DFC90/DFC100 Digital Autopilot - DFC90 & Turn Coordinator Required

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DFC90 & Turn Coordinator Required

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=1224
Printed Date: 26 Mar 2026 at 3:21pm
Software Version: Web Wiz Forums 12.07 - https://www.webwizforums.com

Topic: DFC90 & Turn Coordinator Required

Posted By: GridFlyer
Subject: DFC90 & Turn Coordinator Required
Date Posted: 13 Feb 2017 at 2:47pm

So I now have the full suite of 3 Aspen Evolution panels, as well as a DFC90 in my Cirrus SR20. The DFC90 uses the input from the Aspen's AHRS for its turn coordination sensing. Well, it turns out that the old six-pack turn coordinator still needs to be hidden under the panel so the DFC90 can feel confident in itself even though it is using a much more accurate unit (AHRS) as the primary input. A six-pack turn coordinator is sloppy by its inherent design function.

Why, Avidyne Engineers, do you set us for yet another maintenance item ($$$$) because the DFC90 is not getting a warm and fuzzy between the AHRS sensing and old technology?! Unless the old six-pack TC is brand new out of the box, there will likely be AHRS MISCOMP error messages produced.

Any plans on getting rid of this requirement?

Replies:

Posted By: Ibraham
Date Posted: 13 Feb 2017 at 4:29pm

I believe it was part of the STC. We just had our TC replaced (it was 11 years old). The best place to get a replacement is Pacific Southwest instruments.

http://www.psilabs.com/

Posted By: AviSimpson
Date Posted: 15 Feb 2017 at 4:56am

What is the software level of your DFC90? We released a service bulletin (part number 601-00170-014) in May of 2014 that removed the requirement for TC. Your installer should have access to this service bulletin.

-------------
Simpson Bennett
Avidyne Corporation
Product Manager

Posted By: Ibraham
Date Posted: 15 Feb 2017 at 5:21am

We had the installation done in October 2016. I will have to check with the installer. I remember asking the installer to mount the Skytrax 100 in place of the TC, and he insisted the TC needs to stay as part of the installation.

Posted By: GridFlyer
Date Posted: 15 Feb 2017 at 5:38am

Release 2 as the DFC90 does not disconnect. However, it was the installers understanding that Cirrus aircraft still needed to TC compare. Not true?

Posted By: GridFlyer
Date Posted: 15 Feb 2017 at 10:28am

Sure that is the correct and/or still active SB number? I can't find it.

Posted By: AviSimpson
Date Posted: 15 Feb 2017 at 10:31am

Yes, still true. The SB is available through the installer/dealer.

-------------
Simpson Bennett
Avidyne Corporation
Product Manager

Posted By: Ibraham
Date Posted: 15 Feb 2017 at 11:05am

This is the response I got from the installer:

"Funny, Avidyne tech reps did not know that. I got into a bit of a disagreement with them over why it was required when we did the installation."

"It may be that in 2014 they changed the way the failure affects the autopilot operation. In that you can continue to operate the autopilot, but the installation data still requires the TC to be there."

Still not clear from last response, is the TC required in any installation?

Thanks

Ibrahim

Posted By: GridFlyer
Date Posted: 15 Feb 2017 at 11:14am

Per this SB, if the Cirrus aircraft previous to the DFC90 was the STEC-55X, the TC is still required. This SB only applied to aircraft that previous to the DFC90 had the STEC-30 and STEC-50 autopilots.

Posted By: 64BoMan
Date Posted: 21 Feb 2017 at 3:23pm

I am installing the DFC90 into an 64 S35 Bonanza that has an Aspen 1000PFD/MFD unit and an STEC 55 (not 55-X) AP. Is the TC still required in the panel?