Garmin G3X Touch Pilot's Manual page 107

Setting up GTN for use:
1) Boot the associated GTN in configuration mode.
2) Select GTN Setup > Navigation Features > Vertical Navigation.
3) Select VNAV.
4) Ensure Transition to Approach is deselected. When deselected, VNAV
guidance will terminate at the waypoint preceding the FAF.
Only the GTN Xi displays VNAV TOD (Top of Descent) and BOD
NOTE:
(Botton of Descent) indications on the G3X Touch.
An altitude constraint in the GTN flight plan is necessary to utilize GTN VNAV.
Altitude constraints are set and changed only on the GTN by pressing the altitude
constraint field next to the waypoint on the flight plan page. This can be verified by
looking at the map on the GTN and see the TOD (Top of Descent) indicated on the
map (see first image below). As you approach this point, the magenta arrow on the
vertical deviation indicator on the PFD will start to come down and the VNAV altitude
constraint should be displayed. As you reach TOD, the magenta arrow will center up on
the vertical deviation indicator.
190-02472-00 Rev. D
VNAV Configuration
Top of Descent Indication (GTN)
Garmin G3X Touch ™ Pilot's Guide for Certified Aircraft
Flight Instruments
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