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

[SimPilotNL 3]

Since a week none of my planes pick up the glideslope on any RNAV/LPV approach using the GTN750.

It is probably either a fake-pilot error, or something is wrong in my setttings, but I cannot pinpoint the problem, so I'm asking my fellow simpilots for help.
I load and activate a LPV approach in the GTN750 (various fields and planes attempted, Carenado Baron with REP and F33A with REP mostly). I get to the IAF in NAV mode, the plane follows the horizontal path without any problems. I descend to the published intercept altitude and then arm APP mode on the autopilot. I see the G/S indicators moving down, but when the plane should start to descend to follow the G/S it just stays in ALT HOLD mode.

On one occasion the plane did start to descend when it should, but instead of following the G/S, it kept on pitching down eventually reacing 4000 ft/min vertical speed.

Does anyone have any idea what's wroing here?

[RXP 2,336]

Hi,

Was this working fine prior the last week?

Which XPlane version are you running: the latest official release version, or the latest beta version?

Did it started to fail roughly around the time you'd have updated XPlane to the latest beta version?

[SimPilotNL 3]

I am running the latest release version.

I wish i knew when it happened exactly. But my best guess it either started around the time I updated xPlane to the latest version, or when I updated the GTN750 to the latest version.

I know that a couple of weeks ago (i haven't been flying much due to crazyness at work) it worked just fine.

[RXP 2,336]

This sounds like the latest XPlane version (which is a beta if I'm not mistaken) is maybe causing this then. Can you try reverting back to the latest official RELEASE version instead?

[SimPilotNL 3]

I guess I wasn't clear :). I am running the latest release version of xPlane.

The problems started when I updated from the previous release version of xPlane to this one. Or maybe when I updated the GTN750 to the latest version, im not exactly sure.

But to eliminate the xPlane side, I will try to find time to do a flight this week using the xPlane Garmin unit to see if I have the same problems there. I'll keep you posted!

[SimPilotNL 3]

So, yesterday I took my Airfoillabs C172 out of the hangar and flew a LPV approach using the default Garmin unit in the plane. This time the glideslope was picked up perfectly. So it seems my problem is indeed somehow related to the Reality XP unit.

As soon as I have the time, I will fly exactly the same approach in the same Airfoillabs C172 using the GTN750 to see what will happen there (I'm expexting my plane to stay in ALT HOLD mode which is the problem I've seen lately and described above).

Once I've done that testflight, I'll edit this post with my findings.

[SimPilotNL 3]

Repeated the same flight with the same plane and same approach. This time using the GTN750 though. When I enabled it, xPlane immediately crashed to desktop (I get that almost every time i enable or disable the GTN unit).

Second attempt I could swtich it on though and I tried the approach. Again the autopilot just stayed in Altitude Hold mode, the plane did not start a descent to follow the glideslope.

[Real2Sim 3]

The issue is not from the GTN. I've done several RNAV LPV approaches today and everything worked nice ^^

[RXP 2,336]

I just want to make sure bat this: the latest release version is 11.20:

https://www.x-plane.com/2018/05/x-plane-11-20-final-released/

all other newer versions are 'beta' and could break any plugin.

[SimPilotNL 3]

xPlane version 11.21r2

I guess I'll have to open another topic asking how the <bleep> this got installed as I do not have the option to use beta's checked. Also I have no idea how to roll back. I guess this might be an opportune moment to just reinstall everything.

Sorry for causing this trouble, I really thought I was on the latest release version.

 

[RXP 2,336]

11.21 should've fine though otherwise I'd guess there would be much more similar reports in the forum. Otherwise, you might want to search for conflicting plugins, starting with moving out all plugins to a different folder, testing if this cures the issue, then reintroducing the plugins one by one until finding the culprit.

[SimPilotNL 3]

Ok, so 11.21 is the latest (I really got confused for a moment haha).

I already disabled xEnviro1.9 as I saw other problems reported with that plugin. I don't have a lot of them, so that is another test I will do. If all fails, I will just reinstall xPlane with Realty XP as the only plugin.

Don't get me wrong, I love the GTN750 unit! 😃

[RXP 2,336]

Hi, have you made progress on the re installation?

[SimPilotNL 3]

Due to very busy times at work and the extreme temperatures across Europe, it took way longer than expected.

I have now reinstalled X-Plane with only 1 plugin (that I cannot live without), X-Camera. I have the Airfoillabs C172, the Carenado Baron B58 with REP and the Carenado Bonanza F33A with REP installed. Also removed the complete Reality XP installation and reinstalled that.

Performing my first test flights right now. The GTN750 does not show up in the F33A virtual cockpit (I understood that is an officially supported feature?) and I cannot find how I fixed that last time. When I have figured that out (could take some time with above 30C temperatures here) I will be trying the LNAV approaches again.

 

[SimPilotNL 3]

Got the GTN750 working in the Bonanza F33A using a .ini file from the forums here.

First test flight done. Appproach loaded and activated in the GTN750, AP on, APP mode selected. The plane turns perfectly to intercept the lateral path to the runway. I see the G/S indicators moving on the HSI. The plane however does not start to descend, it just remains in ALT HOLD mode.

I am starting to think that either I have some setting wrong, or I am doing something wrong (although it has worked before).