In order to prevent possible failure of ADIRU 3, the flight crew must switch the AIR DATA and the ATT HDG in the following order:
-AIR DATA SWTG …........………..……... CAPT (F/O) ON 3
-ATT HDG SWTG ..…….......…………….. CAPT (F/O) ON 3
Aguadalte,
I think I know what you mean.
There are some differences from the qantas 72 case, though.
They kept at normal law almost to the end of the flight. AF447 switched to alternate law.
I still don't understand why the qantas a/c kept in normal law and at the same time it kept using the faulty IR1/ADR1 data.
In alternate law there is still (it seems) some protection regarding AoA but it can be overriden by the crew.
Anyway if AF447 was wrongly informed about their speed the situation would still be dangerous (I suppose).
Can't be sure about the pitots message... Maybe one pitot was already blocked... I don't know how this problem is detected.... Nothing from the Pitot Heat Computer specification to get any valuable hint.
The aim of the following procedure is to isolate both the IR and ADR when an IR is detected faulty in order to prevent the ADR from providing erroneous data to other aircraft systems.
The faulty IR was IR2... Thus even if ADR2 was still providing wrong data, there would be ADR1 and ADR3 in aggreement.
This is complicated stuff...