WAAS = OFF and RAIM check with GTN XI?

[kortopates]

On 3/16/2024 at 1:34 PM, airdogalpha said:

I hope this is the correct thread.  Pls forgive me if is not.     I was flying my TXI, connected to a 750 today on a RNAV rwy 07 CYXX approach.      I joined the IAF at 3000 feet,   roughly nine miles back.    airplane flew it perfectly.   It confirmed LPV,     and captured the glide slope advisory.    The weird thing was the Diamond (advisory gS) was grey the entire way down to minimums, normally this is magenta.   (did it lose WAAS?)     I have never had this before.  I hunted and searched the txi and GTN manual.  Did word searches... I came up with nothing.  Anyone have any idea?         

I am pretty sure your confusing VNAV with advisory glide slope. Remember there is no such thing as advisory glide slope on a LPV which has real glide slope. You would have had VNAV from the IF (or even descending to the IF) and all the way up to the leg leading to the FAF. On the leg leading to the FAF while still showing VNAV, (which is half a magenta diamond with the letter V at the top of the indicator) you’ll start to see the actual glide slope as a full diamond but greyed out since it’s not active. As you follow the VNAV glide slope down to FAF, VNAV half diamond will disappear as you cross the FAF and the glide slope takes over as solid diamond, and you’ll see at the top of the indicator it no longer shows V but G.

Edited March 18, 2024 by kortopates

[PT20J]

In the G3X Pilot's Guide, Rev F, Garmin calls that grey diamond a VDI Preview. I believe it is active when VNAV is active and the GP or GS comes into view, but is not yet active. This would seem to be most useful as a heads up if the GTN Xi Transition to Approach were enabled where VNAV smoothly transitions to the GP or GS. Transition to Approach currently works with the GFC 600 but not the GFC 500. I'm told by Joey Ferreyra that Garmin is working on it for the GFC 500 and the fact that VDI Preview was added to the G3X in, I believe, v9.15, might imply that it will happen. With Transition to Approach disabled per the STC, VNAV terminates at the FAF for LNAV and at the fix before the FAF for approaches with vertical guidance.