To achieve best accuracy, engine start and
heavy loading activity should be delayed until
entry into NAV mode.
Verify UTM grid coefficients (if UTM coordinates
are to be used).
Data selector (CDU) UTM WY PT.
Observe TO-FROM display is blank. Earth
flatness coefficient appears in left display.
The relative earth radius, in meters, appears
in right display.
These values are retained from turn-
on to turn-on unless changed by
Verify that values correspond to those
required for spheroid being used.
Values for various spheroids are listed
in table 3-1.
(d) If values are correct, return CDU to normal
display mode by momentarily setting data
selector to any position except UTM WY PT.
If values are to be changed, continue with the
The INS geographic position, as read
in L/L displays, will not be affected
by any changes in these coefficients.
(e) Keys"2" or "8" Press to indicate following is
the flatness coefficient. Observe INSERT/
(f) Load earth flatness coefficient by pressing
keyboard keys in sequence. Example: 2 9 4
9 8 = 29498. Observe numbers appear in left
display as keys are pressed.
(g) INSER/ADVANCE pushbutton Press.
(h) Keys"4" or "6" Press, to indicate that the
following load is relative earth radius.
(i) Load relative earth radius by pressing
keyboard keys in sequence. Example: 8 2 0 6
m = 8206. Observe numbers appear in the
right display as keys are pressed.
Zone symbol is to be ignored.
INSERT/ADVANCE pushbutton Press.
Observe INSERT/ ADVANCE pushbutton
(k) Data selector (CDU) UTM POS. Observe
coordinate will reflect values of new spheroid.
Abbreviated INS interface test As required:
indicators will become level during
alignment state "8" and remain level in
all modes until INS is shut down.
Warning indicators for INS attitude
signals from the INS are valid while
attitude sphere display is level.
The INS can provide test signals to the
Horizontal Situation Indicator (HSI) and
connected displays. Pressing TEST
switch during STBY, ALIGN or NAV
mode causes all digits on connected
digital displays to indicate "8's" and the
illuminate. Additional HSI test signals
are provided when INS is in ALIGN and
data selector is at any position other than
DSRTK/ STS. Under those conditions,
pressing TEST switch causes 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.
Change 2 3-51