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enroute VNAV and TruTrak Vizion autopilot

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pburger View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pburger Quote  Post ReplyReply Direct Link To This Post Topic: enroute VNAV and TruTrak Vizion autopilot
    Posted: 19 Sep 2022 at 8:01pm
When we upgraded the IFD-540 to 10.3, we enabled the enroute VNAV to see what if any functionality we might get.  It definitely sends altitude setpoints to the TruTrak Vizion autopilot. This was a source of a lot of confusion on a recent flight while practicing approaches under the hood.

To try and better understand what was happening, I flew a test flight.  I entered a flight plan and put in crossing altitudes on various legs to see how the system handled it. These altitudes were sent to the TruTrak, but not necessarily immediately- if I changed an altitude on the IFD the altitude on the TT didn’t update immediately, but if I tried to adjust the altitude on the TT it would change to the altitude entered on the IFD- curiously the altitude on the TT was the altitude on the IFD plus one, I.e.- 2000 on the IFD would show up as 2001 on the TT. I could not override the altitude on the TT with a manual entry - it would just immediately overwrite with the value from the IFD. The altitude was being pushed to the TT both in track mode and in GPSS mode. 

I thought maybe this could/would be a new way of operating: Updating the leg altitudes in the IFD, and having the autopilot automatically update and fly those altitudes.  I have concluded that this is a non-starter.  I found it way too confusing, and I felt like I was fighting the system constantly.  I don't want the IFD forcing altitudes to my autopilot when I'm not expecting it.

We disabled enroute VNAV for now.  I doubt we'll enable it.

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R0bst3r View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote R0bst3r Quote  Post ReplyReply Direct Link To This Post Posted: 21 Sep 2022 at 5:08pm
Did disabling enroute VNAV fix your issue?  Enroute vnav was already disabled on my 440 and im seeing the same problem you described, forced altitude +1 ft. 

Edited by R0bst3r - 21 Sep 2022 at 5:08pm
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pburger Quote  Post ReplyReply Direct Link To This Post Posted: 23 Sep 2022 at 2:45pm
Originally posted by R0bst3r R0bst3r wrote:

Did disabling enroute VNAV fix your issue?  Enroute vnav was already disabled on my 440 and im seeing the same problem you described, forced altitude +1 ft. 

Well, I flew one cross-country last weekend after the enroute VNAV was disabled and didn't have any issues with the altitude setting on the A/P.  I didn't input any crossing altitudes, though, so maybe if I did, the problem would show up again.  I hope not.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pburger Quote  Post ReplyReply Direct Link To This Post Posted: 24 Sep 2022 at 12:20am
PROBLEM PERSISTS!!

I have Enroute VNAV Disabled

Flew a test flight this evening.  I set up three legs each with different crossing altitudes.  The crossing altitudes are being sent to the TruTrak a/p as “altitude + 1”.  If the constraint is 1600, 1601 is sent to the autopilot.  This is NEW BEHAVIOR with 10.3.  Prior to 10.3 I routinely set a desired crossing altitude x nm before a waypoint to assist with planning my descent.  I would get the TOD marker and the Boeing banana.  My a/p never automatically changed its altitude set point.  I would put in a target altitude into the a/p and it would not be overwritten by some value being sent from the IFD.

With 10.3 if I use crossing altitudes it sends those to my autopilot.  Why does it do this with Enroute VNAV DISABLED??

Under ‘Main ARINC 429 Config’ I have VNAV set to Enable Labels. This is how it was set up prior to 10.3. I believe the Enable Labels was turned on when the a/p was installed to allow for vertical guidance on approaches.  I’m guessing if I turn off the labels the enroute altitude constraints won’t be sent to the a/p, but then I suspect I will lose vertical guidance on approaches.

Avidyne please review this and chime in here.  What’s going on?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote R0bst3r Quote  Post ReplyReply Direct Link To This Post Posted: 24 Sep 2022 at 9:35pm
I'm seeing the same issues as you with the same config, vnav disabled, labels enabled.  I noticed if there is a constraint anywhere in the flight plan then the autopilot is sticking to it.  For example, on the ground load the approach you want on the IFD, IAF is 2000 ft.  Then set the altitude preselect on the IFD, for example 4000.  Take off.  Guess what, after you take off the IFD is "forcing' the trutrack to 2001.  Only fix is disconnect the autopilot, and either change the IAF to 4000 ft, or another waypoint before it so you get your enroute altitude.  Not cool.

But if you cross that waypoint with the 4000, and say the next waypoint has a constraint for 2000, the trutrak does not change to the new 2000, it does stay at 4000.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pburger Quote  Post ReplyReply Direct Link To This Post Posted: 25 Sep 2022 at 12:55am
Yep, but IIRC, the altitude sometimes does not update automatically, but if you try to adjust the altitude manually it will be overwritten by the next constraint.  It’s super frustrating.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote R0bst3r Quote  Post ReplyReply Direct Link To This Post Posted: 26 Sep 2022 at 3:56pm
We should probably open a support case.  If you haven't already let me know and I will.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pburger Quote  Post ReplyReply Direct Link To This Post Posted: 26 Sep 2022 at 4:01pm
I have not.  Please do.

