A320 multiple ADR failure

[upontop325]

Hello fellow bus drivers...had a discussion with my FO today about which ADR’s we would shut off in the event of uncommanded pitch down (OEB). As far as I could tell by studying our manual, we would lose the least amount (system wise) by selecting ADR 2 & 3 off. In particular terrain being associated with ADR 1.

Referencing our ABNORMALS section, it specifically mentions that ADR 1 & 3 would result in gear manual extension with no possibility of retraction. He was adamant that ADR 2 & 3 would also have this same result.

just curious if anyone else has a definitive answer to that? I’m not in the sim for another three and a half months...so I can’t go and test it for myself...

[Lantirn]

Nope your FO is wrong
Manual gear extension is required in 1+3

Deciding which ADR will be on is not so important initially as the task is, which is to get out of normal law and considering the PFs PFD indications

As soon as the flight path is recovered you can rethink which ones you will keep for long term use in the subsequent flight and approach

[upontop325]

Thanks, that’s what I thought. I’ve always made a point of briefing that my first choice would be 2+3 unless I already knew 1 was bad,(MEL, etc,) because you’d lose terrain warnings.

[mrdeux]

If you had an uncommanded pitch down, wouldn't you want to get rid of the one that was actually doing the controlling at the time? It shouldn't matter what else you're going to lose, as that would be incidental compared to a pitch down.

[iggy]

1 + 2 off so you can use the switching panel to display air data information on either side, allowing both pilots to have the controls. It helps during app preparation and briefing, and also allows some sort of fatigue management as neither AP nor A/THR would be available for the reminder of the flight.

Gear extension and retraction is available whenever ADR1 or ADR3 are available, show your FO the logic diagram in the FCOM.

[upontop325]

Airbus just says turn two off...as a previous poster mentioned...to force it into alternate law and getting rid of the protections that are driving it down in the first place. You wouldn’t necessarily know right away which one is the culprit until you had a chance to troubleshoot, which you might not have time to do when you’re pointed at terra firma.

Logic diagrams...I have access to AOM 1 and AOM 2...didn’t see any logic diagrams. I wish I had access to Airbus’ source material...but I only have access to my company manuals.

I do like the idea of 1+2 to be able to switch 3 from left to right as needed.

Thanks all for the replies...

[iggy]

https://cimg1.ibsrv.net/gimg/pprune.org-vbulletin/236x214/green_hydraulic_supply_ldg_gear_320_b740c297f24b189e0909b5db 918d4d30e807c8d8.jpg

[Escape Path]

Having a look at the FCOM in Abnormal and Emergency Proc's, the status page for dual ADR failure only shows ADR 1+3 as the only combination that requires a manual gear extension (with subsequent no retraction). While I have always contemplated turning off 2 and 3 in the event of that failure popping up, I have to say I do like iggy's idea of turning 1 and 2 off so we can switch #3 to either side as required. Something to ponder about.

As a side note, turning off 1+2 apparently would leave you without "ATC/XPDR". I imagine it is only the data provided by the ADR's, not the xpdr signal as such?