What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Heading Error Bug after G3X Software update

rvanstory

Well Known Member
Trying to determine if anyone else is experiencing a heading bug "glitch" after updating their G3X touch to V9.0 software. Here's my story.....

Immediately after updating my G3X Touch software to V9.0, I began to experience a yellow heading caution. It seemed random, and temporary, but would happen EVERY flight right after takeoff during turnout, and 2-3 more times during flight. My avionics vendor suggested I recalibrate my GMU11 magnetometer. It did not fix it.

Then, I had a discussion with a fellow RV-10er hangared at my field, and discovered he was experiencing the EXACT same thing! And his problem started right after V9.0 update, just like mine. Garmin tech support suggested same fix, recalibrate the GMU11 magnetometer. Didn't fix his problem either.

We both have G3X touch, GMU 11 magnetometer and G5 backup PDF.

After learning from each other we both decided to revert back to V8.92 software to see if the problem corrected itself. Both of of us still had the problem.

Then after comparing LRU updates, discovered that in the V9.0 update, the G5 updated to V8.0, but the G5 did not revert back to old version when we reverted the rest of the G3X system to V8.92. This made me wonder if the G5 update could be the source of our issue? So, I have now flown 2 flights with G5 turned off, and NO ERRORS. When I land and take back off with G5 turned on, error shows back up.

However, my friend did the exact same thing (revert to V8.92 and fly with G5 turned off) and he is still having the same issue.

So, we are puzzled to say the least.

Question, has anyone else with G3X, GMU11 & G5 had the same issue after latest software revisions? Does anyone have any ideas on how to diagnose the source? It seems too coincidental that we both developed a hardware issue at exactly the same time after updating to V9.0. Looking for clues.

Screen shots are included of the caution messages we are experiencing.
 

Attachments

  • Heading Error Video Capture.jpg
    Heading Error Video Capture.jpg
    143.5 KB · Views: 202
  • IMG_4186.jpg
    IMG_4186.jpg
    431.4 KB · Views: 241
  • 123_1.jpeg
    123_1.jpeg
    679.2 KB · Views: 168
Last edited:
Randy,

Tell us more about your system. You say "We both have G3X touch, GMU 11 magnetometer and G5 backup PDF.", but you don't say if you have 1 or 2 GSU 25 ADAHRS units.

I suspect you have a single GSU 25 plus a G5, and the miscompare monitoring is occurring between these two units.

Since each ADAHRS unit takes the heading data from your single GMU 11 magnetometer and independently calculates heading at all attitudes, a disconnect in the pitch/roll offset calibration between the GSU 25 and the G5 might be a factor here.

You might try a flight with all of your equipment turned on, but go into the PFD configuration and disable miscompare monitoring between the G5 and GSU 25 and see if that stops the HDG MISCOMP error. It won't get rid of the magnetic anomaly error (airframe interference), but will be a starting point.

MiscompareMonitoring.png

Steve
 
Randy,

Tell us more about your system. You say "We both have G3X touch, GMU 11 magnetometer and G5 backup PDF.", but you don't say if you have 1 or 2 GSU 25 ADAHRS units.

You might try a flight with all of your equipment turned on, but go into the PFD configuration and disable miscompare monitoring between the G5 and GSU 25 and see if that stops the HDG MISCOMP error. It won't get rid of the magnetic anomaly error (airframe interference), but will be a starting point.

Steve

Thank you for the quick response Steve!! We both have single GSU 25's in our systems. I'll try turning off the miscompare monitoring to see what happens. Would you suggest I go back to V9.0 and do this? (or keep V8.92 for now?)

Also may be helpful to know both of us have not had any problems with our setup for over a year. I have 257 hours, he has 300 hours of trouble free flying. So, if it's magnetic interference, or hardware installation issue, not sure why it'd take so long to show up, or why it only showed up after we installed software updates?

If you want to take the troubleshooting offline, PM me your contact info and we can talk by phone till we figure out the problem. Then we can post the results in case anyone else experiences the same.

Thanks again for your help!
 
Thank you for the quick response Steve!! We both have single GSU 25's in our systems. I'll try turning off the miscompare monitoring to see what happens. Would you suggest I go back to V9.0 and do this? (or keep V8.92 for now?)

Also may be helpful to know both of us have not had any problems with our setup for over a year. I have 257 hours, he has 300 hours of trouble free flying. So, if it's magnetic interference, or hardware installation issue, not sure why it'd take so long to show up, or why it only showed up after we installed software updates?

If you want to take the troubleshooting offline, PM me your contact info and we can talk by phone till we figure out the problem. Then we can post the results in case anyone else experiences the same.

Thanks again for your help!

Hi Randy,

You are welcome.

G3X and G3X Touch systems have provided attitude and heading miscompare monitoring between multiple bolt-down ADAHRS units (GSU 73 and GSU 25) for a great many years.

