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04-10-2017, 07:25 PM
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Join Date: Dec 2011
Location: Livermore, CA
Posts: 6,797
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I'd suggest putting in a "stand alone" switch. If things go really wrong (e.g., dark or IMC and EFIS dies) it might be nice to just be able to fly straight and level.
But to your issue: Do I understand that everything (EFIS, autopilot) worked okay before you installed the ARINC wires? Since you found one wiring error, did you triple check the others? You should have ARINC A OUT from the EFIS to ARINC A IN on the Trutrak, and ARINC B OUT from EFIS to ARINC B IN on the Trutrak.
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04-11-2017, 07:20 AM
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Join Date: Sep 2007
Location: Hudson County, NJ
Posts: 1,092
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Quote:
Originally Posted by BobTurner
I'd suggest putting in a "stand alone" switch. If things go really wrong (e.g., dark or IMC and EFIS dies) it might be nice to just be able to fly straight and level.
But to your issue: Do I understand that everything (EFIS, autopilot) worked okay before you installed the ARINC wires? Since you found one wiring error, did you triple check the others? You should have ARINC A OUT from the EFIS to ARINC A IN on the Trutrak, and ARINC B OUT from EFIS to ARINC B IN on the Trutrak.
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I may have a stand alone switch. I have some type of toggle between my two GPS sources (GRT and G3X (moving map only)). As I understand it, the switch allows me to direct one source over the other to the A/P for things like flying a flight plan. I can't say how it is intended to work though given the fact that the G3X is external to the EFIS. I know you can define a GPS2 in the EFIS, but I have never played around with that because the wing leveler that was originally in the plane never worked. But my point is, someone put some thought into this set-up when it was built. I think Stein was involved in the original panel to a certain degree. I remember seeing some instructions from him about how to set-up the equipment that he sold the builder.
Quote:
Originally Posted by BobTurner
But to your issue: Do I understand that everything (EFIS, autopilot) worked okay before you installed the ARINC wires?
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Sort of. When I had the A/P installed where the old wing leveler was, Saint Aviation prewired the ARINC connections into the harness. Then, the plugs were tied off out of the way. SO, the A/P worked perfectly with the EFIS while the ARINC module was not installed, and the plugs for it sat idle off to the side.
After deciding that it was worth having the ARINC installed, I bought one and plugged it in. I turned the ARINC Installed? option in the General Setup menu of the EFIS to "Y." At that point, the "problems" began. I immediately began getting the ARINC data warnings, AND the A/P would not behave in what to me seemed like a rational way.
I'm pretty sure the plugs added to the harness for the ARINC installation are correct with the exception of the one I made correct after the fact.
I think I need to absorb some of this for a while. One thing that still bothers me is GRT is really clinging to a need to point the EFIS to the ARINC module on serial port 4. The believe the EFIS software version was old and the option to direct the EFIS to a particular port to look for the ARINC was missing in the old software. But this is not the case though as I have the current software. But they keep bringing this up so it seems significant.
I think I have an easier way to test the A/P. That is to unplug the ARINC and turn off the option in the EFIS. In theory, I should be back to a working A/P like I had before I attempted to add the ARINC.
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04-11-2017, 09:54 AM
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Join Date: Jun 2008
Location: Kalamazoo, MI
Posts: 263
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Andy,
You originally stated you have an early GRT Sport. It likely has a built in GRT GPS, usually connected to Serial port 3.
Like Bob, I also didn't understand your set up. There is no GNS 430 or GTN 650 or similar GPS navigator, correct? Your G3X is not one either.
You will have to follow your wiring. I would check with Stein if they originally made the panel or Jesse's crew may have made a wiring diagram. The switch may indeed allow you to select either the GRT GPS or G3X GPS to send RS232 GPS information to your autopilot. This will provide horizontal steering only, no vertical steering and no GPSS steering.
I have older Sports also and ARINC, but no autopilot. My ARINC is connected to serial port 4 of my primary Sport. However, in General Setup page, serial port 4 in and out are set to OFF since I am not using the serial port 4 provided on the ARINC module. I think GRT tech support may be mistaken here. The ARINC module connects to the Sport over the Sport serial port 4. Since that makes that port unavailable for other uses, GRT added a serial port to the ARINC module to replace the one the module took away from the EFIS. If you use the "extension port", you have to tell (define) it's use to the EFIS just like any other port. But you aren't using it, so your Serial Port 4 in and out should be OFF. This has been standard in the software for years.
