G3X Touch w/ Dual ADAHRS?

[kirkbauer]

Does anybody use two ADAHRSs with their G3X Touch system? If so, I'd like to ask a few questions.

Background: in my current RV-10 I have one ADAHRS and one G5. If they ever disagree then I plan to use Foreflight (connected to Sentry) to figure out which is closer to correct. But I'd have to notice that they disagree. In my future RV-10, I like the idea of having two ADAHRSs because I understand that the system can alert you if they disagree. Then I can use the G5 to figure out which is correct. Admittedly a failure mode that produces bad values yet doesn't cause the entire unit to fail seems pretty unlikely.

If you have done this before, here are my questions that I couldn't fully answer by reading the G3X Touch manuals:

1) Does it auto-detect disagreement as I think it does? Have you ever seen this happen?
2) I'm thinking I'd hook each ADAHRS up to a separate static port, but was planning on sharing a single pitot tube and magnetometer -- good idea? Or should I have two pitot tubes?
3) It looks like with two PFDs (pilot, copilot) you can configure each PFD to use a different ADAHRS, but it can fail over. How does that failover work?

 

[mburch]

Background: in my current RV-10 I have one ADAHRS and one G5. If they ever disagree then I plan to use Foreflight (connected to Sentry) to figure out which is closer to correct. But I'd have to notice that they disagree.

You can also enable a configuration option for automatic miscompare monitoring between your single ADAHRS and your G5.

It looks like with two PFDs (pilot, copilot) you can configure each PFD to use a different ADAHRS, but it can fail over. How does that failover work?

There is no configuration, but each display will prefer to use a different ADAHRS source by default. If attitude or airdata from the current source goes away entirely, it will switch automatically to a different source, or you can cause this to happen manually at any time through the user interface.

 

[kirkbauer]

You can also enable a configuration option for automatic miscompare monitoring between your single ADAHRS and your G5.

That's interesting! Is there a triple option -- 2x ADAHRS + 1x G5 where it automatically stops showing one if it doesn't match the other two?

 

[Walt]

I install duel GSU25's and a G5 in 90% of my panel installs. Having 3 sources gives you a tie breaker and maximum redundancy if you need it.

 

[dmattmul]

I'm using Garmin G3X with 2 ADAHRS and a G5. Occasionally I see a MISCOMPARE in the CAS but only lasts for a few seconds and have not had enough time to compare to the G5 to determine who is acting up. I'm convinced that this feature will work and gives me time to troubleshoot the system if required. I don't believe the system has an option to automatically compare the 3 and rule out the offending ADAHRS but Matt knows the system 100 times better than me.

 

[togaflyer]

Nothing wrong with good redundancy but ask yourself what type of flying you will be doing and the capabilities of your airplane. One ADAHRS and a G5 connected in the can bus does everything needed to operate safely. If you feel it’s not enough, add what you need to satisfy your safety needs.

 

[bjdecker]

…and “oh by the way”, the GMC 507 has an AHARS built in; not sure of the fail-over operation within the G3X system tho.

 

[Dad's RV-10]

…and “oh by the way”, the GNC 507 has an AHARS built in; not sure of the fail-over operation within the G3X system tho.

Maybe I'm completely misinterpreting but assuming "GNC-507" is a typo and you meant "GMC-507," the GMC-507 is nothing more than a control panel. It's not an autopilot and it's not a ADAHRS.

It's just a button box that allows manipulation of the autopilot without having to do so directly through the G3X (ie: without touching the screen).

 

[bjdecker]

Maybe I'm completely misinterpreting but assuming "GNC-507" is a typo and you meant "GMC-507," the GMC-507 is nothing more than a control panel. It's not an autopilot and it's not a ADAHRS.

It's just a button box that allows manipulation of the autopilot without having to do so directly through the G3X (ie: without touching the screen).

Yes, GMC 507 -- my typo. corrected in the OP.

The GMC 507 does include an AHARS (not ADHARS) that needs to be calibrated when installed. Review the AU version of the installation manual, specifically page 30-17, "30.4.7.2.1 Yaw Offset and Pitch/Roll Calibration with GMC 507 installed", and page 30-101 "30-8 General Tab, Autopilot Configuration Settings"

 

[Dad's RV-10]

The GMC 507 does include an AHARS (not ADHARS) that needs to be calibrated when installed. Review the AU version of the installation manual, specifically page 30-17, "30.4.7.2.1 Yaw Offset and Pitch/Roll Calibration with GMC 507 installed", and page 30-101 "30-8 General Tab, Autopilot Configuration Settings"

Interesting. Thanks for clarifying. Learning has occured:

 

[iamtheari]

I have a G3X Touch with dual ADHARS, G5, and GMC 507. I tried to enable the Flight Control System Monitors on the GMC 507 (when it was a new feature in late 2021) but I mostly got errors on every flight. Garmin eventually told me that this option is intended more for certified installations and they couldn't help me, so I just turned the feature off.

