GTN750 not picking up GS on RNAV/LPV approach (resolved)

[fppilot 4,371]

I would suggest that a handful of posts and responses, particularly here on the 4th page, be assembled into a pinned topic, and appropriately in both the Xplane and FSX/P3D forums as the material is not specific to one.

[tylenolwithwings 1]

I heard from Carenado on the particular issue with the GTN and the 177 Cardinal. You can open the manifest.json file in the 177 airplane folder and edit the "gps_power" value from 0 to 1. Then all you have to do is turn off the GTN and turn it back on for the NAV and GS to work properly. 

[theohall65 64]

On 7/28/2018 at 9:00 PM, RXP said:

I'd guess we would need other customers reporting a similar issue, or not, to find out what this could be. I'd guess should this be a GTN issue only, there would have been more reports and with more different aircraft.

This kind of problem might be related to something else in the Carenado aircraft 'enforcing' the A/P to work a certain way, effectively disabling our 'override'.

Nevertheless, the issue could be more recently due to the latest X-Plane updates?!? The way our A/P system work is very simple: if there is a lateral mode armed or engaged, it drives the F/D lateral. if there is a vertical mode engaged (in fact GLIDE_ON - i.e. 2048 in the X-Plane autopilot state datarefs), it also drives the F/D vertical. Furthermore, if a lateral mode is armed only, and there is a LCDI signal below 95% deflection, it automatically engages autopilot lateral mode.

Which leads me to think something in X-Plane, or with this aircraft, is no longer making the A/P see our GTN LCDI/VCDI signal as valid, therefore, it is not engaging the vertical mode but leave it armed only.

Are you sure the X-Plane HSI is connected to GPS and not to NAV1 or NAV2?

You can cross check the "sim/cockpit2/radios/actuators/HSI_source_select_pilot" for this (0: nav1, 1: nav2, 2: GPS).

Also can you please cross check "sim/operation/override/override_gps" and see if it is 1?

 

Here is another customer reporting exactly the same issue, only using the Citation II.

Remove the GTN 750, APPR mode works perfectly.

Install the GTN 750, the APPR light stays yellow and the plane never intercepts the glideslope.

Running 11.31 of X-Plane 11.  Just bought and installed the GTN 750 today.

[Brent 2]

18 hours ago, theohall65 said:

You can cross check the "sim/cockpit2/radios/actuators/HSI_source_select_pilot" for this (0: nav1, 1: nav2, 2: GPS).

Also can you please cross check "sim/operation/override/override_gps" and see if it is 1?

I'm experiencing the same issue with the Carenado B58 (ILS works fine).  Excuse my ignorance but where do I check these entries (full path please) that you mentioned?

[ibgregr 4]

22 hours ago, theohall65 said:

Here is another customer reporting exactly the same issue, only using the Citation II.

Remove the GTN 750, APPR mode works perfectly.

Install the GTN 750, the APPR light stays yellow and the plane never intercepts the glideslope.

Running 11.31 of X-Plane 11.  Just bought and installed the GTN 750 today.

Same here...Carenado Citation II.  Never captures GS...NAV and APPR stayed in ARMED state.

Switched over the the default Baron B58 and flew the exact same flightplan and it work beautifully.

So Carenado is doing something weird that is causing this to not work correctly.

 

X-Plane 11.31   and latest version of GTN 750  

Edited February 2, 2019 by ibgregr

[sjed 9]

I have the Carenado Citation with GTN750 and I'm experiencing the same problem everyone else is. Namely not capturing the descent on an LPV  approach. I have the latest 11.31 xplane v1.2 citation and 2.5.11 GTN750.  In an attempt to get some more in depth information, I checked the Garmin manuals, specifically the Garmin 725/750 pilots guide pdf.  Section 4.3.3.6 explains "Transition to Approach". It says IF transition to approach is enabled, you will approach from below the glidescope and vertical guidance will take over. IF, on the other hand, the transition to approach is NOT enabled, VNAV will terminate at the fix before FAF. Doesn't this sound like the problem we are all having. It goes on the explain that "function availability is dependent on installer configuration" and for further information to refer to the AFMS. Does anyone know what that is. Is it possible that our installed configurations don't have this "transition to approach" enabled correctly? 