Bob is the autopilot expert, certainly not me! But, does your autopilot work correctly by itself? Meaning just using it's front panel controls? Then if you connect just the RS232 signal, does the EFIS control it properly? This should be how you have been using it until now. Can you use the switch and control the autopilot with the G3X?
GRT Sport EFIS require an upgrade to support vertical autopilot commands. Do you have this?
You might want to put your thoughts together and the results of your investigation and post it on the GRT Community Forums. GRT's Jeff, who does all the software programming monitors that forum and provides answers. He is probably the most qualified person to assist.
Keep us posted!
Jim Butcher
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04-11-2017, 11:50 AM
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Join Date: Sep 2007
Location: Hudson County, NJ
Posts: 1,092
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Hi Jim. Here are some responses. Thanks!
Quote:
Originally Posted by h&jeuropa
Andy,
You originally stated you have an early GRT Sport. It likely has a built in GRT GPS, usually connected to Serial port 3. Yes, and it is
Like Bob, I also didn't understand your set up. There is no GNS 430 or GTN 650 or similar GPS navigator, correct? Your G3X is not one either. I'm not sure about this. It is a moving map GPS with flight planning capabilities. It just does not have AHARS or ADAHRS. So it can't be used as a PFD but it is as much of a moving map as the internal GPS on the GRT EFIS
You will have to follow your wiring. I would check with Stein if they originally made the panel or Jesse's crew may have made a wiring diagram. The switch may indeed allow you to select either the GRT GPS or G3X GPS to send RS232 GPS information to your autopilot. This will provide horizontal steering only, no vertical steering and no GPSS steering. I could look for the Stein information but there wasn't any harness info. It was just a page of instructions for connecting the equipment the builder purchased. I don't think it even went as far as the individual pin and plug level of detail.
I'll take you word for on the steering because I can't refute it. BUT using the A/P control head before I injected the ARINC into the equation, the A/P would fly GPS NAV of my flight plan in the GRT EFIS, and I was also able to specify through the A/P a preset altitude to climb or descend to, and at what rate of climb or descent. I guess that was the A/P capability aside from the information the EFIS was sending to the A/P. And yes, I believe the toggle switch was simply allowing me to independently decide which flight plan I wanted to send to the A/P. That is, the GRT plan, or the G3X plan.
I have older Sports also and ARINC, but no autopilot. My ARINC is connected to serial port 4 of my primary Sport. However, in General Setup page, serial port 4 in and out are set to OFF since I am not using the serial port 4 provided on the ARINC module. I think GRT tech support may be mistaken here. The ARINC module connects to the Sport over the Sport serial port 4. Since that makes that port unavailable for other uses, GRT added a serial port to the ARINC module to replace the one the module took away from the EFIS. If you use the "extension port", you have to tell (define) it's use to the EFIS just like any other port. But you aren't using it, so your Serial Port 4 in and out should be OFF. This has been standard in the software for years. This is my understanding and exact setup as well.
Bob is the autopilot expert, certainly not me! But, does your autopilot work correctly by itself? Meaning just using it's front panel controls? Then if you connect just the RS232 signal, does the EFIS control it properly? This should be how you have been using it until now. When I got the A/P installed, I flew it using the A/P controls themselves. It would let me hold a course, climb and descend, and use control wheel steering (That is, turn deviate from the selected course by turning the knob on the A/P. I could also move past that initial control level (which you get when you turn the A/P ON) and turn on the GPS NAV mode which would fly the flight plan in the EFIS. I never tried to actually control the A/P directly from the EFIS menus. Can you use the switch and control the autopilot with the G3X? I believe I tested this successfully but I've tried to keep the G3X out of the discussion because I figured that just complicating things. If the EFIS and GPS and ARINC all work, I can worry about the G3X working later.
GRT Sport EFIS require an upgrade to support vertical autopilot commands. Do you have this? I don't believe I do. I never did the upgrade. So, like the G3X, I figure I can worry about that later (unless it might be part of the current problem!!)
You might want to put your thoughts together and the results of your investigation and post it on the GRT Community Forums. GRT's Jeff, who does all the software programming monitors that forum and provides answers. He is probably the most qualified person to assist. I may try this but it seems like I just have some type of novice issue that is a simple oversight. Maybe it is more sinister than that, but I just seems like it should be a simpler problem.
Keep us posted!
Jim Butcher
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04-11-2017, 12:55 PM
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Join Date: Sep 2007
Location: Hudson County, NJ
Posts: 1,092
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OK Jim, some of this is sinking in now. I guess by navigator, you me a radio or similar than can fly an approach using the autopilot. No, I do not have anything like that in my plane.