Miscompare monitoring between a single ADAHRS and a G5 is quite new, and was only introduced in G3X Touch V8.81. Any heading disagreement (especially temporary) between your GSU 25 and G5 might have gone unnoticed up until V8.81.

I would re-install V9.00.

Steve
 
Ok. Will reinstall V9.0 and turn of miscompare to start the process. It'll be Wednesday before I will be able to fly again to test, but will let you know results as soon as I do. Thank you again for the help! Just knowing about the miscompare being something relatively new shed some light on it for me!
 
You might try a flight with all of your equipment turned on, but go into the PFD configuration and disable miscompare monitoring between the G5 and GSU 25 and see if that stops the HDG MISCOMP error.

Steve,

I wasn't able top fly today, but my friend with the identical problem tried your suggestion of turning off the miscompare monitoring in his RV-10 today. He said he flew quite "aggressively" and had NO messages or cautions at all!

I see this as GREAT news. But, now it raises another question in my mind.... Would you consider the problem fixed? Or have we just found a way to "ignore" a heading accuracy issue? Do we need to look deeper into the root cause? Or just be happy and fly on with confidence?
 
Steve,

I wasn't able top fly today, but my friend with the identical problem tried your suggestion of turning off the miscompare monitoring in his RV-10 today. He said he flew quite "aggressively" and had NO messages or cautions at all!

I see this as GREAT news. But, now it raises another question in my mind.... Would you consider the problem fixed? Or have we just found a way to "ignore" a heading accuracy issue? Do we need to look deeper into the root cause? Or just be happy and fly on with confidence?
Randy,

Are you/he seeing a heading difference between the G5 and PFD?

You might try re-doing the pitch/roll offset calibration on both the G5 and GSU 25 (done at the same time without moving plane), and then repeat the magnetometer calibration.

If the pitch/roll calibration is off between the G5 and GSU 25 it can cause a disagreement in the calculated heading for each. The magnetometer doesn't provide heading to each ADAHRS/G5, just the magnetic data these units use to calculate attitude corrected heading.

Steve
 
Randy,

Are you/he seeing a heading difference between the G5 and PFD?

You might try re-doing the pitch/roll offset calibration on both the G5 and GSU 25 (done at the same time without moving plane), and then repeat the magnetometer calibration.

If the pitch/roll calibration is off between the G5 and GSU 25 it can cause a disagreement in the calculated heading for each. The magnetometer doesn't provide heading to each ADAHRS/G5, just the magnetic data these units use to calculate attitude corrected heading.

Steve

Plus one for this suggestion and if you have a GMC 507 autopilot, do all three at the same time.
 
Heading Miscompare

The addition of miscompare monitoring in recent software revisions has exposed conflicting calibrations between the G5 and GSU 25 right out of the gate in a few aircraft. The Heading Miscompare CAS message you are seeing is a direct indication that the two do not agree on magnetic heading by a significant margin. Recalibrate the pitch/roll offset on the G5 and GSU 25, and that issue will clear up. You could opt to turn Miscompare Monitoring off, that will clear the CAS message, but the underlying issue will remain.

You do have a magnetic anomaly message present in the picture provided in the original post. That is a direct indication of interference in the vicinity of the GMU. Is that something you have seen in the past? If not, have you serviced any equipment in the vicinity of the GMU recently?

Thanks,

Justin
 
Last edited:
Thank you for clarifying Justin. I will recalibrate both GSU 25 and G5.

On magnetic interference issue, this is 1st (and only) time I’ve seen this. No changes on airframe at all. ONLY clue I might have is that I did attempt to recalibrate GMU 11. Did magnetic interference test. All tested fine except, if I move rudder pedals to full deflection, rapidly, magnetic interference would spike enough to fail. Smaller or slower rudder movements were fine. GMU 11 placement is same for 18 months. Nothing has changed. Wondering if rudder cables can be getting a magnetic charge in some way through normal usage?

Since this is 1st and only time for message in 257 hours, should I monitor longer before attempting a “fix”?
 
Thank you for clarifying Justin. I will recalibrate both GSU 25 and G5.

On magnetic interference issue, this is 1st (and only) time I’ve seen this. No changes on airframe at all. ONLY clue I might have is that I did attempt to recalibrate GMU 11. Did magnetic interference test. All tested fine except, if I move rudder pedals to full deflection, rapidly, magnetic interference would spike enough to fail. Smaller or slower rudder movements were fine. GMU 11 placement is same for 18 months. Nothing has changed. Wondering if rudder cables can be getting a magnetic charge in some way through normal usage?

Since this is 1st and only time for message in 257 hours, should I monitor longer before attempting a “fix”?
This has nothing to do with disturbing the magnetic field. This is about projecting the 3D magnetic vector onto the horizontal plane to determine heading from the vector. If different units have a different understanding of how much the plane is tilted, they will come up with a different heading.
 
Randy - where is your GMU11 located?

