[tankenmate]

I think the whole point is that in almost all circumstances an ADIRU failure will lead directly or indirectly to alternate law. Hence the correct procedure should be to assume alternate law and cross check.

Once your instruments start failing left, right, and centre you should go into what I call "advanced free fall" mode, check horizon (true, false or otherwise), check altitude, check parachute, repeat... If you hit gimbal lock (or similar INS failure) in the dark, well just bend over and kiss it goodbye.

[einhverfr]

I was thinking of the Qantas and Malaysian Airlines mishaps where faulty ADIRU's lead to sudden uncommanded changes in altitude and eventual stall warnings.