A320 faulty adr identification

[Jkotows2]

How does one identify that an ADR is faulty?

Does the ISIS use ADR 3?

Thanks

[RUMBEAR]

There is a diagram in FCOM chapter 34 ( ADIRS ) which shows what air data is provided to what computer.

In general the air data from CAPT, FO and STBY probes is processed by an air data module ( ADM ) to "computerise" it before passing to each ADIRU. However the ISIS receives raw data directly from the probes ( not via a ADM or ADIRU ). So if all ADR's are inoperative the ISIS will still provide basic information.

One method to identify a faulty ADR is just to compare ADR 1 ( CAPT PFD ) , ADR 2 ( FO PFD ) or on the EFIS switching panel select ( AIR DATA SWITCH ) CAPT 3 ( now ADR 3 is displayed on CAPT PFD ). If it's not obvious then set a know power and thrust from the QRH and this should result in a know IAS. This should determine which ADR's are showing valid information.

[vilas]

If one ADR is faulty the system will automatically reject it without any intimation to the crew.
So if all ADR's are inoperative the ISIS will still provide basic information. Can you explain what you mean by basic information?

[RUMBEAR]

Hi Vilas,

My understanding is ISIS will still provide IAS, ALT ( as they are receiving raw data directly from the probes. I.e don't require any info from ADIRU ) and attitude info from internal gyros.

Please be kind if you need to correct me :).