On A320 there are 3 [ADIRU][1] (ADIRS). ADIRU 1 is shown on Capt display, ADIRU 2 on F/O display. ADIRU 3 can be selected manually. [![enter image description here][2]][2] Each ADIRU contains an air data reference (ADR) and an inertial reference (IR). Each ADR receives the AoA value from a separate AoA probe. [![enter image description here][3]][3] The AoA value is not displayed by default, but it is accessible on the MCDU after selecting the related page. However the values are always used by computers. If values from ADRs disagree, an ELAC can reject the faulty value. A message is displayed, any ADR can be disconnected from the overhead panel. From [this report][4]: > If one ADR has been detected as being faulty, or has been rejected by the flight control computers, and there is an airspeed or angle of attack disagreement between the remaining two ADRs, then a level 2 alert is raised. This activates the master caution and presents an amber NAV ADR DISAGREE message on the ECAM. [![enter image description here][5]][5] The way the discrepancies are managed can lead to rejecting a good value because the two other are wrong, but agree. --- All pictures are from the report. [1]: http://www.a320dp.com/A320_DP/nav-flight-management/sys-14.15.0.html [2]: https://i.sstatic.net/LH3TB.png [3]: https://i.sstatic.net/95glH.png [4]: https://www.atsb.gov.au/media/5776530/ao-2015-107_final.pdf [5]: https://i.sstatic.net/wvBFd.png