When HX (now HXr) is driving TT AP it constantly wing rocks

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Re: When HX (now HXr) is driving TT AP it constantly wing ro

Post by BillinDurham »

UPDATE: The wing rocking problem has been solved!
SUMMARY: The wing rocking that only occurs when the TT AP is being driven by the GRT HX or HXr EFIS, can be eliminated by increasing 2 settings within the TT AP unit:

1) LATERAL ACTIVITY =5 (or greater)

2) MICRO ACTIVITY =10 (currently testing settings of between 5 and 10).

These settings on the TT do not appear to have any effect on it's performance when being driven directly by the G430w or when operating in standalone mode.

This configuration in my RV10 has been installed and operated since Oct 2011. I don't recall the wing rocking during the first few years but it may have been there from the very start. I do recall trying various mitigation actions such as switching the AP on and off, tuning various settings on the HX and later the HXr, tapping the stick, manipulating the rudder, etc. The installation was inspected looking for play in the control circuit and bearings on the servo (none was detected). However I never tried modifying the settings in the TT AP unit because the wing rocking only occurred with the GRT unit was driving it. And it was independent of Navigation/GPSS mode or Heading mode. The rocking did not occur when it was driven my the G430 or when the TT was running standalone.

The GRT unit appeared to be the culprit. When comparing the TT AP performance when connected to the GRT versus when it was connected to the G430w, it seemed clear something different was going on with the GRT. I was led to understand that the GRT simply passed thru the 'roll' commands from the G430 to the TT AP, and did so without modification. However, GRTJeff pointed out that a bit more was going on:

"NAV mode sends the roll commands, unmodified, from the 430W to the TT. Gains would not affect it. If it wing rocks in that mode then it must be some other data besides the roll command that's causing it. When the TT gets data directly from the 430W, it gets two sets of data, the cross track data and the roll command. The EFIS only sends the roll command. The EFIS also sends the current roll and heading, which the TT could be using to adjust itself."

There wasn't much I could do with that information except to rely on GRT or TT to provide some guidance, advice, or modifications. I was slow to actually take a look at the TT AP unit's settings. Reading the manual suggested wing rocking could be effected by the MICRO ACTIVITY setting. Well, it took some playing with both the LATERAL ACTIVITY and MICRO ACTIVITY settings but in the end, the settings described above in the Summary eliminated the wing rocking.


Thanks to all that engaged with me on this issue, especially Bob "I have a Trio but..." Turner for getting me to look at the TT manual, Dave "worn servo bearings can cause it" Saylor for getting me to give the servo a thorough inspection, and Jeff "it's the same but different" DeFouw for GRT Support.
Bill Watson
8NC8 Durham, NC
RV10 HX, G430w, NavWorx, EIS
Posts: 432
Joined: Mon Mar 11, 2013 6:34 pm

Re: When HX (now HXr) is driving TT AP it constantly wing ro

Post by Bobturner »

Glad you tracked it down, Bill.
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