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Garmin GTX35R ADS-b setup

von_flyer

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If I install and have calibrated the GAE12 encoder, do these connections look proper for ADS-b data being sent to the transponder. Without the GAE we are not seeing any altitude data on FlightAware, etc.
 

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If I install and have calibrated the GAE12 encoder, do these connections look proper for ADS-b data being sent to the transponder. Without the GAE we are not seeing any altitude data on FlightAware, etc.

John,

It should not be necessary to install a GAE 12 altitude encoder on your GTX 35R installed with a G3X Touch system.

The GTX 35R receives altitude data directly from the GSU 25 ADAHRS.

Rather than relying on Flightaware, you might want to request an ADS-B PAPR report for one of your flights.

Steve
 
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Thank you for the response Steve.

I did read that it would not pass the ADS-b report without using a GAE12 as the altitude source. But, with that being said I still should have altitude readout from the transponder with the current setup I thought, like you said.

Perhaps I have the wrong format for the serial comms between devices.?. See the attached serial connection. What is the proper data format for this?

I use FlightAware to do quick checks of seeing any altitude being reported when the owner flies the airplane. I have requested the FAA report and it of course failed for no altitude reported.
 

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Thank you for the response Steve.

I did read that it would not pass the ADS-b report without using a GAE12 as the altitude source. But, with that being said I still should have altitude readout from the transponder with the current setup I thought, like you said.

Perhaps I have the wrong format for the serial comms between devices.?. See the attached serial connection. What is the proper data format for this?

I use FlightAware to do quick checks of seeing any altitude being reported when the owner flies the airplane. I have requested the FAA report and it of course failed for no altitude reported.

John,

Not sure where you read that it would not pass an ADS-B report without using a GAE12, but that is incorrect.

As shown on the attached wiring and configuration page from the G3X Touch installation manual, there is no configuration required for either the GTX 35R serial port 1 or the GSU 25 serial port 3 in this installation.

All that is needed is to use the Transponder configuration page on the PFD and select GTX 35R as the transponder and verify that you get a green check mark for good communication between the GSU 25 and the GTX 35R.

Steve

View attachment GTX 35R Wiring_Configuration.pdf
 
XPDR Configuration

Thank you for the response Steve.

I did read that it would not pass the ADS-b report without using a GAE12 as the altitude source. But, with that being said I still should have altitude readout from the transponder with the current setup I thought, like you said.

Perhaps I have the wrong format for the serial comms between devices.?. See the attached serial connection. What is the proper data format for this?

I use FlightAware to do quick checks of seeing any altitude being reported when the owner flies the airplane. I have requested the FAA report and it of course failed for no altitude reported.

Steve is correct. Remote control of the transponder and pressure altitude data are included on the serial connection between the transponder (port 1) and the GSU 25 (port 3). These ports are hard coded, no configuration is required.

Are you able to remote control your transponder as the system is set up right now?

Thanks,

Justin
 
I do have the green check mark on the transponder configuration page. However on the system information page/device list the XPDR has a red X. On the transponder Info tab the pressure altitude has a red X and says Invalid. The RS-232 Input line has a green check mark by AHRS RS-232 3.
 
I do have the green check mark on the transponder configuration page. However on the system information page/device list the XPDR has a red X. On the transponder Info tab the pressure altitude has a red X and says Invalid. The RS-232 Input line has a green check mark by AHRS RS-232 3.

John,

A couple of questions:
1. Is the GTX 35R using the latest V2.63 software?
2. Does the GTX info tab still indicate invalid pressure altitude when the GAE 12 is removed?
3. Has anyone attempted to configure the GTX 35R with a laptop over USB? All GTX configuration should only be done via the PFD Transponder page. You might try re-editing something on the PFD Transponder configuration page to make sure it overwrites any old configuration in the GTX 35R if a PC configuration tool was used at some point.

Steve
 
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I will be out to the hangar in the next couple days. I’ll check the items you mentioned.
Thank you for the input.
 
John,

I removed the transmit wire from the GSU 25 to the GTX 35R, and left the transmit wire from the GTX 35R to the GSU 25 as a test.

This caused the GTX 35R to be shown with a red-x (failed communications) on the System Information page, so I think this rules out the possibility that the GTX 35R is not receiving transmissions from the GTX 35R since you are not seeing a total communication failure. It would seem that the bi-directional wiring between the GSU 25 and the GTX 35R is intact.

What G3X Touch software are you using?

Steve
 
For an additional consideration, I personally would not want to the GAE if you have a G3X or a G5. If you have the GAE, you are not seeing the altitude that your transponder is using on your primary flight display. If it is sensing the wrong altitude, you might not know it for a while. In addition, when you take it to have an IFR cert (91.411, 91.413) inspection done, they will have to check both and probably charge you more money.
The GAE is great for an aircraft that doesn't have a G5 or G3X, but if you have either of those, sell the GAE and keep it simple!
-Levi
 
In addition, when you take it to have an IFR cert (91.411, 91.413) inspection done, they will have to check both and probably charge you more money.
The GAE is great for an aircraft that doesn't have a G5 or G3X, but if you have either of those, sell the GAE and keep it simple!
-Levi

Yep what he said, GAE with G3X just makes things harder and is another source of error.
 
Good to know about the GAE12, I have one in my own RV-7 with a GTX335 but GRT screens.

I spent more time on the 35R/25 issue and learned more details. The green check marks are there except for “pressure altitude” is “invalid”. The owner mentioned that the altitude calibration has not been done by the avionics shop yet.

Does this add up that if the PA is invalid the output would be 0’ ?

So now we are setting up the avionics shop to do their thing.
 

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The owner mentioned that the altitude calibration has not been done by the avionics shop yet.
John,

There is no requirement to calibrate the GSU 25 unless it does not pass an air data test.

Does the PFD report the correct field altitude?

There is no indication in your screen shots that there is anything wrong with GSU 25 except the OAT reading should not be 185 degs F.

I would fix the OAT probe and update the G3X Touch and GTX 35R software before doing anything else.

Steve
 
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...maybe he was on the ramp somewhere in south Texas? :)

The plane was last seen flying in Michigan, so probably not. :)

BTW, the GPS 20A is also not properly installed and/or configured to provide compliant GPS position data to the GTX 35R, so this plane has many problems.

Steve
 
BTW, the GPS 20A is also not properly installed and/or configured to provide compliant GPS position data to the GTX 35R, so this plane has many problems.

Steve

Can you explain this? Is it something you see on the screen shots?

I appreciate your input.
 
Can you explain this? Is it something you see on the screen shots?

I appreciate your input.

John,

The recent flights (e.g. 2 hrs on June 15) are showing non-compliant GPS data which will show up as NIC, SIL, and SDA failures in the Integrity and Accuracy section of the PAPR report.

I would start by checking the GTX 35R configuration and make sure that it is told that the GPS 20A is connected to RS-232 port 2 of the GTX 35R as shown on page 27-34 of the Rev. AP G3X Touch installation manual.

GPS20A GTX Config.png

Update: I notice that the GPS 20A data is being received and used by the GTX 35R on the previous day (June 14), so something changed before the June 15 flight.

Steve
 
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