Garmin GNC 420 Pilot's Manual & Reference page 177

What does the O key do and when do I use it?
O
The key is used to select manual (OBS mode) or automatic waypoint sequencing of way-
points. Activating OBS mode (as indicated by an
key) holds your current 'active to' waypoint as your navigation reference and prevents the GPS from
sequencing to the next waypoint. When OBS mode is cancelled, automatic waypoint sequencing
is selected, and the GNC 420 will automatically select the next waypoint in the flight plan once the
aircraft has crossed the present active-to waypoint.
NORMAL (no "OBS" annunciator)
Automatic sequencing of waypoints
Change in HSI does not affect CDI deflection
Always navigates 'TO' the active waypoint
Must be in this mode for final approach course
Whenever OBS mode is active, the GNC 420 allows you to select the desired course to/from a waypoint using the HSI (much like a VOR) and
display a to/from flag for the active-to waypoint. If an external course input is not available, you may select the OBS course on-screen, via a "Select
OBS Course pop-up window. With OBS mode cancelled, the CDI will always display a 'TO' indication for the next waypoint once you've crossed the
active waypoint (provided the active waypoint is not the last waypoint). Refer to page 72 for an example using the
O
One application for the
the waypoint side of the hold. For many approach operations, setting and resetting of waypoint sequencing is automatic. Holding patterns that are
part of an approach will automatically disable waypoint sequencing, then re-enable waypoint sequencing after one time around the holding pattern.
annunciation directly above the
Manual sequencing- 'holds' on selected waypoint
Manually select course to next waypoint from HSI
Will indicate 'TO' or 'FROM' waypoint
Cannot be set for final approach course or published holding patterns
O
key is holding patterns. The
A "SUSP" annunciation will appear directly above the
automatic waypoint sequencing is temporarily suspended and course selection is not available. If more
than one trip around the holding pattern is desired, press the
sequencing. An example of this operation is an approach which begins with a holding pattern at the
initial approach fix (IAF). See page 73 for more information on the "SUSP" annunciation and approach-
es with holding patterns.
O
OBS
key is used to suspend waypoint sequencing and select the desired course along
TROUBLE-
SHOOTING
O
key.
O
key (see illustration left) to indicate that
O
key to again suspend waypoint
APPENDIX
D
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