I haven't experienced miscompares in flight but I know I'll have at least some way to sort out which instruments are lying to me if it happens. The dual G3X Touch ADHARS are supposed to alert to a miscompare between them. I don't think that the G5 miscomparing to the G3X will alert, but I don't think I'm missing much there unless the G5 drifts off on its own, I don't notice it, and then one of the G3X ADHARS fails and I use an inaccurate G5 to break the tie between the two G3X units.

 

[Bavafa]

I have a G3X Touch with dual ADHARS, G5, and GMC 507. I tried to enable the Flight Control System Monitors on the GMC 507 (when it was a new feature in late 2021) but I mostly got errors on every flight. Garmin eventually told me that this option is intended more for certified installations and they couldn't help me, so I just turned the feature off.

I haven't experienced miscompares in flight but I know I'll have at least some way to sort out which instruments are lying to me if it happens. The dual G3X Touch ADHARS are supposed to alert to a miscompare between them. I don't think that the G5 miscomparing to the G3X will alert, but I don't think I'm missing much there unless the G5 drifts off on its own, I don't notice it, and then one of the G3X ADHARS fails and I use an inaccurate G5 to break the tie between the two G3X units.

I have enabled the Flight Control Monitoring on the GMC 507 and have not had any issues with it. I only need to wait a bit after the start up to make sure they are all going thru calibration before I start taxing. If I start taxing right away, I may get the miscomp CAS.

 

[mburch]

I have enabled the Flight Control Monitoring on the GMC 507 and have not had any issues with it. I only need to wait a bit after the start up to make sure they are all going thru calibration before I start taxing. If I start taxing right away, I may get the miscomp CAS.

Just a clarification, that CAS message has nothing to do with your GMC 507. The optional internal monitors in the GMC 507 affect the autopilot only.

 

[Bavafa]

Just a clarification, that CAS message has nothing to do with your GMC 507. The optional internal monitors in the GMC 507 affect the autopilot only.

Maybe but that is contrary to what Garmin support told me when I first encountered this and called for help.

 

[g3xpert]

Maybe but that is contrary to what Garmin support told me when I first encountered this and called for help.

A miscomparison CAS alert is issued when a GSU 25 disagrees with the data generated by another GSU 25, or a G5. The GMC 507 monitors function to disconnect the autopilot if its own internal AHRS disagrees with the AHRS data driving the autopilot. No CAS message is associated with the latter.

I have a G3X Touch with dual ADHARS, G5, and GMC 507. I tried to enable the Flight Control System Monitors on the GMC 507 (when it was a new feature in late 2021) but I mostly got errors on every flight. Garmin eventually told me that this option is intended more for certified installations and they couldn't help me, so I just turned the feature off.

I haven't experienced miscompares in flight but I know I'll have at least some way to sort out which instruments are lying to me if it happens. The dual G3X Touch ADHARS are supposed to alert to a miscompare between them. I don't think that the G5 miscomparing to the G3X will alert, but I don't think I'm missing much there unless the G5 drifts off on its own, I don't notice it, and then one of the G3X ADHARS fails and I use an inaccurate G5 to break the tie between the two G3X units.

If the Miscompare Monitor setting is enabled, the system will alert you to a disagreement between the GSU 25 and G5.

I apologize for the miscommunication on our part. AFCS Monitors are definitely not a certified oriented set of features. They are especially useful in an installation in which a single GSU 25 is the only source of ADAHRS information in the aircraft, to disengage the autopilot in the case the system senses a problem. In any other installation, they are still a great set of tools to monitor the system and disengage the autopilot if it senses anything going awry.

If you can reach back out to us we can help determine the cause of the problems you were seeing.



Thanks,

Justin

 

[Richard Connell]

I have a G3X Touch with dual ADHARS, G5, and GMC 507. I tried to enable the Flight Control System Monitors on the GMC 507 (when it was a new feature in late 2021) but I mostly got errors on every flight. Garmin eventually told me that this option is intended more for certified installations and they couldn't help me, so I just turned the feature off.

I haven't experienced miscompares in flight but I know I'll have at least some way to sort out which instruments are lying to me if it happens. The dual G3X Touch ADHARS are supposed to alert to a miscompare between them. I don't think that the G5 miscomparing to the G3X will alert, but I don't think I'm missing much there unless the G5 drifts off on its own, I don't notice it, and then one of the G3X ADHARS fails and I use an inaccurate G5 to break the tie between the two G3X units.

I strongly recommend testing your setup at all sensible combinations of MP and RPM that you are likely to experience, in flight.
Ground testing for vibration IAW the install manual is not sufficient. Nor is it practical or safe at high power settings.
The AHRS are very sensitive to vibration (and noise) and all airframes and GSU locations are different.
Don’t be like me and waste 6m going round in circles before installing the GSUs where Garmin tell you not to…