APPENDIX C
Troubleshooting Q & A
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190-00356-00 Rev B
flag for the active-to waypoint. If an external course in-
put 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
Section 5 - Flying the Missed Ap-
proach
for an example using the OBS key.
One application for the
OBS
key is holding patterns.
The
OBS
key is used to suspend waypoint sequencing and
select the desired course along 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 sequenc-
ing after one time around the holding pattern. A “SUSP”
annunciation will appear directly above the
OBS
key (see
illustration left) to indicate that automatic waypoint se-
quencing is temporarily suspended and course selection
is not available. If more than one trip around the hold-
ing pattern is desired, press the
OBS
key to again suspend
waypoint sequencing. An example of this operation is an
approach which begins with a holding pattern at the ini-
tial approach fix (IAF).
Section 5 - Flying an Approach with
a Hold
for more information on the “SUSP” annunciation
and approaches with holding patterns.
When should I use the OBS key to return to auto
sequencing, and what happens when I do?
The most common application for using the
OBS
key
is the missed approach. The 400W-series unit will suspend
automatic waypoint sequencing (indicated by a “SUSP” an-
nunciation directly above the
OBS
key; see right) when
you cross the missed approach point (MAP). This prevents
the 400W-series unit from automatically sequencing to
the missed approach holding point (MAHP). If a missed
approach is required, press the
OBS
key to return to au-
tomatic waypoint sequencing and sequence the approach
to the MAHP. See
Section 5 - Flying the Missed Approach
for
more information on missed approaches.
Why won’t my unit automatically sequence to the next
waypoint?
The 400W-series unit will only sequence flight plan
waypoints when automatic sequencing is enabled (i.e.,
no “OBS” or “SUSP” annunciation directly above the
OBS
key). For automatic sequencing to occur, you must also
cross the “bisector” of the turn you are navigating. The
bisector is a line that bisects the angle formed by two flight
plan legs; it passes through the waypoint common to both
legs.
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