TM 55-1510-219-10
Table 3-3. Malfunction Indications and Procedures (Continued)
(b)
Low battery charge. A low battery
unit charge will cause INS to shut down when INS is
operating on battery unit power. Both WARN lamp on
CDU and BAT lamp on MSU will illuminate and not
extinguish until the mode selector is set to OFF. The
battery unit should be replaced when this failure occurs.
(c)
Interpretation of failure indications.
It is important to be able to correctly interpret failure
indications in order to take effective action. Failure
indications are listed below under two main categories:
WARN light illuminated, and WARN light extinguished.
Under each of these categories are listed other
indications which will give the operator sufficient
information to take action.
1
WARN light on/off
DISPLAY
MALFUNCTION/ RECOMMENDED
ACTION
Action codes 01,
See Table 3-4.
02, 03, 04, 05
No action or
Indicates computer failure.
malfunction
codes displayed
Improper
Indicates NU computer failure.
displays
2
WARN light off
DISPLAY
MALFUNCTION/ RECOMMENDED
ACTION
CDU displays
CDU failure indicated.
blank, incorrect
or frozen
NOTE
It is not possible to load displays from
the keyboard. A temporary failure of a
numerical
key
may
prevent
data
loading. If a number cannot be loaded
into latitude or longitude displays, after
pressing/ wiggling the key several
times, the cause may be the momentary
hang-up of another key. To identify the
faulty key, rotate the data selector to
DSRTK/STS. The right digit on right
display will indicate suspect key. Press
and release suspect key several times.
To test whether the keyboard problem
is corrected, try pressing any other
numerical key. Its number should now
appear as the right digit. If this test is
successful, press the CLEAR key and
return data selector to original data
loading position. Otherwise, a CDU
failure is indicated.
(d)
CDU BAT indicator is illuminated.
CAUTION
Operation on battery is an indication
that there may be no aircraft power to
blower motor with resultant loss of
cooling. The INS can operate only a
limited time (normally 15 minutes) on
battery power before a low voltage
shutdown will occur. Then, immediate
corrective action must be taken.
3-69
