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  #1  
Old 11-21-2019, 04:20 PM
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catmandu catmandu is offline
 
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Default TruTrack GPS data matching?

Put a PM out to Lucas, because he mentioned in another thread it matters for a G3X, but maybe someone else knows for this particular setup:

Installed Equipment:

TruTrak Vizion 385
GRT HXr as primary display, no integrated GPS
GRT Horizon WS secondary display, GPS module attached, feeds GPS to the HXr via Display link.

Now I'm installing a Garmin GNX375

The ARINC data to the Vizion will be switchable between the HXr and the 375. Does the Serial data path to the Vizion have to match / be switched simultaneously? If not, is there a particular reason for the Vizion to use one GPS serial source over the other?

Does the second serial port on the Vizion (shown as unused) come into play?

Schematics hurt my brain . . .
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  #2  
Old 11-21-2019, 05:07 PM
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Skid Skid is offline
 
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Location: Walworth, WI
Posts: 157
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I have an IFR GPS, was a GNS430 now an Avidyne IFD440, feeding my GRT EFIS via an ARINC and a switch so the A/P can be driven directly from the IFR GPS? I always leave the switch set to the EFIS.

Do you have the vertical A/P commands on your EFIS? I upgraded to Vizion 385 this year. I also added the vertical A/P commands. I now drive the A/P with the commands on the EFIS and do not touch the Vizion.

The only reason to switch the A/P to the IFR GPS is if the EFIS fails. Or am I not understanding your question?
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  #3  
Old 11-21-2019, 05:11 PM
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rleffler rleffler is offline
 
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Location: Delaware, OH (KDLZ)
Posts: 4,118
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Quote:
Originally Posted by catmandu View Post
Put a PM out to Lucas, because he mentioned in another thread it matters for a G3X, but maybe someone else knows for this particular setup:

Installed Equipment:

TruTrak Vizion 385
GRT HXr as primary display, no integrated GPS
GRT Horizon WS secondary display, GPS module attached, feeds GPS to the HXr via Display link.

Now I'm installing a Garmin GNX375

The ARINC data to the Vizion will be switchable between the HXr and the 375. Does the Serial data path to the Vizion have to match / be switched simultaneously? If not, is there a particular reason for the Vizion to use one GPS serial source over the other?

Does the second serial port on the Vizion (shown as unused) come into play?

Schematics hurt my brain . . .
The ARINC and the serial feed should be from the 375, especially if you want to fly IFR.

The auxiliary serial port on the Vizion isn’t used.

You don’t have to switch the serial line. You can wire both inputs in parallel. In my RV-10, I’ve got the gps serial going to multiple devices in addition to these.
There is no harm sending your gps coordinates in parallel to both devices.

I am not familiar with the HXR, so I can’t give specific comments. My original panel used AFS 4500s. I wired the ARINC lines to switch between the EFIS an d the Vizion. When I upgraded to AFS 5500s, I took the switch out and the GPS ARINC goes to the EFIS and the EFIS out to the Vizion. I know that some people feel that switch adds redundancy if the EFIS fails, but it also adds another single point of failure. You are going to want to control the Vizion from the HXR 99.99% of the time. When that 0.01% happens, you’ll want to use the gps on the WS and land ASAP. I personally would leave the arinc switch out. Less points of failure.
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  #4  
Old 11-21-2019, 05:24 PM
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Skid Skid is offline
 
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Location: Walworth, WI
Posts: 157
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Quote:
Originally Posted by catmandu View Post
Put a PM out to Lucas, because he mentioned in another thread it matters for a G3X, but maybe someone else knows for this particular setup:

Installed Equipment:

TruTrak Vizion 385
GRT HXr as primary display, no integrated GPS
GRT Horizon WS secondary display, GPS module attached, feeds GPS to the HXr via Display link.

Now I'm installing a Garmin GNX375

The ARINC data to the Vizion will be switchable between the HXr and the 375. Does the Serial data path to the Vizion have to match / be switched simultaneously? If not, is there a particular reason for the Vizion to use one GPS serial source over the other?

Does the second serial port on the Vizion (shown as unused) come into play?

Schematics hurt my brain . . .
Mike,
I can send you my schematic if that would help you.
Let me know.
Mark
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  #5  
Old 11-21-2019, 05:57 PM
BobTurner BobTurner is offline
 
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Location: Livermore, CA
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Default Clear as mud

In 2010, when I investigated this exact same question, TruTrak said ‘no’, the RS232 gps line did not need to be switched, just the ARINC lines. Trio, on the other hand, recommended switching both. Since I decided on a Trio (and would make the same choice again-it’s a great autopilot) I put in a 3 pole, double throw switch.
Other Bob: I strongly disagree with the ‘no switch’ approach. If the switch fails, you lose the full functionality of the autopilot. This should be an inconvenience, at worst. But should the primary efis fail, you might (depending on back ups, etc) really want the autopilot to work, including a gps approach capability.
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  #6  
Old 11-21-2019, 09:23 PM
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Plummit Plummit is offline
 
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Quote:
Originally Posted by catmandu View Post
Put a PM out to Lucas, because he mentioned in another thread it matters for a G3X, but maybe someone else knows for this particular setup:
FYI, Lucas is no longer with TT.

