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RV74ME

Well Known Member
Was out doing some light aerobatics today and got an “ATT MISCOMP” message on the G3X. Rolled out wings level and sure enough the GDU and G5 were conflicting. Eventually it corrected itself, but I was curious so did a couple more rolls. Never got the message again, but there did still seem to be some disagreement.

What could cause this? Btw, I recently updated software to 9.21
 
Me too.

I had a similar experience when flying with my friend in his newly minted Lancair ES. The G3X threw a “HGD MISCOMP” caution and the autopilot then lost its mind, turning us off course.

What is all of this MISCOMP business?
 
It is when the AHAR does not agree with other AHAR (G5 or Auto Pilot)
You will need to calibrate them all at the same time to make sure they are all based on the same aircraft attitude.
Another possibility for the MISSCOMP is if one of those LRU were powered up while the aircraft was moving.
 
I had a persistent "ATT MISCOMP" problem happening at high RPM that turned out to be vibration related. If you have a data log from that flight and can send it to the G3Xpert E-mail address, they might be able to help you diagnose it. Where is your GSU ADAHRS unit installed in the plane?
 
Draker said:
I had a persistent "ATT MISCOMP" problem happening at high RPM that turned out to be vibration related. If you have a data log from that flight and can send it to the G3Xpert E-mail address, they might be able to help you diagnose it. Where is your GSU ADAHRS unit installed in the plane?
Click to expand...

I have it mounted on the subpanel, directly behind the GDU.

Been flying it for 4 years and 375 hours with zero issues thus far. Dont believe its a vibration issue
 
To avoid common mode errors, the G5 and the G3X system use different sensors, software, etc -- something like that -- so it's maybe not surprising that they give different indications in the corners of the flight envelope, like, aerobatics.
 
My opinion, if you actually fly in IFR conditions, you should have a tie-breaker.
 
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