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I know that this dos not make sense but ever since we upgraded from a legacy g500 to a g500txi to resolve occasional AHRS failures on our PFD (red X, no attitude and autopilot disconnects) things have gone from bad to worse. At random times the AHRS will abruptly fail after working for as much as two hours in flight and then start to have numerous failures. At first Garmin blamed the failures on excess vibration but that really doesn't make sense since the G500txi passes all of its ground tests for electrical interference and vibration on all axes. Also, it is a turbine aircraft and really very smooth compared to any recip. Now Garmin is blaming the avidyne IFD, they say they have seen weird problems when the IFD is integrated with the txi.
Our Garmin dealer wanted me to do a test and remove the IFD and temporarily exchange it for a GNS530W. The results of swapping in the GNS530W are that we had NO failures of any kind on the last two flights whereas I have not been able to make it through one flight without multiple AHRS failures with the IFD.
Avidyne denied that they had ever seen this problem. They now have all the logs and configurations so I'm hoping they come up with something. My only guesses are that there is some software bug on the Garmin side that causes the abrupt failure when there is some drop out or timing difference in the GPS data from the IFD. I never get datalink errors or really any error messages on the IFD throughtout these AHRS failures.
The G500 txi is so dumb that even when it loses its primary AHRS and displays red X over the attitude display it will not automatically switch to the backup (GI-275) AHRS. The pilot has to manually go through a couple of menus to get the AHRS switched.
I love flying with the IFD and the GNS530W is just being used as a bandaid until this is figured out.
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ATP CFI rated pilot
FAA Part 145 repair station owner
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