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Does G3X alert when its ADAHRS and the G5 ADAHRS disagree?

3 ADAHRS

I found this but not much from Garmin on why (below) Seems the G3X should have the ability to lock out a third and give you a warning that "ADAHRS #x disagrees with other 2 ADAHRS by x%. X% could be user settable. I'm still going to have a G5 since it seems fairly independent with the rest of the avionics interface. I don't plan on using a different producer of this type of back-up as it seems not much to gain and another manufactures instrument to learn.

Yes but even if we had 3 GSU25's installed which the G3X will support, to my understanding (G3X team please correct me if I'm wrong), we still wouldn't have a system capable of figuring out which ADAHRS doesn't match the other two and lock that bad unit out, it's still up to the pilot to do the comparison and decide which ADAHRS is not performing correctly and then manually select the right one. A 'miscomp" message only tells you that you that they don't match and you need to look at it and figure it out yourself.

__________________
Walt Aronow, Dallas, TX (52F) RV7A, IO370, C/S, 1500+hrs
 
I found this but not much from Garmin on why (below) Seems the G3X should have the ability to lock out a third and give you a warning that "ADAHRS #x disagrees with other 2 ADAHRS by x%. X% could be user settable. I'm still going to have a G5 since it seems fairly independent with the rest of the avionics interface. I don't plan on using a different producer of this type of back-up as it seems not much to gain and another manufactures instrument to learn.

Yes but even if we had 3 GSU25's installed which the G3X will support, to my understanding (G3X team please correct me if I'm wrong), we still wouldn't have a system capable of figuring out which ADAHRS doesn't match the other two and lock that bad unit out, it's still up to the pilot to do the comparison and decide which ADAHRS is not performing correctly and then manually select the right one. A 'miscomp" message only tells you that you that they don't match and you need to look at it and figure it out yourself.

While they technically could do that, my suspicion is that it is their lawyers that are preventing it from happening. When it comes to mismatches between totally different ADAHRS hardware like the G5 and the GSU25's, there are some technical challenges that might make comparing them a little bit difficult. These things appear simple to the end user but the reality is that they are incredibly complex.
 
3 ADAHRS in G3X Touch

As I understand it the G3X has the capability to handle 3 ADAHRS's in their set-up without involving the G5. This gives the ability to handle these in the same environment. I might be incorrect on this and if a Garmin export could answer this would be great.
 
ADHRS vibration

Can someone give a link what the modification is for the 12. I know the units are vibration sensitive but it seems difficult to find an area vibration free. For my 2 cylinder airframe I mounted a AHRS between the seat and control stick. Seems that was the best spot for that airframe to minimize vibration. Thanks
 
As I understand it the G3X has the capability to handle 3 ADAHRS's in their set-up without involving the G5. This gives the ability to handle these in the same environment. I might be incorrect on this and if a Garmin export could answer this would be great.

With multiple GSU 25 ADAHRS units, you will get a miscompare CAS message if two attitude sources disagree. If we know one source is wrong, it will get a Red X and the system will automatically transition to using the other source.

In the rare scenario where you would have 3 GSU 25 units and one of them where to malfunction in a way that it shows misleading attitude, but the system doesn't flag the output as invalid, it would be theoretically possible to make a determination of which one is wrong. However, the system wasn't designed to do that. The pilot should be able to take all of the data (including from other instruments that my not be in the G3X System) and make a determination of which is correct.

Thanks,
Levi Self
 
With multiple GSU 25 ADAHRS units, you will get a miscompare CAS message if two attitude sources disagree. If we know one source is wrong, it will get a Red X and the system will automatically transition to using the other source.

In the rare scenario where you would have 3 GSU 25 units and one of them where to malfunction in a way that it shows misleading attitude, but the system doesn't flag the output as invalid, it would be theoretically possible to make a determination of which one is wrong. However, the system wasn't designed to do that. The pilot should be able to take all of the data (including from other instruments that my not be in the G3X System) and make a determination of which is correct.