I had similar issues on initial flight testing in my 10. My unit is on a shelf on the bulkhead in the tailcone. One factor I found was the steel rear shoulder harness cables were causing issues, namely during certain configurations they would move around or flex a bit and that seemed to make the magnetometer unhappy.

I ended up buying custom replacements made out of stainless, and reinstalled. After doing that and recalibrating, all of my mismatches went away.
 
I had similar issues on initial flight testing in my 10. My unit is on a shelf on the bulkhead in the tailcone. One factor I found was the steel rear shoulder harness cables were causing issues, namely during certain configurations they would move around or flex a bit and that seemed to make the magnetometer unhappy.

I ended up buying custom replacements made out of stainless, and reinstalled. After doing that and recalibrating, all of my mismatches went away.

Which bulkhead do you have your GMU mounted on?
 
Randy - where is your GMU11 located?

It’s toward back of tail-cone under vertical and horizontal stabilizer fairing. It test perfect here when 1st installed and calibrated. No repairs, additions, subtraction since. Over a year of rock solid (no messages) performance.
 
It’s toward back of tail-cone under vertical and horizontal stabilizer fairing. It test perfect here when 1st installed and calibrated. No repairs, additions, subtraction since. Over a year of rock solid (no messages) performance.

Ok, that location seems unlikely related to the issue I was describing then.

When I was troubleshooting I also moved my GSU25 units around a bit to see how they were impacted. I ended up with them mounted to the rear of the G3X screens as that provided the best performance. The downside being if you take the screens out you have more cables to disconnect and plastic tubing to contend with.
 
The addition of miscompare monitoring in recent software revisions has exposed conflicting calibrations between the G5 and GSU 25 right out of the gate in a few aircraft. The Heading Miscompare CAS message you are seeing is a direct indication that the two do not agree on magnetic heading by a significant margin. Recalibrate the pitch/roll offset on the G5 and GSU 25, and that issue will clear up. You could opt to turn Miscompare Monitoring off, that will clear the CAS message, but the underlying issue will remain.

You do have a magnetic anomaly message present in the picture provided in the original post. That is a direct indication of interference in the vicinity of the GMU. Is that something you have seen in the past? If not, have you serviced any equipment in the vicinity of the GMU recently?

Thanks,

Justin

Happy to report, that re-calibrating both the G3X and the G5 solved the problem. With mis-compare still on, no error messages at all in a very bumpy flight conditions.

Thank you Justin and Steve for not only giving me a "fix" but also helping me understand what changed to make the new problem show up in the first place. The G3X team is simply AWESOME!!
 
Last edited:
Happy to report, that re-calibrating both the G3X and the G5 solved the problem. With mis-compare still on, no error messages at all in a very bumpy flight conditions.

Thank you Justin and Steve and not only giving me a "fix" but also helping me understand what changed to make the new problem show up in the first place. The G3X team is simply AWESOME!!

Yes, thank you very much Justin and Steve! I'm Randy's neighbor with the RV-10 that had the same issue at the same time that's now resolved. The key was the pitch/roll calibration on BOTH the G3X and G5 followed by the magnetometer calibration.
 
GMU Interference

Happy to report, that re-calibrating both the G3X and the G5 solved the problem. With mis-compare still on, no error messages at all in a very bumpy flight conditions.

Thank you Justin and Steve and not only giving me a "fix" but also helping me understand what changed to make the new problem show up in the first place. The G3X team is simply AWESOME!!

Happy to help! It is probably worth exploring the source of the failed magnetic interference test. It sounds like small rudder movements allowed the test to pass, but ultimately you don't want to have to worry about any type of movement of the control cables having an effect on the magnetometer.

We call for the interference test to performed at initial install, but do recommend that it is repeated once a year in case anything changes, like you mentioned.

Thanks,

Justin
 
It is probably worth exploring the source of the failed magnetic interference test. It sounds like small rudder movements allowed the test to pass…

I can have full rudder defections too, if it isn’t done excessively fast. I NEVER move the rudder that fast AND that full at same time. Normal defections seem fine. I feel like the friction in the plastic sleeves may be causing minor magnetization. Is that possible?? Can they be degaussed? How?

Other than completely relocating GMU11 out of tail cone, is there another way to solve this possible issue?
 
Similar Situation with Dual G5 Install

I am having a similar situation with the HSI G5 after installing dual G5s, a GAD29, GAD13, and GMU11 with my existing GNS430 non-WAAS. While flying along I am getting the yellow heading on the HSI and losing wind data. It recovers itself, but does it multiple times per flight. I am wondering if it is a similar issue where recalibrating the pitch and roll as well as calibrating the magnetometer again might fix the issue?

The other question I have is, how can the heading be different on the upper and lower displays if it is being supplied from the same magnetometer via the CANBUS?
 

Attachments

  • IMG_5002 copy.jpg
    IMG_5002 copy.jpg
    365.6 KB · Views: 47
  • IMG_5004 copy.jpg
    IMG_5004 copy.jpg
    414.2 KB · Views: 54
Last edited:
Back
Top