Figure 3-22. INS Mode Selector Unit (7883470-011)
Moving to STBY from any other mode: INS operates
as if in attitude reference mode.
(c) ALIGN (ground use only, parked). Moving to
ALIGN from OFF mode: Leveling starts after fast
warm-up heaters are off. Moving to ALIGN from STBY:
Alignment starts if fast warm-up heaters are off.
Moving to ALIGN from NAV mode: INS is not
downmoded, but will allow automatic shutdown if
overtemperature is detected.
(d) NAV. Activates normal navigation mode after
automatic alignment is completed; must be selected
before moving aircraft. Moving to NAV from STBY
mode causes INS to automatically sequence through
STBY and ALIGN to NAV mode, if present position is
inserted and aircraft is parked. NAV mode is used to
shorten time in STBY and to bypass battery test, if
stored heading is valid.
(e) ATT. Activates attitude reference mode. Used
to provide only INS attitude signals. Shuts down
computer and CDU leaving only BAT and WARN
annunciators operative. Once selected, INS alignment
c. Controls/Indicators and Functions, INS Control
Display Unit. (FIG. 3-23).
(1) HOLD key. Used with other CDU controls to
stop present position display from changing, in order to
update position and to display recorded malfunction
codes. Illuminates, when pressed the first time;
extinguishes when pressed second time or when
inserted data is accepted by computer. When pressed
second time, allows displays to resume showing
changing current present position.
(2) ROLL LIM key. Allows selection of Roll
Limited steering mode. Press to select mode, key
annunciators. Roll steering output is limited to 10
degrees. Press second time to exit mode, key
annunciator extinguishes. Roll steering output returns
to normal limit of 25 degrees.
(3) Data display, left and right. Composed of
annunciators which illuminate to display numbers,
directions, and latitude or longitude directions.
(4) INSERT/ADVANCE/HI PREC key. Allows
insertion of loaded data into computer. Enters
displayed data into INS. When pressed before pressing