Thanks,
Levi Self

Dear Lavi: Is it possible to plan a new G3X Installation without the GS25 ADHARS ? I already have 2 G5's installed and both witll provide air data and attitude to the CAN BUS for the new G3X display. In this case I will have a redundancy because of the 2 G5's. Is there anything in the GS25 different than the data sent by the G5 to the G3x ??
Thanks,
Maximo.
 
Dear Levi: Is it possible to plan a new G3X Installation without the GS25 ADHARS ? I already have 2 G5's installed and both witll provide air data and attitude to the CAN BUS for the new G3X display. In this case I will have a redundancy because of the 2 G5's. Is there anything in the GS25 different than the data sent by the G5 to the G3x ??
Thanks,
Maximo.
Hello Maximo,

A G3X/G3X Touch installation needs at least one GSU 25 or the PFD will constantly show it is in reversionary mode using data from the G5 backup flight instrument.

The only way around this is to only add a MFD display to go with your dual G5 installation - and that works fine, but it cannot operate as a PFD.

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Thanks,
Steve
 
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Resuming this old thread, I think I solved the adhars drifting by strenghtening its mount.
Tomorrow I'm going to install a secondary magnetometer, a GMU11, so that if I have to pull the G3X ADAHRS breaker to force the autopilot to use the G5 internal ADAHRS, I will not lose heading (since the GMU22 requires the G3X ADAHRS to work). I still have a few questions on failure scenarios:
1) if the G3X fails, will the G5 and autopilot still use the G3X Adhars and the GMU22 as primary sources?

2) if the answer to 1 was yes, would you recommend to pull the G3X ADAHRS breaker in case of G3X failure, in order to force the G5 and autopilot to feed from completely alterative sources (G5 internal ADAHRS and GMU11), in order to isolate other negative ramifications from the G3X failure?
 
Resuming this old thread, I think I solved the adhars drifting by strenghtening its mount.
Tomorrow I'm going to install a secondary magnetometer, a GMU11, so that if I have to pull the G3X ADAHRS breaker to force the autopilot to use the G5 internal ADAHRS, I will not lose heading (since the GMU22 requires the G3X ADAHRS to work). I still have a few questions on failure scenarios:
1) if the G3X fails, will the G5 and autopilot still use the G3X Adhars and the GMU22 as primary sources?

2) if the answer to 1 was yes, would you recommend to pull the G3X ADAHRS breaker in case of G3X failure, in order to force the G5 and autopilot to feed from completely alterative sources (G5 internal ADAHRS and GMU11), in order to isolate other negative ramifications from the G3X failure?

I don't think the G5 uses the GSU25 attitude data. Garmin has stated that one way to identify an error is to compare the G5 to the G3X attitude. This implies that the G5 is always using it's own ADAHRS data. The G5 would have no value as a backup instrument it if used the same attitude source as teh G3X.

Larry
 
In a G3X Touch system with single GSU 25 (with/without a G5) there is no miscompare monitoring. When a G5 is present, it is the pilot's job to compare the attitude data on the G5 and adjacent PFD and decide which to use. In extreme cases, the single GSU 25 can be powered off and the PFD will then revert to using the G5 provided attitude data.
Thanks,
Steve

I would like to ask G3Xpert if the above statement is still true with last 9.22 software version.
At page 380 of the most recent G3X Touch manual is written: "In a system with a single ADAHRS LRU, selecting "ADAHRS + SFD" will always perform miscompare monitoring between the Standby Flight Display and the ADAHRS".


I would like to also mention partial success, with software 9.22, in having a G5+GMU11 as backup in case of G3X and/or GSU25 and/or GMU22 failure (I still lose transponder and OAT, but can live with that in an emergency).

