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 lati-
tude 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 indi-
cate suspect key. Press and release suspect
key several times. To test whether the
keyboard problem is corrected, try press-
ing 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.
CDU BAT indicator light is illu-
Operation on battery is an indication that
there may may be no aircraft power to
blower motor with resultant loss of cool-
ing. 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.
CDU BAT indicator will illuminate for
12 seconds in alignment State 8 (about
5 minutes after turn-on). This is normal
and indicates a battery test is in progress.
No corrective action is required.
During ground operation, it is recom-
mended that operation on battery power
not exceed 5 minutes.
action: (Monitor CDU dis-
CDU selector switch.)
If displays are frozen
(do not change while
data selector is being
rotated) problem is
normally in the naviga-
If displays respond nor-
mally to the data selec-
tor, the problem is nor-
mally absence of 115V
AC power to INS.
(e.) For corrective action: Check to
assure proper settings of following switches and cir-
cuit breakers essential to INS operation:
1. Overhead circuit breaker
panel (fig. 2-26) - Circuit
b. INS CONTROL
d. AVIONICS MASTER
2. Overhead control panel (fig.
2-12): INVERTER No. 1 or
INVERTER No.2 switch -
3. Mission control panel (fig.
#1 INV or #2 INV
switch - ON.
b. Bus cross tie switch -
Mission AC/DC Power Cab-
inet (fig. 2-2): INS AC PWR
circuit breaker - In.
CDU BAT indicator should extinguish
after above corrective action. If it remains
illuminated, INS will eventually shut
down when battery voltage drops below
19VDC. Flight crew
should prepare for shutdown.
(3.) Malfunction indications and proce-
dures: Table 3-3 details the procedure for a Malfunc-
tion Code Check. Table 3-4 lists a number of mal-
function indications which occur under given modes
of operation. Follow procedure given. Table 3-5
details action codes and recommended action. Table