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

PostPosted: Wed Aug 21, 2019 1:44 pm
by BillinDurham
BillinDurham wrote:
Bobturner wrote:Did you try Jeff's suggestion? Let the 430 drive the TT; watch the efis carefully. Does the AI or heading indicator (tape) ever "twitch" (even if the plane is rock-solid level)? I'm really curious as what can be going on here.

I'm missing where Jeff's suggestion made(?) Maybe I misunderstood. I checked and made sure my settings were the same as suggested in his 5/20 post.

But I'll do exactly what you are suggesting here... that makes sense as a next check. I'll record the results as well. Have a long leg coming up on Monday.

Thanks.

Flight completed. I let the G430 drive the TT AP for extended periods of time. As expected, there was no wing rocking. Watching the GRT HXr display during this steady state flight, there were no 'glitches' in heading or track. Nothing to account for the wing rocking that did and will occur anytime I let the GRT HXr drive the TT AP.

I took videos but they add nothing to what I've already posted.

I'm going to post a summary of the basic wing rocking problem and all the actions taken on my part to mitigate the problem. GRT, I need your help here!

Summary of Wing Rocking Problem when HX or HXr is driving TT

PostPosted: Wed Aug 21, 2019 2:38 pm
by BillinDurham
Problem: Whenever the GRT HXr is driving the TruTrak Autopilot, my RV-10 wings rock with a period of approximately 4 seconds. It sickens passengers and is driving this builder/pilot a bit crazy.
- This problem occurs in all GRT AP modes; ENAV, GNAV, and Heading modes.
- It occurs independent of any AP settings in the GRT Setup menus (all have been tried)

The Problem does not occur when the TruTrak Autopilot is driven directly by G430w

> The ARINC connection to the Autopilot is switchable between the GRT and the G430w.
- When switched from GRT to G430w, there is momentary left/right heading adjustment and the wing rocking stops completely.
- When switched back from G430w to GRT, the wing rocking resumes.
- - Sometimes it takes 15 or 30 seconds before it reaches full amplitude.
- - Often the wing rocking starts immediately at full amplitude, 4 second period

> The serial connection to the TruTrak is not switchable but it has been rewired as a possible solution
- Originally, there was a serial connection between the G430w and the TruTrak AP
-- When the Trutrak was getting the ARINC from the GRT and the Serial from the G430 - we have wing rocking
- The serial wiring was changed to a connection between the GRT and the Trutrak AP
-- When the Trutrak was getting ARINC and Serial from the GRT - we have wing rocking
-- (When the Trutrak was getting ARINC from the G430w and Serial from the GRT - no wing rocking)

The Problem does not occur when the Trutrak Autopilot is used manually with no external inputs

Documentation of the problem:

- Earlier in this thread and others, videos and demo files have been shared that illustrate most or all of the modes described above
- If additional information is required, let me know.
- At this point I think I've exhausted my testing and data collection options.

Background:

I've been flying this configuration for 9 years and 1100 hours. While I don't recall having this problem originally I cannot document that fact so I can only say this problem has existed for at least several years.

The problem existed with the (3) HX systems I originally bought and with the newer HXr I recently bought.

Presumably this is not a problem with the new GRT AP connected to the HXr, but this was not an option when I purchased or installed my gear.

Please help!

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

PostPosted: Wed Aug 21, 2019 11:50 pm
by Bobturner
I’m stumped. One thing you have different from me (beside the TT vs Trio) is the fast trak hub. Is it possible there’s a wiring error, like A and B swapped? I have no idea what that would do. Or, could there be some sort of 1/2 Hz interference being picked up? One last, non-trivial thing to try, would be to by-pass the hub, run the arinc line directly from the HXr to the TT.

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

PostPosted: Thu Aug 22, 2019 5:12 am
by GRT_Jeff
If the ARINC wires were swapped it wouldn't work. That inverts all the data bits.

If there were a bad or intermittent connection (so it receives less updates than expected) maybe that could cause it but that's not likely. You should see more obvious problems if the connection is bad. I'd expect the response would be more jerky at least.

Greg sent an e-mail to TruTrak to see if they know something else in our ARINC data could be causing it. We send some data that the 430W doesn't, and the 430W sends some data that we don't. If they don't have any ideas we may have to try some experiments with our ARINC output. It's not something that affects every TruTrak installation though, because we have a lot of systems wired to them without reports of wing rocking.