My primary magnetometer is the standard GMU22, linked to my only GSU25/G3X via RS485. I added a GMU11 to the Can-Bus to work with the G5. The G3X system didn’t automatically recognise the GMU11 presence until I enabled ADAHRS #2 in the G3X LRU Config. There obviously isn’t a second GSU25, but this does then allow Magnetometer #2 to be enabled on the next line of the config page. The GMU11 is now clearly visible, with a green tick, in the Can-Bus diagnostics on the G5. And it works fine to drive my autopilot in HDG mode when I pull the GSU25 (+G3X) breaker.

However, I have now persistent yellow advisories on the GDU for ‘AHARS #2 fail’ and ‘ADC # 2 fail’: it isn’t there a second GSU25 after all!
Disabling ADAHRS #2 (G3X LRU Config) effectively removes the GMU11 and associated heading failover.

Seems I have stumbled across an undocumented ‘work in progress’ feature, maybe?
 
I have now persistent yellow advisories on the GDU for ‘AHARS #2 fail’ and ‘ADC # 2 fail’: it isn’t there a second GSU25 after all!
Disabling ADAHRS #2 (G3X LRU Config) effectively removes the GMU11 and associated heading failover.

Seems I have stumbled across an undocumented ‘work in progress’ feature, maybe?

You answered your own question... it doesn't support having a greater number of magnetometers than ADAHRS units, so by telling it to expect two ADAHRS units you have caused it to show you an error message to tell you that one of them is missing.
 
I know, but the G5 ALSO has an adahrs: maybe the G3X could see that as the second adahrs, instead of deeming the second adahrs just a "virtual adahrs" for the sole purpose of detecting and using the GMU11?
 
Our system has a couple times done the following
Attitude indication on the G3X screens starts to drift showing a bank when straight and level. The G5 remains accurate.

I will get an AHRS REVERT message. Shortly followed by AHRS ALIGN, then everything is back to normal.

My system (dual G3X Touch, single GSU25 ADAHRS, G5) periodically exhibits the exact symptoms described above by Matt - PFD horizon gradually tips, AHRS Revert (with CAS alert) and then realign while G5 remains stable. Interestingly, the autopilot remains engaged throughout with no adverse affect.

I had a similar issue but it only happened on full-power takeoff, discussed in this thread and with my eventual fix posted here.I originally had the unit mounted to Van's old "AHRS mount" mod that consisted of a few thin pieces of metal riveted to the bottom skin of the airframe. That location was experiencing unacceptable vibration, and what fixed it (for me) was mounting it to a chunkier piece of metal, and bracing that mount against more of the airframe. Attitude display is rock solid now. This might not fix your case, but it's something to consider.
 
In a G3X Touch system with dual GSU 25 ADAHRS (with/without a G5), there is indeed miscompare monitoring which will result in an attitude miscompare annunciation should significant differences in pitch/roll/heading occur between the 2 ADAHRS units...

In a G3X Touch system with single GSU 25 (with /without a G5) there is no miscompare monitoring. When a G5 is present, it is the pilot's job to compare the attitude data on the G5 and adjacent PFD and decide which to use...

The above quote is from is from 2018. Am I misinterpreting what's written or has the software been updated to provide miscompare monitoring on a G3X system with a single GSU-25 and a G5?

I just added a G5 to a G3X system with a single GSU-25 (and a GMU-22) and there was indeed an amber "ATT MISCOMP" annunciation on the PFD prior to calibrating the G5's pitch/roll.
 
Miscompare Monitor

The above quote is from is from 2018. Am I misinterpreting what's written or has the software been updated to provide miscompare monitoring on a G3X system with a single GSU-25 and a G5?

I just added a G5 to a G3X system with a single GSU-25 (and a GMU-22) and there was indeed an amber "ATT MISCOMP" annunciation on the PFD prior to calibrating the G5's pitch/roll.

Yes, this change was made in GDU4XX software v8.81. Please reference page 30-156 of the G3X Touch Installation Manual for more information.

If you have any additional questions please feel free to reach out to us directly at [email protected].

Thanks,

Justin
 
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