When HX is driving TT AP it constantly banks left and right

[BillinDurham]

I have 1,000 hours on this installation of (3) HX systems and a TT AP in an RV10. This problem occurred sporadically in the past and is only noticeable in calm air. Now it's a constant problem in calm air.

When HX is driving TT AP it constantly banks left and right. It seems to be hunting for the exact track and ends up deviating a degree or 2 left and right for the duration of the flilght in calm air. This occurs whenever the TT is in LS or NAV mode. To mitigate the problem, I allow the HX to get the AP on course and at the right altitude, then switch the AP into 'native mode' where it navigates using its internal guidance. The immediately stops the banking.

I've played with some of the HX settings but need some advice. Please help

[GRT_Jeff]

The "NAV" mode usually means the native serial GPS flight plan mode of the TT. Do you mean it works in the serial GPS flight plan mode but not when using the ARINC-429 steering?

There could be some data that's moving around a little, like the magnetic heading, due to noise or interference. We might need a DEMO recording of the behavior to see if we can find the cause.

[Bobturner]

Have you tried reducing the roll gain? This sounds like a settings issue. I have a Trio and it is rock solid, but it probably uses different settings than the TruTrak.

[BillinDurham]

I have played with the HX steering gain but not recently. I'll try some extremes and see what I get.

Regarding the various modes:
There is 'full function 2 axis HX driven mode' where the TT AP displays "EXT LS GS". I assume that is ARINC driven and it is full GPSS steering mode.

There is 'steering-only mode' where the TT AP displayd "NAV". The HX is still driving it but only lateral steering and not GPSS steering mode. That is, it flies to and over waypoints rather than anticipaing them. I'm guessing that it is a serial feed.

In both of the above modes, I get the wing rocking.

There is 'TT native mode" where the AP flies whatever track and climb/descent rate I select. No wing wagging here.

I did get an HX recording and some camera shots but having some trouble finding and organizing them so I'll do that again. Any suggestions on exactly what to do are welcome.