I may start a thread on here with a comprehensive list of 10.3 bugs, though. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pburger Quote  Post ReplyReply Direct Link To This Post Posted: 27 Oct 2022 at 10:36am
The IFD is sending altitude setpoints over ARINC429 when altitude constraints are present EVEN with enroute VNAV turned off.  

Does Avidyne acknowledge this new and unexpected behavior that started after the upgrade to version 10.3.0.2 is a bug?  If not, can you explain under what circumstances altitude setpoints would/should be sent out over the ARINC429 interface in the enroute portion of a flight when Enroute VNAV is TURNED OFF?
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AviSteve Quote  Post ReplyReply Direct Link To This Post Posted: 05 Nov 2022 at 6:36pm
Personally looking into this one.  What's your configuration?  Do you have an Aspen or a G5?  Is the TruTrak connected directly to the IFD via 429?  What 429 configuration is selected?

If I understand this correctly, you are currently unable to set a selected altitude on the autopilot control panel and have it stick because it keeps getting overwritten by the IFD.  Is that correct?


Edited by AviSteve - 05 Nov 2022 at 6:37pm
Steve Lindsley
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pburger Quote  Post ReplyReply Direct Link To This Post Posted: 05 Nov 2022 at 7:56pm
No Aspen, no G5.  The TruTrak is connected directly to the IFD via 429.  The configuration is shown below.

If an altitude constraint is present on the next waypoint, then that constraint is written to the TruTrak's altitude setpoint(with a 1 added to it).  In that state, if I try to dial in an altitude manually on the TruTrak, it gets overwritten by the constraint +1 immediately.  This did not happen prior to 10.3.  

It does this with Enroute VNAV enabled or disabled.




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Post Options Post Options   Thanks (0) Thanks(0)   Quote AviSteve Quote  Post ReplyReply Direct Link To This Post Posted: 05 Nov 2022 at 10:25pm
Disabling Enroute VNAV disables the function, but the labels continue to be transmitted.  If the outputs are marked as invalid, that shouldn't matter.  But, the selected altitude output is driven by the same variable used to compute VSR, so it's not invalid.  There's the source of the issue.  If the autopilot had a specific VNAV mode, I'm pretty sure sending that label would be irrelevant.  Since TruTrak doesn't, it's clearly looking at it all of the time.

Encoding looks right to me, so I'm not sure why TruTrak would decode it as +1, but that's a minor point.

Whether we call it a bug or an integration issue, the result is the same.  We'll get it fixed ASAP.
Steve Lindsley
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Post Options Post Options   Thanks (0) Thanks(0)   Quote pburger Quote  Post ReplyReply Direct Link To This Post Posted: 06 Nov 2022 at 7:36am
Thanks for acknowledging this.  This and the frequency issue really casts a pall on my IFD experience. Don't get me wrong, I'm still a believer!
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AviSteve Quote  Post ReplyReply Direct Link To This Post Posted: 06 Nov 2022 at 10:36am
I understand and we do appreciate the loyalty.  We're working hard to make it right.
Steve Lindsley
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Post Options Post Options   Thanks (0) Thanks(0)   Quote ricardo Quote  Post ReplyReply Direct Link To This Post Posted: 06 Nov 2022 at 12:26pm
pburger -- 

have you tried disabling the labels and testing whether you still get vertical guidance in an approach.

..  vnav is not allowed past the FAF, but i dont know if the approaches vertical guidance goes to the TT through the same labels .. 


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Post Options Post Options   Thanks (0) Thanks(0)   Quote R0bst3r Quote  Post ReplyReply Direct Link To This Post Posted: 06 Nov 2022 at 9:16pm
Avisteve,

Great to hear this issue is getting looked into. I opened case #IFD00090258 on this. My issue and configuration is identical to Pburger’s. 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote AviSteve Quote  Post ReplyReply Direct Link To This Post Posted: 06 Nov 2022 at 9:48pm
Originally posted by ricardo ricardo wrote:

pburger -- 

have you tried disabling the labels and testing whether you still get vertical guidance in an approach.

..  vnav is not allowed past the FAF, but i dont know if the approaches vertical guidance goes to the TT through the same labels .. 


Disabling VNAV Labels in Maintenance Mode would cause the IFD to stop sending the vertical deviation label used for approaches.
Steve Lindsley
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Merlinspop Quote  Post ReplyReply Direct Link To This Post Posted: 13 Nov 2022 at 2:17pm
A&P and I got errors trying to do the upgrade, but found this while trying to find info regarding our upgrade issue.  Our set up is IFD-Aerocruz-Dynon HDX.  
We’ll be reaching out to tech support and local dealers starting tomorrow.  This bug, though, makes me wonder if it would be better to revert to 10.2.x.
To help with that decision, I have a question:
Since our install includes a source selection switch for the AP, either the IFD540 can drive it (GPSS) or the HDX can drive (point to point). If the source selection is set to the HDX side, the connection between between the HDX and the AP is RS232.  I believe the altitude labels are not passed over the RS232, correct?  Not ideal, but at least on long IFR cruising legs, the switch could be flipped to HDX and the AeroCruz would continue to hold set altitude regardless of altitude constraints entered into the IFD, correct?  Seems to be a awfully clunky solution to use in IMC, though.


Edited by Merlinspop - 13 Nov 2022 at 2:57pm
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