b. Controls and Indicators - Pilot's HSI.
(1) Pilot's HSI (fig. 3-10).
The rotating heading dial, which
rotates with the aircraft through-
out 360 degrees, displays gyro
stabilized magnetic compass in-
formation. The azimuth ring is
graduated in five-degree incre-
Indicates heading selected by
This pointed fixed index mark
aligns with the aircraft symbol to
indicate aircraft magnetic head-
ing on the compass card.
Indicates VOR or TACAN radi-
al course selected by COURSE
Indicates that the heading infor-
mation displayed is invalid and
should not be used.
Provides a digital readout of the
Two to-from pointers are situat-
ed 180 degrees apart. The one
which is visible points toward
the station along the selected
The NAV flag indicates that the
information derived from the se-
lected navigational beacon is in-
valid and should not be used.
The yellow course arrow is posi-
tioned on the heading dial by
the course knob to select a mag-
netic bearing that coincides with
the desired VOR/TACAN radial
or localizer course. Like the
heading marker, the course ar-
row rotates with the heading dial
to provide a continuous readout
of course error to the computer.
When one of the radio modes is
selected, the vertical command
bar in the flight director will dis-
play bank commands to inter-
cept and maintain the selected
A fixed aircraft symbol corre-
sponds to the longitudinal axis
of the aircraft and lubber line
markings. The symbol shows air-
craft position and heading with
respect to a radio course and the
This bar represents the center-
line of the selected VOR or lo-
calizer course. The aircraft sym-
bol shows pictorially, actual
aircraft position in relation to
this selected course.
The heading marker is posi-
tioned on the rotating dial by
the heading knob and displays
preselected compass heading.
The heading marker rotates with
the heading dial so the differ-
ence between the marker and the
fore lubber line index is the
amount of heading error com-
puter. In the heading mode, the
flight director vertical command
bar will display the required
bank commands to bring the air-
craft onto and maintain the se-
In VOR operation, each dot rep-
resents five degrees deviation
from centerline. In ILS opera-
tion, each dot represents one de-
gree deviation from centerline.
In INS position, each dot repre-
sents 3.75 NM linear deviation.
Indicates that the information
displayed by the glideslope
pointer is invalid and should not
Indicates deviation from correct
glideslope during ILS approach.
Azimuth marks are fixed at 45°
bearings throughout 360 degrees
of compass card for quick refer-
(2) Pilot's VOR Switches (fig. 2-28).
Selects desired source of data for
display on pilot's HSI and input
to autopilot flight computer.
Selects data from VOR I system.
Selects data from VOR 2 system.
Selects data from TACAN sys-
Selects data from INS.