I think I need to go back and start at the A/P end of the chain now to confirm that the A/P is actually working. I presume now that it uses its own gyro and pitot/static input to control the pitch and roll servos. It just can't fly a course line, only a heading. And all vertical commands are simply based on current altitude and rate of change. I'm not sure why it took so long for me to separate the EFIS and the A/P in my head. I'll be back with some info in a few days I hope.
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04-11-2017, 03:30 PM
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Join Date: Jun 2008
Location: Kalamazoo, MI
Posts: 263
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Andy,
Yes. A navigator like GNS430 not only has a GPS but it has in it's memory all the approaches. So when you select an approach, it "knows" all the points (fixes) and altitudes. It is having all these brains that make them so expensive!
Which TruTrack do you have, Gemini AP?
Did Jesse do the AP install? If so, he probably knows how things are wired, especially "the switch".
I think your explanation of how your autopilot works is correct. The only thing to add is that it probably can follow a flight plan. It just will not have turn anticipation - it will fly to a point in the flight plan and then turn to the next point. Turn anticipation smooths those turns by starting them before you actually get to the point.
Why did you decide to add the ARINC capability? Were you looking for vertical autopilot modes?
I don't know how to tell if your Sport has the vertical autopilot software. Ask GRT Tech support.
I think you're making progress. Welecome to experimental aviation
Jim
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04-18-2017, 05:02 PM
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Join Date: Sep 2007
Location: Hudson County, NJ
Posts: 1,092
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OK guys, I'm back.
I think everything works now. I appreciate all the patience and help from you guys!!
I went to the hangar today to step back, and test each piece of equipment in the chain, beginning with the A/P itself. I removed the three wires from the A/P that were associated with the EFIS (RS232 for the internal GRT GPS, and the 2 ARINC wires). Then I flew the plane and tested the A/P alone. It worked. Then I added back the internal EFIS GPS and flight tested that. It worked. Then I added back the 2 ARINC wires and flight tested that. Fortunately, things worked this time. And to cut to the chase, what I think the problem was, aside from the 1 misplaced wire from before, was a baud rate setting mismatch between the GPS on serial port 3, and the A/P. Hard to believe...
To make a long story short, I feel like I learned a ton about the system and how it functions. FAR more than I cared to in the beginning. But looking back now, it seems like I would have been spoiled if it all worked when I plugged the ARINC in the first time. This was some sort of right of passage I guess.
Now I have to go and learn how to use the new equipment.
Thanks again for all the help!! Andy
PS. I did my 1st Pilots n Paws trip Saturday. Flew from NJ to NC and back to bring Krypton to a doctor to get him help with a really bad spinal issue. He was a happy dog! I could have used the A/P!!

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06-07-2020, 01:46 AM
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Join Date: Feb 2015
Location: Fort Worth
Posts: 26
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GRT Sport SX Serial Port 4 Setting for ARINC Module
I'm running into similar problems with my GRT Sport SX not controlling the auto pilot.
The system was working fine, but when I sent the Sport back to GRT to fix the screen the unit came back and this feature no longer works.
Configuration:
- Single GRT Sport SX
- GRT ARINC 429 External Module
- Garmin GNS-420W
- Trutrak Vision 385
Question:
In the GRT EFIS Settings and Values, what do I set the the "Serial Port 4 Input" and "Serial Port 4 Output" to?
Note:
I have "ARINC Module Connected | Yes"
Thank you in advance.
__________________
Blake Graham N801RH
Last edited by VIN2020 : 06-07-2020 at 01:49 AM.
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06-07-2020, 07:19 AM
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Join Date: Oct 2013
Location: Schaumburg, IL
Posts: 5,297
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Quote:
Originally Posted by VIN2020
I'm running into similar problems with my GRT Sport SX not controlling the auto pilot.
The system was working fine, but when I sent the Sport back to GRT to fix the screen the unit came back and this feature no longer works.
Configuration:
- Single GRT Sport SX
- GRT ARINC 429 External Module
- Garmin GNS-420W
- Trutrak Vision 385
Question:
In the GRT EFIS Settings and Values, what do I set the the "Serial Port 4 Input" and "Serial Port 4 Output" to?
Note:
I have "ARINC Module Connected | Yes"
Thank you in advance.
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I believe that GRT sells that as an option on the sport series. It is turned on or off via s/w config at that factory. I am guessing that they may have forgot to turn it back on after a s/w reload or factory reset.
Larry
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N64LR - RV-6A / IO-320, Flying as of 8/2015
N11LR - RV-10, Flying as of 12/2019
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