4. Realignment - INS shut-
5. Position update. Recom-
mended if time is not avail-
able for realignment.
Perform position update using parking
coordinates in accordance with proce-
dure: Insertion of Geographic Waypoint
Coordinates. If parking coordinates are
not available, proceed as follows:
Continue operation in NAV, if INS accu-
racy appears acceptable.
Perform position update using best esti-
mate of parking coordinates.
6. Downmoding to standby:
Mode selector - STBY.
INS can be downmoded to standby opera-
tion which will maintain navigation unit
at operating temperature with gyro wheels
running. INS is downmoded to standby as
Do not leave INS operating unless aircraft
or ground power and cooling air are avail-
able to system.
7. Shutdown: Mode selector -
N O TE
INS will retain inertial present position
data computed at time INS is down-
moded. This value is compared with pres-
ent position inserted for next alignment
and difference is used to determine azi-
muth gyro drift rate.
e. Abnormal Procedures:
General. INS contains self-testing fea-
tures which provide one or more warning indica-
tions when a failure occurs. The WARN light on th
CDU provides a master warning for most malfunc-
tions occuring in the navigation unit. Malfunctions
in the MSU or CDU will normally be obvious
because of abnormal indications of displays and
lights. A battery unit malfunction will shut down
INS when battery power is used.
(2.) Automatic INS shutdown.
(a.) Overtemperature. An overtemp-
erature in navigation unit will cause INS to shut
down (indicated by blank CDU displays) when
mode selector is at STBY or ALIGN during ground
operation. The WARN light on CDU will illuminate
and will not extinguish until mode selector is rotated
to OFF. The cooling system should be checked and
corrected if faulty. If cooling system is satisfactory,
navigation unit should be replaced.
(b.) Low battery charge. A low bat-
tery unit charge will cause INS to shut down when
INS is operating on battery unit power. Both WARN
light on CDU and BAT light on MSU will illumi-
nate 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 indica-
tions. 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 oper-
ator sufficient information to take action.
WARN light illuminated.
Take the following action:
If action codes 01, 02,
03, 04, 05 are displayed
- See table 3-2.
b. No action or malfunc-
tion codes displayed -
Improper displays -
Indicates NU computer
2. WARN light extinguished. If
CDU displays are blank,
incorrect or frozen - CDU
failure is indicated.