[ibgregr 4]

5 minutes ago, sjed said:

I have the Carenado Citation with GTN750 and I'm experiencing the same problem everyone else is. Namely not capturing the descent on an LPV  approach. I have the latest 11.31 xplane v1.2 citation and 2.5.11 GTN750.  In an attempt to get some more in depth information, I checked the Garmin manuals, specifically the Garmin 725/750 pilots guide pdf.  Section 4.3.3.6 explains "Transition to Approach". It says IF transition to approach is enabled, you will approach from below the glidescope and vertical guidance will take over. IF, on the other hand, the transition to approach is NOT enabled, VNAV will terminate at the fix before FAF. Doesn't this sound like the problem we are all having. It goes on the explain that "function availability is dependent on installer configuration" and for further information to refer to the AFMS. Does anyone know what that is. Is it possible that our installed configurations don't have this "transition to approach" enabled correctly? 

I'm not sure about that setting.  But just for another test I loaded up the Carenado Piper PA-31 Navajo and it flew the approach  just like it should.  So it's not all Carenado planes but seems to be something with the Citation II.

Edited February 2, 2019 by ibgregr

[theohall65 64]

Well, I re-installed the GTN 750 leaving it at default settings other than specifying where X-Plane was installed.  Still had the problem.  But - as other have pointed out....

Once you start X-Plane and load your flight, disable the GTN 750 (just uncheck it in the plugins menu), then re-start your flight and enable the GTN 750.  Disabling and re-enabling the GTN 750 without re-starting the flight won't fix the issue.  I have to do this every time I start X-Plane, but only when I start X-Plane.  Works just fine after that.

This isn't a Carenado thing, it is a RealityXP GTN 750 thing.  Without the GTN 750, the Carenado planes never had an issue, for me, related to NAV and APPR in AP.

Edited February 3, 2019 by theohall65

[ibgregr 4]

7 hours ago, theohall65 said:

Well, I re-installed the GTN 750 leaving it at default settings other than specifying where X-Plane was installed.  Still had the problem.  But - as other have pointed out....

Once you start X-Plane and load your flight, disable the GTN 750 (just uncheck it in the plugins menu), then re-start your flight and enable the GTN 750.  Disabling and re-enabling the GTN 750 without re-starting the flight won't fix the issue.  I have to do this every time I start X-Plane, but only when I start X-Plane.  Works just fine after that.

This isn't a Carenado thing, it is a RealityXP GTN 750 thing.  Without the GTN 750, the Carenado planes never had an issue, for me, related to NAV and APPR in AP.

Well..I think I've tried what you just said..but it's not working.  Can you give me the exact steps you went through..(ie click on this, then this, etc) so that I know I'm doing exactly what you did?  Especially when it comes to "restarting the flight". Thanks for your help!

[theohall65 64]

Okay...

1) Start X-Plane

2) Load your flight.

3) Check to see if the GTN 750 is already enabled in the plugins menu.  If not enable, it.

4) Load a flight plan or just specify waypoints in the GTN 750, turn on the autopilot, select GPS and press NAV.  If you get the Green "On" light, no need to do anything else.  If not... on to step 5.

5) Disable the GTN 750 in the plugins menu.

6) Go to Flight Configuration, click on Change Location (even though you aren't changing location), and click Start New Flight.

7) Enable the GTN 750 in the plugins menu and repeat step 4.  I had a hiccup today where I had to do steps 5 and 6 twice before it worked - no idea why.

Edited February 4, 2019 by theohall65

[ibgregr 4]

12 hours ago, theohall65 said:

Okay...

1) Start X-Plane

2) Load your flight.

3) Check to see if the GTN 750 is already enabled in the plugins menu.  If not enable, it.

4) Load a flight plan or just specify waypoints in the GTN 750, turn on the autopilot, select GPS and press NAV.  If you get the Green "On" light, no need to do anything else.  If not... on to step 5.

