often than your primary system then it's not much use as a backup.

Also, there ARE backups. There's fallback artificial horizon boxes that work independently of the rest of the system, for example.