on the inner ring represents one-half the range setting of
the weather radar.
(2) Navaid position. Navaid position may
be selected for display during map mode. Source of
navaid position markers is selected and annunciated in
conjunction with the associated bearing source and is
(3) Weather. Weather radar information
may be displayed in the partial compass mode.
(4) Off scale arrow. When the heading
marker is rotated out of view (off scale) an arrow on the
compass arc is provided to indicate the shortest direction
of the heading marker.
EHSI Short Range Navigation (SRN) Map
Mode (fig. 3-16). Map mode is selected by depressing
the FULL/MAP pushbutton selector switch on the
display controller until the EHSI is in the MAP mode.
When the map mode has been selected, the
following will occur:
The course pointer and course deviation bar
displays will be removed.
Both bearing pointers will be removed.
A full-scale navigation deviation display and
deviation bar will be present on the bottom of the EHSI
display. This will show the position of the aircraft with
respect to the selected course.
The map mode deviation display functions as a
simple, fixed-card course deviation indicator for VOR or
TACAN data. As long as the aircraft is headed within 90
degrees of the selected course or selected radial, and as
long as the to-from annunciation is correct, the course
deviation indicator (CDI) will be directional; otherwise, it
will display reverse sensing and the techniques required
for reverse sensing will apply.
When the navigation source is a localizer, and
the aircraft has a heading greater than 90 degrees to the
selected inbound localizer course, the CDI will reverse
polarity, but will remain directional.
When VOR or TACAN stations are shown on the
EFIS map, a solid or dashed course line is drawn
through the selected navigation source. The solid line
represents the selected inbound course to the station.
The dashed line represents the selected outbound radial
from the station. If TACAN has been selected as the
NAV source, the identifier will be displayed adjacent to
the navaid symbol. Cross-side navaid identifiers are not
Figure 3-16. EHSI Partial Compass VOR Map Mode