Unreliable airspeed and 2 ADR off
 

Hi guys,
In Unreliable airspeed checklist, under "Affected ADR identification" process there is a line that mentions to keep one ADR on. I understand that in the older checklist one ADR was kept on to maintain STALL WARNING protection. However, after the modification one ADR is kept on to prevent the flight control laws from using two coherent but unreliable ADR data. So, what data will flight control law use from the remaining ADR?

CMpilot1, if you are referring to an Airbus 320, 330/340, see Airbus WIN: https://www.airbus-win.com/wp-conten...ircraft_en.mp4

This may help.

CMpilot1
I think you are talking about irreversible BUSS.When two ADRs are showing same value but wrong they will use that as correct rejecting the third and ELAC will use it to keep normal law erroneously. But since here all are faulty you switch off any two and aircraft will go in alternate law. The only data used is AoA for stall warning. The third is not switched off hoping for ice melting and recovery at lower altitude. But if it doesn't happen then the third is also switched off to get the BUSS which cannot be reversed.

Vilas,
Even in the aircraft that doesn't have BUSS has the same procedure as the one equipped with the BUSS
https://cimg4.ibsrv.net/gimg/pprune....be21a15523.png
The above is the procedure of the aircraft that doesn't have BUSS.


https://cimg6.ibsrv.net/gimg/pprune....d1598bbd7e.png

The above is the procedure listed in 2014 FCOM. If you compare the old one and the new one, you will notice that the info about STALL warning protection is removed. You must be aware that a modification has been carried out routing the AoA through IR instead of ADR enabling STALL warning even with all ADRs off. So, I don't think keeping one ADR on is to provide STALL warning. For melting of the ice.....ok...maybe..

Thank you safety pee. I have already watched this one.

Yes, I remember I think they did that before BUSS. So that if all three ADRs unreliable they can be switched off. Stall warning will come through IR anyway.