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GARMIN GTN 6XX: "VNAV Unavailable" ??

jclark

Well Known Member
Benefactor
Setup: Garmin GTN 625, SL-30 + Trig TT-22 with control head + GRT Horizon 10.1

Problem 1: I get a "VNAV Unavailable: Barometric Altitude Lost" error message on startup.

Curiosity 1: I also was not getting LAT/LON to the Trig for a while until I changed the output format from ADSB +1 BACK to just ADSB on the GTN 625 (feeding the Trig TT-22). Does anyone know why???

Soo ...

Does anyone know what settings work with the combination above?
[I **KNOW** that it works with the GTN 650 + Trig TT-30 + GRT HXr (Legacy)]

I have gone through Garmin/GRT/Trig documentation and for some reason, I must be missing something.
I have called Garmin and I have a call into GRT as well.

FADC 1? Fuel Air Data "Z" (what I have used in the past) format or "S" (which had barometric altitude) or maybe even "D"??

THANKS ... I have already scratched all of my hair off my head. :)
 
Curiosity 1. For going from G420W to Trig I use ‘ADSB+’. There is a ‘+’, but no ‘1’. My guess is Trig reverse engineered that format and is in no hurry to update it.
Problem 1. Like your previous setup, my Hx to G420W uses ‘fuel Air Shadin Z’. Try booting the efis first, wait, then boot the GTN. Maybe the GTN boots faster and immediately sends an error message rather than waiting??
 
Curiosity 1. For going from G420W to Trig I use ‘ADSB+’. There is a ‘+’, but no ‘1’. My guess is Trig reverse engineered that format and is in no hurry to update it.
Problem 1. Like your previous setup, my Hx to G420W uses ‘fuel Air Shadin Z’. Try booting the efis first, wait, then boot the GTN. Maybe the GTN boots faster and immediately sends an error message rather than waiting??

Thanks.

I do in fact, boot the EFIS first and boot GTN (and some other items) after the engine start.
 
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