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G3X ADAHRS No Alt Comp message

Ezburton

Well Known Member
Patron
I have a dual G3X Touch with dual ADAHRS about 18mo since install. I just started get this message (at all times, on ground, in air, etc). There isn't a lot in the Garmin manuals that I have found other than it seems to be missing an input.

If I got all 3 comparator warnings then I would think a bus was bad. But just Alt No Comp seems to indicate that Altitude is not making it across the bus and airspeed . attitude are okay. Just pulling a breaker gets me all 3 no compares and a fail.

I don't know how to debug this. Anyone seen this before or have an idea how to troubleshoot?

Thanks,
 
Pressure Calibration...

The G3X Install Manual describes a Static Pressure Calibration procedure -- see section 35.4.7.4.

Also, In the System Information Page - does each AHRS show up with a green check? Drill down into each sub-menu and see what, if anything, is different or odd between each AHRS...

And lastly, I think there have been a few software updates in the past 18 months...Are you running with the latest/greatest revision?

The aforementioned items is where I would start to debug this...
 
The G3X Install Manual describes a Static Pressure Calibration procedure -- see section 35.4.7.4.

Also, In the System Information Page - does each AHRS show up with a green check? Drill down into each sub-menu and see what, if anything, is different or odd between each AHRS...

And lastly, I think there have been a few software updates in the past 18 months...Are you running with the latest/greatest revision?

The aforementioned items is where I would start to debug this...

The very first thing in the ADAHRS Stitic Pressure Calibration procedure is that this should be done only if you fail a pitot static test and that this is rare and will probably never be used. The way I understood the error message is that its not ABLE to compare #1 & #2, not that they are out of spec different, which would generate at MISCOMP message (Section 10.5 in the pilot's guide).

I didn't look at the Info page... I'll do that. The other functions compare fine (Att, HDG, IAS), so I assumed that the box is working and plumbed to the bus. I think there was a way to always fly with pilot on #1 and copilot on #2. That might at least show which ADAHRS unit has malfunctioned.

I forgot to mention that all the software is up to date.

Thanks for the input.

(My big concern is that the 2 year warranty is up in 2 weeks! So I need to figure out if the unit needs to go back to Garmin.)
 
The very first thing in the ADAHRS Stitic Pressure Calibration procedure is that this should be done only if you fail a pitot static test and that this is rare and will probably never be used. The way I understood the error message is that its not ABLE to compare #1 & #2, not that they are out of spec different, which would generate at MISCOMP message (Section 10.5 in the pilot's guide).

I didn't look at the Info page... I'll do that. The other functions compare fine (Att, HDG, IAS), so I assumed that the box is working and plumbed to the bus. I think there was a way to always fly with pilot on #1 and copilot on #2. That might at least show which ADAHRS unit has malfunctioned.

I forgot to mention that all the software is up to date.

Thanks for the input.

(My big concern is that the 2 year warranty is up in 2 weeks! So I need to figure out if the unit needs to go back to Garmin.)

No Comp generally means there is data missing. It sounds like you have 2 GDU's. Can you put an SD Card in both GDU's and take a short test flight? The PFD will log AHRS 1 and the MFD will log AHRS 2. We can compare the status and data from each AHRS to get an idea of what is going on. Don't worry too much about the warranty date, we generally try to be pretty reasonable with these kind of things.

Thanks,

Justin
 
No Comp generally means there is data missing. It sounds like you have 2 GDU's. Can you put an SD Card in both GDU's and take a short test flight? The PFD will log AHRS 1 and the MFD will log AHRS 2. We can compare the status and data from each AHRS to get an idea of what is going on. Don't worry too much about the warranty date, we generally try to be pretty reasonable with these kind of things.

Thanks,

Justin

I dumped data on GDU 1 but not on GDU 2. I'll have to dump that on my next time down at the airport (Saturday).

I was trying to recall how to manually select ADAHRS 1 or 2, but it didn't jump out at me. I was more concerned with an engine issue over the last few weeks and have ignored this avionics squawk.

Thanks,
 
I dumped data on GDU 1 but not on GDU 2. I'll have to dump that on my next time down at the airport (Saturday).

I was trying to recall how to manually select ADAHRS 1 or 2, but it didn't jump out at me. I was more concerned with an engine issue over the last few weeks and have ignored this avionics squawk.

Thanks,

Just touch the HSI and select.
 
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