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

PostPosted: Sun Sep 01, 2019 12:49 am
by Bobturner
Bill, did you say (and I miss it) exactly what model TT you have? It's been a while since I was behind a TT, but I thought it displayed "GPSS" in the lower left, when being driven by the GRT. I also seem to recall it had to be in altitude hold (my memory may be failing here) to switch correctly from direct GPS input to GRT input on the ARINC lines.

Here's a post from VAF:
-----------------------------------
I have toggle switch on panel to make the choice, I leave in EFIS.
The HXr will not control the autopilot unless the Trutrak is first in Altitude
Hold mode then switch to the GPSS VS mode.

What I do:
In the EFIS AP I choose HDG, set roll out altitude and climb rate and sync
heading bug.
On climb out I hit the black knob on the AP to turn it on. For TT it will
hold the climb. I then hit the Altitude button then the black knob on the
TT for altitude hold then tap the Mode button until GPSS VS is showing
in the TT window.
As soon as you get to GPSS VS the AP is following the HXr auto pilot commands.
You can then go into HXr AP and choose your AP mode.
------------------------------

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

PostPosted: Tue Sep 03, 2019 4:19 pm
by BillinDurham
I have the DII VSGV; DIGIFLIGHT II VS GPSS V PPROGRAMMER manufactured sometime before 2011.

Normally I have it switched to the GRT HX or HXr. In that mode of operation, all I do is turn the AP on by pressing the black knob. From that point on, I generally don't touch the AP and operate it all modes by presing buttons on the GRT. Except for wing rocking, I can't imagine it working any better than does. Seamless, effortless AP control from just after takeoff to DA is possible.

If I'm in a climb when I turn on the AP, it picks up the climb rate in altitude read-out. In that case I press the altitude button and it goes into VS mode and from that point, I only press buttons on the GRT.

I NEVER switch the AP direct to the G430w... there's not reason to do that. EXCEPT in problem determination mode. It is a simple way to demonstrate that the GPSS steering with zero wing rocking is possible and it tends to point to the GRT as the problem causing wing rocking. However I now often switch to G430w mode which causes a whole set of other challenges requiring more systems management and button pushing.

(all the above is from memory)

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

PostPosted: Thu Sep 05, 2019 5:37 am
by Bobturner
Bill,
I can’t find anything on the TT web site about a ‘Programmer’ model. There is a manual for the Digiflight II VS which agrees with my previous post - that you have to push the mode button until displaying ‘GPSS’ to get it to accept external commands. Yours must be a rare model. Perhaps you can find someone at TT who can tell you if this particular model handled incoming ARINC commands any differently than the standard D II VS models.
BTW, I watched the Utube video. I’d say the wing rock has a 4 sec period - if that makes any difference.
Bob

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

PostPosted: Thu Sep 05, 2019 5:01 pm
by BillinDurham
Bobturner wrote:Bill,
I can’t find anything on the TT web site about a ‘Programmer’ model. There is a manual for the Digiflight II VS which agrees with my previous post - that you have to push the mode button until displaying ‘GPSS’ to get it to accept external commands. Yours must be a rare model. Perhaps you can find someone at TT who can tell you if this particular model handled incoming ARINC commands any differently than the standard D II VS models.
BTW, I watched the Utube video. I’d say the wing rock has a 4 sec period - if that makes any difference.
Bob

The 'Programmer' term is right off the invoice. Not sure what it means but I'm pretty sure it's just the standard Digiflight II VS. I have to push the mode button, once in most circumstances, to get it accept eternal commands. I once demonstrated to a friend how I could hit that button once after takeoff and then fly the plane for the next 2 hours down to final approach without touching anything other than adjusting the power levers and pushing buttons and twisting knobs on the GRT HX.

Agreed, the period is 4 seconds. May need to go back to my physics 103 text.

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

PostPosted: Thu Sep 05, 2019 7:08 pm
by Bobturner
Agreed, great autopilots. I feel the same way about my Trio, except I need to push 2 buttons after takeoff (Trio has separate engage buttons for roll and pitch); push one stick button to disengage both prior to flare.
I don’t see anything like what your display is showing, in the TT digiflight II manual. All the photos in the manual show “GPSS” being displayed on the left side, when being controlled by an efis. Your Utube video is very different. Have you tried pushing mode until gpss appears? Then the alt button to get gpsv?

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

PostPosted: Fri Sep 06, 2019 10:33 pm
by GRT_Jeff
They renamed GPSS and GPSV to EXT L/S And EXT V/S in some newer versions.