NAV mode refuses to engage unless in VLOC1 and tuned into VOR station.
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Happening more and more to me, following the magenta line fine but then after putting in an Approach into the GTN750 the NAV mode drops out and cannot reactivate it. Tried everything I can think of but it refuses to engage. Cannot then fly the approach on GPS.
What is causing this.
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I'm only familiar with the PMS50 implementation of the GTN 750, but this sounds like might what happen if when you put in a localizer or ILS approach you select "load and activate," which I believe will change the CDI selection from GPS to VLOC. The way to fix it is to select "load approach" instead. If you do activate it and want to return to following the magenta line, you'll need to switch back to GPS on the CDI selector.
If it's not that, some more details would be helpful, or some screenshots or video.
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Na, that means having to load another flight and hope that it happens again whilst constantly recording it all. I can safely say I didn't select load and activate. HSI source was set to Nav1, I never change it. The AP was happily following the magenta line until it hit a discontinuity that I noticed had crept in when I added the approach.
I then asked it to do a direct to the next waypoint when it all went ass up. It wasn't following that direct to. Thats when I noticed NAV mode had died. Couldn't get it back. Cycled the Avionics switch, nup. Switched to VLOC and tuned into a nearby VOR, and NAV mode activated ok. Back to GPS mode and the NAV led just went out.
After that I switched back to VLOC, manually dialed in the ILS and flew the final approach in that mode, all fine.
This has happened twice in the past two days after returning from two weeks flying the A2A Comanche to this bird. Don't know what else to add to this post.