5) Disable the GTN 750 in the plugins menu.

6) Go to Flight Configuration, click on Change Location (even though you aren't changing location), and click Start New Flight.

7) Enable the GTN 750 in the plugins menu and repeat step 4.  I had a hiccup today where I had to do steps 5 and 6 twice before it worked - no idea why.

Thanks for that.  I got it to work.  I originally missed that you said to totally disable the plugin...and I was just unchecking it from the Reality XP menu.  Just successfully made a flight and everything worked.

 

Now..at this point I do not know if I agree that this is a Reality XP issue or a Carenado.  On one had..the GTN 750 works flawlessly in every other plane I have tried.  So we know it works.  And it even works in a different Carenado plane (Navajo) without any issue.  So that's why I tend to lean towards Carenado.  Yes..toggling the GTN fixes it but that could just be due to something the Citation is doing/not doing during a normal startup.  I guess for now the work around will have to work.  I dont see the guy from Reality XP chiming in on this any longer so not sure he is even reading any of this.  I have opened a ticket with Carenado just to have that side covered since that state this plane works with the GTN 750.

Again..thanks for your step by step help!

 

[ibgregr 4]

4 hours ago, ibgregr said:

Thanks for that.  I got it to work.  I originally missed that you said to totally disable the plugin...and I was just unchecking it from the Reality XP menu.  Just successfully made a flight and everything worked.

 

Now..at this point I do not know if I agree that this is a Reality XP issue or a Carenado.  On one had..the GTN 750 works flawlessly in every other plane I have tried.  So we know it works.  And it even works in a different Carenado plane (Navajo) without any issue.  So that's why I tend to lean towards Carenado.  Yes..toggling the GTN fixes it but that could just be due to something the Citation is doing/not doing during a normal startup.  I guess for now the work around will have to work.  I dont see the guy from Reality XP chiming in on this any longer so not sure he is even reading any of this.  I have opened a ticket with Carenado just to have that side covered since that state this plane works with the GTN 750.

Again..thanks for your step by step help!

 

Quick update.  The above steps seem to be hit and miss for me.  It worked for that test I did...but I've tried it a couple times more this afternoon without any luck.  Oh well.  Sounds like Reality XP took out a line of code in the last update that is likely causing this issue and I read that they will add it back in for the next release which they said is coming soon.

[Adrian123 1,015]

Tried the approaches using both a the Default C90 and the Carenado P12. Neither pick up the glideslope. Just for curiosity, tried the PC12 in Prepar3d and worked perfect. Seems like perhaps an an issue with XP and the RXP and not a specific aircraft.

[RXP 2,338]

Hi,

yes we do read the forum and follow the discussion. This is valuable feedback and I thank you all.

The issue is multiple (it seems so far):

- There is an Aircraft vs GTN init problem: which plugin gets first initialized whether the aircraft plugin or the RXP plugin. This is why when you disable/enable the GTN it picks up with the aircraft, because probably the aircraft is expecting a certain 'order' and won't work with the GTN is the GTN initializes first (or last depending).

- There is GTN init problem: thanks to other discussion about the 'Reload Plugin' not working, we've identified an issue with the way the GTN (and GNS V2) plugin initialize depending if you load directly in an aircraft, change aircraft when already loaded etc... Thus the "Change Location (even though you aren't changing location)" working too because it forces a re-init of some datarefs.

- There is a GTN v2.5.11 problem: we're removed some code which used to 'ARM' the NAV mode under some conditions. We suspected this was old XP9 code no longer necessary because this is supposed to be handled by the aircraft, not the GTN. But it is not black and white, see here:

https://forums.x-plane.org/index.php?/forums/topic/164668-cessna-citation-550-autopilot-support/&page=2&tab=comments#comment-1581255

The upcoming v2.5.12 update should correct all this.

[ibgregr 4]

2 hours ago, RXP said:

The upcoming v2.5.12 update should correct all this.

Do you have any ETA on the new release?