aguadalte:
Just a word to clarify that ISIS doesn't receive "attitude from internal gyros", it receives inputs from ADIRU1 and 3.
The problem, as said earlier, is that ISIS containts are classified. I know it sounds weird but again, no one opens up this box !!
While it is true that it gets inputs from ADIRU 1 and 3, it is also true that
it contains gyros !!
What inputs from ADIRUs ? I have no idea because the Airbus doumentation does not describe this. It could be to compare data, or to receive inputs from AOA and such....
It also is linked to ILS receiver 1 for example as you can display the LOC/GS sacles and diamonds.
As a matter of fact, ISIS needs to "align" its ATTitude on power up, and has an in flight ATT re-initialization button as well.
So the GYRO, Attitude information IS definitely self contained !
It is a BACKUP instrument. We know how to use it, we know what can go wrong with it, we do not know how it works inside !
Do we really need to ? not so sure.
By the way it is powered by BOTH the DC ESS bus
and Hot Bus 1