pushbutton, any incorrectly loaded data can be
corrected by pressing the CLEAR pushbutton and
loading correct data.
a. Data selector L/L POS.
Observe that, prior to initial load, the INSERT/
ADVANCE pushbutton annunciator is illuminated.
b. To load latitude data Press keys in sequence,
starting with N or S to indicate north or south.
Example: 42° 54.0' North = N 4 2 5 4 0. Observe that
latitude appears in left data display as keys are pressed.
c. INSERT/ADVANCE pushbutton Press.
Observe pushbutton annunciator remains illuminated.
d. To load longitude data Press keys in
sequence, starting with W or E to indicate
west or east.
Example: 87° 54.9' West = W 8 7 5 4 9. Observe that
longitude appears in right data display as keys are
f. Data selector DSRTK/STS. Confirm:
(1) Left data display indicates desired
track angle in computer memory.
(2) Right data display indicates ---84, ---
74, ---64, or ---54, depending on
which alignment state the computer
inserted and computer has advanced
to state 7, present position cannot be
reinserted without downmoding to
STBY and restarting alignment.
g. Data selector (CDU) DSRTK/STS. Observe
left-hand data display indicates the desired
track in computer memory and right data
display indicates status --194-.
If fourth digit from right is blank, a
valid heading has not been stored.
h. Monitor data display for system alignment
state 9 to alignment state 8. Observe right
data display will be ---- 184-.
i. Monitor data display for malfunction codes.
Observe if the 26V 400 Hz power is off, .03184 will
appear in the right data display and WARN annunciator
illuminates. If magnetic compass system is off, .03184
will appear in right data display and WARN annunciator
j. If there are malfunction codes, proceed to
ABNORMAL PROCEDURES in this chapter.
To achieve best accuracy, engine start
and heavy loading activity should be
delayed until entry into NAV mode.
Way-point data and TACAN station
data may be loaded any time after
(3) Verify UTM Grid Coefficients:
1. Data selector (CDU) - UTM WY
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
3. Verify that values correspond to
those required for spheroid being used.
Values for various spheroids are
listed in table 3-2.
4. 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 following steps: