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Air data but no baro alt

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paulr View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paulr Quote  Post ReplyReply Direct Link To This Post Topic: Air data but no baro alt
    Posted: 14 Feb 2024 at 6:54pm
I am probably missing something super simple.

My IFD440 is wired to an Aspen display through an Aspen ACU.

I get the Aspen wind vector block, and I see OAT, IAS, and TAS on the IFD (including on config page 5).

What I *don't* see is baro altitude. More specifically, I still get "manual sequence required" when I fly a missed like the ILS 18 KMDQ, and I don't see B ALT or D ALT data on config page 5.

Any idea what the missing ingredient here is?
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eallevato View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote eallevato Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2024 at 10:37am
That is because it is not wired properly.
In order to get Baro altitude, the ARINC 429 data to the IFD must come from pins 26 and 27 on the EFD itself and not from the ACU.

Gene
Gene
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paulr View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paulr Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2024 at 10:52am
Ouch. Is the ACU stripping that 429 label or something? I didn't see this explicitly called out in the IFD install manual, just a note that the Aspen is an approved airdata source. I need something I can show my installer (who's not an Avidyne dealer, grrr) to get them to fix this properly.
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eallevato View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote eallevato Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2024 at 11:28am
Yes, the ACU strips the Labels out.
See Note 2 on Figure 9-28A on the install manual.

Gene
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paulr View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote paulr Quote  Post ReplyReply Direct Link To This Post Posted: 15 Feb 2024 at 1:06pm
Thanks, Gene! That's exactly what I needed.
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