Glideslope Mode (GS)
Glideslope Mode requires a valid GPS position.
Glideslope Mode is available for LOC/ILS approaches to capture and track the glideslope. When Glideslope Mode is armed (annunciated as ‘GS’ in white), LOC Approach Mode is armed as the lateral flight director mode.
Once LOC becomes the active navigation source the localizer can be captured, provided the following conditions are met:
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A valid ILS frequency is tuned on the NAV radio.
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A glideslope signal is being received.
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The active waypoint is the FAF or a subsequent waypoint.
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Vertical deviation is valid.
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The CDI is at less than full-scale deviation.
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Automatic sequencing of waypoints has not been suspended (no ‘SUSP’ annunciation on the HSI).
For LOC-only approaches (i.e., no glideslope provided/available), another vertical mode may be selected (e.g., VS or ALTV) for the autopilot to fly a stabilized approach. For ILS Approaches, if the pilot wants to fly the non-precision LOC Approach without capturing the glideslope, pressing the NAV Key instead of the APR Key will prevent glideslope capture. Again, another vertical mode may be selected to fly a stabilized approach.
