HSI Operation
FlightDEK-D180 Pilot’s User Guide 6-5
up and in line with the heading pointer keeps the aircraft on course. This indicator is fixed to the rotation of th
DG, so it is easy to see which way you must turn to get on course. The course indicator is only present when
you are tuned to a VOR or a localizer. If the NAV radio indicates that you are not currently tuned to an active
frequency, this indicator is not displayed. The direction of this course is set externally using the knob that is on
the SL-30 when in VOR mode. When in ILS mode, the SL-30 disables the OBS knob, and thus you must use
the soft keys below the HSI in order to set the course.
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When using the HS34 you can set the OBS using the COURSE knob. When properly configured, the HS34
sends course information to the NAV radio, just like a mechanical HSI or CDI does. When using an SL-30, the
HS34’s knob must be used to set the OBS; the SL30’s OBS is overridden by the course information sent out by
the HS34.
3. Course Deviation Indicator (CDI). When tuned to a VOR, the CDI indicates how far to the
left or right of your selected radial you are. Full scale deviation indicates ten degrees of
deviation from the radial that has been chosen as the course. When tuned to a localizer, full
scale represents 2.5 degrees of deviation. When on course, the course indicator and the CDI
make a solid line, making it easy to see when there is little error in your aircraft’s position.
Unlike a CDI indicator found in basic aircraft, the CDI needle on an HSI rotates with the DG
and course indicator. By turning the aircraft towards the CDI needle you reduce your deviation.
4. To/From indicator. Because an HSI rotates the course line on top of the DG, the to/from indicator
always points TO the physical VOR or localizer transmitter. If it is pointing the same direction as the
arrow at the end of course line, then that is a “to” indication. If it is pointing the opposite direction of
the arrow at the end of the course line, then that is a “from” indication. This data comes from the
to/from flag indicator provided by your Nav radio. In the image above, the to/from indicator is
showing a “from” indication.
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