-Marc
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  #7  
Old 11-21-2019, 10:08 PM
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rleffler rleffler is offline
 
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Quote:
Originally Posted by BobTurner View Post
Other Bob: I strongly disagree with the ‘no switch’ approach. If the switch fails, you lose the full functionality of the autopilot. This should be an inconvenience, at worst. But should the primary efis fail, you might (depending on back ups, etc) really want the autopilot to work, including a gps approach capability.

Not entirely correct and options may be limited, but there are options.

I didn’t lose an efis, but I did lose my arinc adapter on an IFR flight. My GTN650 was still working fine and I could see if I was on the intended course without an issue. I still could use the autopilot as well, except nothing was talking to it. I had complete manual control. I had no problem with following the course display on the GTN 650 manually. I had no difficulties flying a standard step down gps approach. Of course you can always hand fly the approach too, with guidance from the certified navigator.

I will admit, it’s not something I would want to do to minimums, but it’s an option. Anything below MVFR and I would do a direct route to the nearest vfr alternative.

I also happen to have three AFS screens and a Trutrak Gemini in my panel. While losing the PFD would be inconvenient, it’s not the end of the world.

The OP also has a MFD with a non-certified GPS connected. While technically not legal for IFR operations, it can provide great situational awareness and provide position information on a moving map. I don’t know about the WS capabilities, but I can display an approach plate, sectional, or IFR chart on my AFS 5500 MFD and my position will be displayed on the plate.

As long as the certified gps is operational, the display is within the required viewing distance, and you see the NAV screen, you’re still legal.

This is no right or wrong, or my solution is better than your solution, conversation. It’s really about doing the due diligence required for proper panel design and then ensuring you practice all the various emergency procedures until you’re proficient.

Questions to ask:

1. Is vfr or IFR a requirement?
2. On paper, fail each device in your panel. What is your plan b to mitigate that device’s failure in the air? In a real situation this is where the Vizion’s hold track and altitude button buys you think time.
3. If there isn’t an obvious plan b, then what do you have to change in you panel design to give you one?
4. Run through other failure scenarios that make take out multiple devices. I.e. electrical issues
5. If you answered vfr to the first question, this is all academic but will help you understand your panel limitations better.
6. Document all your various plan b’s in you POH.

In a recent IPC, I had a very competent CFII and corporate pilot start failing devices on me. He gave up after about 15 minutes. My panel design took those failures into account, each one was documented in my POH, and I had practiced flying in each failure mode.

At some point, you do end up chasing your tail with too much redundancy. Too much redundancy can also cause complexities that complicate the situation. Everyone needs to determine where that fine line is in their own panel.
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  #8  
Old 11-22-2019, 06:37 AM
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catmandu catmandu is offline
 
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After some sleep, and with y'all's help, I think I will just run serial data from the 375 directly to the Vizion, HXr, and WS via an unswitched path. That data will be GPS1 on the GRT equipment (normally selected), and the module on the WS as GPS2. Locking MilSpec DPDT toggle switch for the ARINC data to the Vizion from (primarily) the HXr, or the 375.

The ability to have the Vizion fly a coupled approach with an HXr failure outweighs the risk of failure for that particular switch, for me anyway.

Thanks.
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  #9  
Old 11-22-2019, 02:23 PM
BobTurner BobTurner is offline
 
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Quote:
Originally Posted by catmandu View Post
The ability to have the Vizion fly a coupled approach with an HXr failure outweighs the risk of failure for that particular switch, for me anyway.

Thanks.
Same for me. But one suggestion. I haven’t actually used the autopilot in ‘direct to gps’ mode since phase 1. Every year at annual, I try to re-read the Trio manual. Otherwise I’m sure I would forget how to use it in stand-alone op.
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  #10  
Old 11-22-2019, 05:59 PM
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catmandu catmandu is offline
 
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Quote:
Originally Posted by BobTurner View Post
Same for me. But one suggestion. I haven’t actually used the autopilot in ‘direct to gps’ mode since phase 1. Every year at annual, I try to re-read the Trio manual. Otherwise I’m sure I would forget how to use it in stand-alone op.
Excellent advice. Annually prior to the condition inspection, I test my "30 minutes to get on deck in IFR" backup battery, just to make sure it goes past 29 minutes. And then I replace it anyway, because $25 is cheap insurance. If I had it to do over, I'd use the EarthX backup battery, and test but not replace it, which works out about the same cost wise over the life cycle.
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