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A320 autothrust ADIRS source

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A320 autothrust ADIRS source

Old 23rd Nov 2019, 13:18
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Join Date: Nov 2015
Location: Venezuela
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A320 autothrust ADIRS source

Hi,
What is the source of Vc used by the autothrust for the SPEED HOLD function?

As I understand it each FMGC has its own ATHR computer. Two valid ADR are needed for ATHR operation.
I also see that each FAC compares all ADR outputs and decides if any of them are faulty - and then, if its own ADR is faulty, it will switch to ADR 3.

So my question is - will ATHR 1 and ATHR 2, as I suspect, use the Vc output by the respective FAC 1 and FAC 2? This isn't explicitly stated but seems to make the most sense.

Also - if your ADR is operative but generating incorrect data - say your captain's pitot probe is blocked, I presume that overspeed warnings still be generated if valid but incorrect data is being shown?
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Old 24th Nov 2019, 21:27
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Join Date: Nov 2015
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Anyone got any information? Trying to understand if switching the active FMGC by switching the active autopilot could potentially make a difference to the autothrust system; e.g. if one ADIRS was reading a couple knots high but still within a range where it isn't yet being rejected as invalid? I presume the airspeed comparison has at least a small tolerance as air data information tends to have measurement errors due to how the probe works?

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