Garmin G3X Pilot's Manual page 293

Selecting Glideslope Mode:
1) EXTERNAL NAVIGATOR: Tune and activate the desired localizer frequency.
2) EXTERNAL NAVIGATOR: Ensure that LOC is the selected navigation source
(use the CDI SRC Softkey to cycle through external navigation sources if
necessary).
3) G3X: Press the ALT/PTCH Softkey to access the autopilot pitch modes
and press AP APPR Softkey. This simultaneously selects LOC and GS
(Glideslope) Modes.
Or:
NOTE: The following procedure is useful for arming the ILS while using the GPS to
fly a procedure turn. Configuration of an external GPS navigation source (i.e., GTN
or GNS Series) is required.
1) EXTERNAL NAVIGATOR: Tune and activate the desired localizer frequency.
2) EXTERNAL NAVIGATOR: Load the approach (LOC, ILS, LDA, SDF, etc) into
the flight plan.
3) G3X: While GPS is still the selected navigation source on the external
navigator, press the AP APPR Softkey to arm LOC and GS (Glideslope)
Modes even with GPS Mode still active. The external navigator will switch
from GPS to VLOC automatically and the G3X will capture the localizer and
then the glideslope.
190-01115-00 Rev. G
Glideslope Mode Armed
Garmin G3X Pilot's Guide
Integrated Autopilot
Glideslope
Mode
Armed
Glideslope
275