This has just been put up for sale on a US FB site
There is considerable debate around this practice, and I am not talking about the seller 
@boscomantico
Have you checked/adjusted the G5 roll offset as detailed in 6.3.7.1 of the Garmin G5 Electronic Flight Instrument Part 23 AML STC Installation Manual 190-01112-10?
Did that affect the yaw indicator as well as roll attitude?
Mine looks as if it needs a wee tweak in pitch and roll.
I should add that I did think twice whether a dual G5 installation replacing King HSI and vacuum AH would be worthwhile in what is effectively an airborne farm bike, but after a first 290 nm flight yesterday I can heartily recommend it.
I don’t know about the G5, but I have the Sandel SG102 AHRS and that needs to be mounted accurately along the aircraft axis.
If the mechanical ball is centred on the ground, with the aircraft levelled (there is a procedure in the MM for that) then I would trust the mechanical instrument.
It may seem obvious, but wouldn’t this be simply the difference between a gyro behaviour and an electronic AHRS as used by the G5? Theoretically both should be the same, but given the technology generation differences …
The question about which to believe is certainly the most important. If the answer is the G5, then that begs the question why a TC is still required for a G5 equipped aircraft. Perhaps regulation not keeping up with technology?
Mine does the same, so I’ll be interested to hear if you find a solution.
A question: does anyone know how the „ball“ in the G5 (or any other PFD, for that matter) is calibrated? And how precise that normally is?
As you can see, the ball on the PFD is slightly out to the left, the ball on the goood old TC is slightly out to the right.
In other words: which one to believe more?
CharlieRomeo,
How did you get the expanded HSI option?
Was that a later update . I’m running 6.0
I thought it was only for non-certified versions…
Thanks
@Archer-181 Sorry for the late response, I was away from the aircraft and couldn’t check the G5. You have to manually enable the expanded HSI, see the attached picture. 
This G5 is running software version 6.40, and the probe is installed in the cabin air inlet.
And regarding the heading error: Sounds like an interference problem. Did you follow the interference test procedure according the installation manual? It wants you to move every possible control surface and use any other system according to a schedule, which, after completion, will tell you at wich time the greatest interference occurred. That should give you a pretty good hint at the culprit. Could easily be some control cables moving too close by.
Any magnetic loop can swing a compass (which the fluxgate is) quite a lot.
If the fluxgate is in the wingtip then you need to make sure any loads within the wing, say the pitot heater, and especially anything on the end of it (nav lights etc), are wired with two wires, running close together. Do not use the airframe as the ground return.
If the fluxgate is in the tail section then the same applies. What loads are there? Tail lamp?
The airframe should not be used for the return wire at all, if any significant current is involved during flight (so the starter motor is ok, and indeed the return conductor for that is usually the airframe).
I know the return for the alternator is usually the airframe, which is bad, but it tends to be ok because the fluxgate is nowhere near the alternator circuit. The alternator current does swing the compass above the panel though, quite nicely, as you change the revs and various loads…
