Controls/Indicators and Functions (Pilot's
HSI, fig. 3-10).
Distance display. Provides digital dis-
plays of DME/TACAN or INS waypoint distance.
TACAN distance is displayed in 1/10 mile incre-
ments. INS distance to waypoint is displayed in
whole mile increments. The display will show dashes
when the distance input data is invalid or absent.
Rotating heading (azimuth) dial. Dis-
plays gyro stabilized magnetic compass information
on a dial which rotates with the aircraft throughout
360 degrees. The azimuth ring is graduated in 5
(3.) Lubber line. Fixed heading marks
located at the fore (upper) and aft (lower) position.
(4.) HDG flag. Indicates loss of reliable
(5.) Heading bug. The notched orange
heading bug is positioned on the rotating heading
dial by the heading knob, to select and display a pre-
selected compass heading. Once set to the desired
heading, the heading bug maintains its position on
the heading dial. The difference between the bug
and the fore (upper) lubber line index is the amount
of heading select error applied to the flight director
computer. In the heading mode the ADI will display
the proper bank commands to turn to and maintain
this selected heading.
(6.) Course display. Provides a digital
readout of selected magnetic course.
(7.) Course pointer. The yellow course
pointer is positioned on the heading dial by the
remote course knob, to a magnetic bearing that coin-
cides with the selected course being flown. The
course pointer rotates with the heading dial to pro-
vide a continuous readout of course error to the
(8.) Bearing pointer. Indicates ADF or
NAV relative bearing as selected by the bearing
pointer source switch.
(9.) ADF annunciator. When illuminated,
indicates ADF bearing information is being dis-
(10.) Bearing pointer source switch. The
bearing pointer source switch, located on the pilots
HSI, provides for selecting between ADF or NAV
bearing information as presented by the bearing
pointer. Each push of the select switch alternates
selection of ADF or NAV. Upon power-up or fol-
lowing long-term power interruption, NAV is dis-
NAV annunciator. When illuminated,
indicates NAV bearing information is being dis-
(12.) NAV flag. Indicates loss of VOR,
TACAN or INS information, or unreliable naviga-
(13.) Compass synchronization annuncia-
tor. The compass synchronization annunciator con-
sists of a dot and X symbol display. When the com-
pass system is in the slaved mode, the display will
oscillate between the dot and X symbol, indicating
the heading dial is synchronized with a gyro stabi-
lized magnetic heading.
(14.) Course deviation dots. In VOR or
TACAN operation, each dot represents 5 degree
deviation from the centerline (± 10 degrees). In ILS
operation, each dot represents 1 degree deviation
from the centerline. In INS operation, each dot rep-
resents 3.75 nautical miles deviation from center-
(15.) Aircraft symbol. The fixed miniature
aircraft symbol corresponds to the longitudinal axis
of the aircraft and lubber line markings. The symbol
shows aircraft position and heading with respect to
a radial course and the rotating heading (azimuth)
Course deviation bar. The course devi-
ation bar represents the centerline of the selected
VOR, TACAN, INS or localizer course. The minia-
ture aircraft symbol pictorially shows actual aircraft
position in relation to this selected course.
VERT flag. Covers glide slope pointer
when not receiving glide slope information.
(18.) Glide slope pointer/scale. The glide
slope pointer displays glide slope deviation. The
pointer is in view only when tuned to a localizer fre-
quency. If the aircraft is below glide slope path, the
pointer is displayed upward on the scale. Each dot
on the scale represents approximately 0.4 degree dis-
To-from pointer. The to-from pointers
aligned on the course pointer, are located 180
degrees apart. One always points in the direction of
the station, along the selected VOR radial or
towards the INS waypoint.
(20.) Navigation source annunciators. Five
different annunciators display navigation data
sources. They are: TAC for TACAN, GPS (not
used), INS, NV2 for VOR 2, NV1 for VOR 1. WPT
indicates arrival at INS waypoint.
Course knob (located on the pedestal).
Positions the course pointer.