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

[SimPilotNL 3]

Second test flight, same result. The plane does not pick up the G/S.

Approach selected and activated in the GTN750. Speed 90 knots, flaps down 1 notch, gear down, APP mode active, ALT HOLD at published altitude, LPV indicated on the GTN750 screen.

I see the G/S indicators moving down on the HSI, but the plane does not react to them and just remains in ALT HOLD mode.

This is a new and fresh install of X-Plane, all aircraft and the GTN units. Downloaded all the latest installers. The only plugin that is active is X-Camera, I assume I am not the only one using X-Camera and the GTN unit.

[RXP 2,338]

I'm not familiar with this aircraft, but have you armed a vertical mode while still below the G/S? Otherwise I'd think the A/P wouldn't know you'd like to capture the vertical slope?

[SimPilotNL 3]

The airplane is the Carenado F33A BONANZA  which according to the Carenado website has "Support for RealityXP's GTN750* (integrated into 3D cockpit, when available)."

I intercept the G/S from below indeed in ALT HOLD mode with APP mode active. The autopliot should then pick up the glideslope and announce GS mode when it does. I have just tested this in the same airplane with the RealityXP  GTN750 switched off (which means using the default X-Plane GNS unit) and that works perfectly just as described above.
WIth the GTN750 enabled however the G/S is not picked up, the airplane just stays in ALT HOLD mode

I have also noticed that even while the RXP GTN750 unit is tied to the Master Avionics bus, it will not switch off when i switch off the Master Avionics after landing/parking.

[RXP 2,338]

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?

 

[SimPilotNL 3]

The only thing i could think of is the one addon that is stil running, which is X-Camera. For a test flight I can try to switch it off.
Also the GTN was not integrated by default in de Carenado Bonanza, I had to download an .ini file from to forums here to make that work. I assume the ini file is just to make it visible and cannot mess with the way the GTN actually works.

I have not tested this in my current setup after re-install because I really want to keep it as minimalistic as possible for the tests, but before re-install this same problem occured in any aircraft that I used the GTN unit in. Meaning this Carenado Bonanza F33A, but also the Baron B58 from Carenado.
Now thinking of that, I do/did have the Simcoders Reality Expansion Pack installed for both these aircraft. Could that be a problem? (Although I am pretty sure I'm not the only one using this combination, the REP brings so much extra to the Carenado aircraft).

Ill be doing another test flight this week and will let you know about the datarefs you asked me about. How do I check the values for these?

As always thanks for the answer/help Jean-Luc.

Edited July 30, 2018 by HansMatthijssen

[RXP 2,338]

I'm looking forward your feedback but I wouldn't be surprised REP is 'playing' with the A/P as well.

Besides, when I mention the Baron I mean the default Baron 58 included in the simulator, not any third party aircraft, just to cross check the issue is inherent to the GTN or the a combination of third party plugins.

As for checking the datarefs:
Plugins | Data Ref Editor | Show Data Refs

It should be installed standard with XP11 AFAIK, otherwise
https://developer.x-plane.com/tools/datarefeditor/

[SimPilotNL 3]

 

I found that dataref editor. Values seem to be what they should be.

Edited July 30, 2018 by HansMatthijssen

[RXP 2,338]

What about deactivating 'connect GPS to VOR indicator' ?

Also just in case it affects the operation, what about enabling 'Use Audio Panel' ?

[SimPilotNL 3]

I cannot enable the Audio Panel. I think that is because in the VC the GTN is placed over the top of the default Audio Panel and the GNS430 default unit.

I dont have time for test flight now, but will check later with the "connect GPS to VOR indicator" unchacked.

Would be nice to see the GTN settings of someone that does not experience any problems.

[RXP 2,338]

Even though you won't have access to the audio panel because it is masked/hidden, I'd suggest you enable the option to cross check if this has an effect internally in the trainer regarding the issue you are reporting.

[SimPilotNL 3]

On 7/30/2018 at 4:44 PM, RXP said:

What about deactivating 'connect GPS to VOR indicator' ?

This seems to have done the trick. In a testflight right now and the aircraft ( Carenado Bonanza F33A) did pick up the glideslope perfectly!

Great help as ever, much appreciated!

[RXP 2,338]

Thank you for your enduring patience!

Now the conclusion is interesting:

- when enabled, the GTN/GNS V2 override the NAV needles (using the X-Plane native dataref: "sim/operation/override/override_nav1_needles" - and "_nav2_" if GTN settings nav source is NAV2 ).

- it also override the "...nav#_hdef_dot", "...nav#_vdef_dot" and "...nav#_fromto"

- it does so in addition to the other independently controlled overrides (GPS, HSI).

Which makes me wonder if the issue is X-Plane failing to 'report' the needles/signal to other plugins when it is overriden (X-Plane bug) or if the issue is the 3rd party aircraft not picking up/handling the datarefs values, or lastly, if the GTN/GNS V2 is missing a few other datarefs to also override to make third party happy.

The later won't account why the third party aircraft is picking up things correctly when disabling 'override VOR' though. This leads me to suspect something in X-Plane or third party only?!?!

[SimPilotNL 3]

And then the next test flight it didn not pick up the GS again.

I must be doing something wroing, forgetting something (if you do a "Load and Activate Approach" could it be that you need to Activate it once more from the Flight Plan page maybe?).
Anyway it worked the previous flight to the unit is fine (although it does still not swith off with the Master Avionics switch after landing, but thats no big deal). So I am going to repeat these flights and see what does/does not make it work.

No problem at all Jean-Luc, the Reality XP units are great addons, so if I can help figure out why this is happening it might help to make the product even better. I'll keep posting my findings.

Edited July 31, 2018 by HansMatthijssen

[SimPilotNL 3]

Second and third test were also negative, the GTN750 did not pick up the glideslope.

After that I could only conclude that is most probably has something to do with the Simocders Reality Expansion Pack that I am using for the Carenado planes. So, I decided to load up the default Cessna 172SP and activate the GTN750 unit. I flew out, loaded and activated my approach (I keep flying the RNAV GPS RWY24 into Monauk, KTMP) and the GTN750 had no problems picking up the glideslope this time.

Preliminary conclusion seems to be that the GTN unit does not work correctly with the Simcoders REP. To test that further I am going to disable/uninstall the REP pack for the Carenado Bonanza F33A (my original aircraft that had problems) and try again.

I'll keep you posted.

[SimPilotNL 3]

I edited my last post, but apparently that didn't come through.

So, I disabled the Simcoders Reality Expansion Pack (REP) for the Carenado Bonanza F33A and tried my same testflight again. Contrary to what I expected, the aircraft did not pick up the glideslope and remained in ALT HOLD mode. And again after landing when i turned off the master avionics switch, the GTN750 unit was not powered down.

So a summary:

• Carenado Bonanza F33A with REP: GTN750 does not pick up the glideslope. GTN750 remains powered on after switching off master avionics
• Carenado Bonanza F33A REP disabled: GTN750 does not pick up the glideslope. GTN750 remains powered on after switching off master avionics
• Default Cessna 172SP: GTN750 picks up the glideslope without any problems.
• All three aircafft: Using the X-Plane default GNS430 unit they all pick up the glideslope perfectly.

I have no idea what's going on, but it is getting a little bit frustrating by now.
I really do not want to be limited to default X-Plane aircraft using the GTN750. I bought it (same reason I bought the Carenados with the REPs) for added realism.