TM 55-1510-222-10
purpose control. When the knob is pressed inward, the
TEST switch function is engaged. When the knob is
rotated to either the AUTO or MAN setting, the control
serves as a selector between those modes.
(a) AUTO. Selects automatic leg switching
mode. Computer switches from one leg to the next
whenever way-point in TO side of the TO-FROM
display is reached.
(b) MAN. Selects manual leg switching mode.
Pilot must make way-point changes manually.
(c) TEST. When pressed, performs test of INS
annunciators and displays, remote annunciators and
indicators controlled by INS, and computer input/output
operations.
Used with other controls to activate display of
numerical codes denoting specific malfunctions and
resets malfunction warning circuits.
During
alignment,
activates
the
HSI
test.
Continued pressing of switch provides constant INS
outputs to drive cockpit displays in a predetermined
fashion.
NOTE
The INS can provide test signals to
the
Horizontal
Situation
Indicator
(HSI)
and
connected
displays.
Pressing TEST switch during STBY,
ALIGN, or NAV modes will cause all
digits on connected digital displays to
indicate 8's and illuminates the HSI
WAYPOINT and ALERT annunciators.
Additional
HSI
test
signals
are
provided when INS is in ALIGN and
the data selector is at any position
other than DSRTK/STS. Under those
conditions, pressing TEST switch
causes the HSI to indicate heading,
drift angle, and track angle error, all at
0° or 30°. At the same time, cross
track deviation is indicated at 3.75
nautical miles (one dot) right or left
and INS controlled HSI flags are
retracted from view.
Output test signals are also supplied to the
autopilot when INS steering is selected. Rotating
AUTOMAN switch to AUTO and pressing TEST during
align furnishes a 15 left bank steering command. A
15° right bank steering command is furnished when the
AUTO/MAN switch is set to MAN.
(12) TO-FROM display. Display numbers
defining way-points of navigation leg being flown or, in
the case of a flashing display, displays TACAN station
being used.
Way-point numbers automatically change each
time a way-point is reached. Unless flight plan changes
during flight, the automatic leg switching sequence will
always be 1 2, 2 3, 3 4...8 9, 9 1, 1 2, etc.
(13) Data selector. Selects data to be displayed
in data displays or entered into INS. The rotary selector
has 10 positions. Five positions (L/L POS, L/L WY PT,
UTM POS, UTM WY PT and DSRTK/STS) also allow
data to be loaded into data display then inserted into
computer memory.
(a) TK/GS. Displays aircraft track angle
in left display and groundspeed in right display.
(b) HDG/DA. Displays aircraft true
heading in left display and drift angle in right display.
(c) XTK/TKE. Displays cross track
distance in left display and track angle in right display.
(d) L/L POS. Displays or enters present
aircraft position latitude in left data display and
longitude in right data display. Both displays indicate
degrees and minutes to nearest tenth of a minute. This
position also enables the insertion of present position
coordinates during alignment and present position
updates.
(e) L/L WY PT. Displays or enters way-
point and TACAN station data, if used in conjunction
with the way-point/TACAN selector. This position will
also cause display of inertial present position data when
the HOLD key is illuminated.
(f) DIS/TIME. Displays distance from
aircraft to TACAN station or any way-point, or between
any two way-points in left display. Displays time to
TACAN station or any way-point, or between any two
way-points, in right display.
(g) WIND. Displays wind direction in left
display and wind speed in right display, when true
airspeed is greater than the air data system lower limit
(80 KIAS).
(h) DSRTK/STS. Displays desired track
angle to nearest degree in the left data display, and INS
system status in right data display.
(i) UTM POS. Displays or enters aircraft
position in Universal Transverse Mercator (UTM)
3-45
