ADAHRS voting logic

[KRviator]

G'day gents,

My -9A kit is arriving very shortly, and given its' a QB, I'm starting to give serious consideration to panel planning. This in turn leads me to the Skyview system of 2x D1000's and a D700 in the middle - fed by a VP-X and GNS430.

No problem there, however, the issue I'm concerned about is, by having an ADAHRS-200 and an ADAHRS-201 feeding the network, what happens if/when one disagrees with the other? Does the -200 overrule the -201? And following on from this, is it possible to have the -200 feed one D1000, with the -201 feeding the other?

 

[dynonsupport]

At the moment, there isn't any voting or cross-comparison. Either single ADAHRS will provide all the flight instruments to the whole SkyView system (which ADAHRS is pilot-selectable, and it doesn't change randomly on you). If the active ADAHRS should fail, the other automatically takes over.

A future update will add things like ADAHRS cross-comparison and better redundancy in that vein, but we haven't yet decided the exact mechanisms.

 

[KRviator]

Yet another reason I've chosen Dynon, ask a question on the forum and it's answered within 16 minutes, and well after COB.

Given that only one ADAHRS will feed the network at any one time, at what point does it declare itself "failed" and let the other take over? I'm sure there are some insideous ways to have an AHRS fail, and my concern would be the possibility exists to blindly follow bad info all the way to the ground if it is a subtle failure.

Going by your previous reply, it seems that once plugged into the network, whichever ADAHRS I nominate as the primary is the source of attitude info unless it fails. Is there a way to have one screen accept the -200 data, and the other screen the -201 data, while both accept mapping/engine data?

Apologies for making this confusing, and many thanks for the unexpectedly prompt reply.

 

[Jonas]

I find if I have my autopilot power off, my 2 skyview screens on, then switch the autopilot power on anytime during the flight, my ADAHRS and EMS will momentarily X out, then the ADAHRS will get switched.
(The only reason I notice is because I only installed one OAT sensor, and the cross wind calculation disappears)

If I turn on power to the autopilot before powering up the skyview screens, the ADAHRS will not change.

 

[dynonsupport]

If the ADAHRS is reporting valid data, it's considered working. If it goes away entirely, the system switches. There is some more sophisticated cross-checking that we will be doing in the shorter term future, but the system does not do this yet.

The system is designed to not switch ADAHRSes unless it detects one fail. But as Jonas has found, sometimes turning system components on and off (such as APs and displays) can cause the system to go re-find all of the modules for a moment. This can cause the active ADARHS to switch.