Originally Posted by
7-cylinder man
If, before a failure of an IRU, both pilots had been operating using the same source, they would have had clear indication(s) of that.
A basic skill for any pilot is to be able to identify discrepancies between displayed information and to interpret the cause. It really isn't that difficult, but it does often seem to me that it is becoming a lost skill.
7-cylinder man,
I agree that it really isn't difficult, but only if you get to practice it once in a while. And since it isn't practiced much today, along with basic manual flying skills, those skills are lost.