Unable to change Nav Source GTN 750

[android772000]

As the title states. I'm new to the aircraft so probably user error, but I cannot get the HSI to display GPS course or range. The GPS/VLOC button on the GTN750 have no effect. However, the CDI button on the 530 seems to switch sources for the FO HSI.

 

Also. The Autopilot does not seem to track the flight plan in heading GPSS mode. I assume this is related to my first stated issue. Thanks for any help!

[tkyler]

I note you mention both a 750 in the title, but a 530 ...and I do not provide a 750/530 panel combo, so I assume you've tried multiple flights/configs, which means settings could have been differing between flights.   So...I'll  just ramble here a bit in general in case you find a useful nugget of info.   I am by no means a GTN750 expert, but IIRC, it still interfaces with default XPlane GPS behaviors.  Also,

4 hours ago, android772000 said:

....I cannot get the HSI to display GPS course or range.

The HSI does not display any GPS information, except for the CDI needle deflection when the GPS CDI button is set to 'GPS' and a GPS leg is active.    So no course or range information related to a GPS waypoint/plan is displayed.  The HSI only displays course/distance information from radio nav aids, i.e. VORs/ILSs.

I'm not fully sure of your navigation config regarding the GPS/VLOC issue, so I'll just speak generally.   This button only changes the CDI needle signal source on the HSI, and so won't do anything unless (in the case of VLOC mode) you are tuned to / receiving from a navaid....and (in the case of GPS mode), you have an active flight plan leg.  I'm not sure if you were tuned to navaid when you tried the GPS/VLOC button, or had entered a flight plan in the GPS and were on an active leg.  Either/or, the only thing you'd observe from pressing this button, assuming you were tuned into to a signal/active leg is the CDI needle on the HSI move a bit.

4 hours ago, android772000 said:

The Autopilot does not seem to track the flight plan in heading GPSS mode

Again, not knowing your full config, I couldn't say what's going on here, but I can say its not related to the GPS/VLOC button at all.  This has zero bearing on the autopilot tracking and engagement.  For practical purposes, only the GPSS button really changes the "SOURCE" signal the autopilot follows.

I've never seen the autopilot not follow a GPS flight plan in GPSS mode when 1) AP is engaged, 2) a GPS flight plan leg is active and 3) the GPSS button is in GPSS mode.  With these three items, the aircraft has always tracked the GPS flight plans for me.  Not seeing the entirety of your cockpit and settings, I couldn't comment exactly what you were seeing.

-tkyler

 

[android772000]

First of all thank you for the response and I apologize about the confusion, I could have given a couple more details. 

 

So in the MU2 preferences menu I have GTN750 selected. So it sounds like I'm getting this wrong, but I thought that the GPS screen below the GTN750 display was the 530. I do not know what to call that display. So whatever that is, it is clearly nav 2. So that being said I can confirm the CDI needle on the FO side of the aircraft does behave as I would expect, and how you explained. It functions as  I would expect with a VOR station, and when I hit the CDI button on that lower GPS unit, it displays deviation from the GPS flight plan on that unit. I just now for the sake of troubleshooting confirmed this by programing in a nearby waypoint, pulling up the Xplane map and clicking and dragging my plane back and forth, watching the needle deflect left and right.

 

I cannot replicate this on the captains side using the GTN750. in VLOC mode it behaves properly, but when I hit the CDI button and switch to GPS source, I cannot get needle deflection not matter what I do. I put in direct to the same waypoint I used to troubleshoot the FO side and moved the airplane around just as I did, and I get no needle deflection. 

 

And with the autopilot issue, I still believe it is related to this other issue. The last flight I did were I troubleshot it just a little bit, I noticed it kept just turning me off course by like 90 degrees, after being directly on course per the flight plan. Happned at different phases of flight.  

 

Thanks again for the help!