DFC90/DFC100 Digital Autopilot - Dumb question / clarification w/two IFDs

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Dumb question / clarification w/two IFDs

Printed From: Avidyne
Category: Avidyne General
Forum Name: DFC90/DFC100 Digital Autopilot
Forum Description: Topics on the Avidyne DFC Digital Autopilots
URL: https://avidynelive.com/forum_posts.asp?TID=2657
Printed Date: 26 Mar 2026 at 8:10am
Software Version: Web Wiz Forums 12.07 - https://www.webwizforums.com

Topic: Dumb question / clarification w/two IFDs

Posted By: jimmyz80
Subject: Dumb question / clarification w/two IFDs
Date Posted: 07 Jun 2024 at 1:25pm

I should know this, but I've been flying a lot of other aircraft lately and it's making my systems memory foggy for my own airplane. :)

I have an SR22 G2 with Avidyne PFD/MFD, IFD540 and 440, and DFC90.

Am I correct in saying that DFC90 is not "paired" with a specific IFD? Meaning I can fly a coupled ILS or LPV on either IFD1 or IFD2, as long as the PFD LSK for nav source is set appropriately (GPS1, GPS2, VLOC2, VLOC2)? On a related note, does the DFC90 even have direct connections to IFD1 and IFD2, or does it just get wired up to the PFD and then the PFD "switches" which GPS/VLOC signal is sent over the wire from PFD->DFC90?

I want to say the answer is yes, and the DFC90 pilot guide seems to state this in two parts (WAAS approaches section and ILS approaches section), but I know there are a lot of variations on the wiring for these installs, different, PFD manufacturers, etc. So I figured I'd double check.

I think I've only ever used the DFC90 with GPS1 or VLOC1, so it's definitely my bad for not having experimented with flying approaches on GPS2 or VLOC2. Should everything work 100% the same?

Thanks!

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2006 Cirrus SR22 - IFD540 IFD440 DFC90 AXP322 MLB100

Replies:

Posted By: Gring
Date Posted: 07 Jun 2024 at 3:13pm

yes, the DFC90 will use whatever nav source is selected on the PFD.

Posted By: Mike_vonb
Date Posted: 08 Jun 2024 at 3:57pm

I have a similar dumbish question; when flying a DME arc for an ILS or VOR approach, and I haven’t yet set the final approach course for the navaid whilst flying the arc using the GPS, apart from changing momentarily to HDG mode, switching the LSK to VOR, changing the CRS, then back to GPS source and NAV mode, is there some other way of doing this? It’s not possible to set the final approach course whilst in GPS as this course only relates to a GPS OBS, not a VOR OBS as the course setting is only applicable to the current nav source. But the course is retained for the ‘other’ source so when you switch, the course also switches.

Was wondering if flying the arc in GNSS mode on the DFC90 and selecting the VOR as the Nav source would allow me to do this without using HDG mode?