Flight director mode selector panel -
Select NAV for TACAN navigation
or APR for a TACAN approach.
The EADI will annunciate NAV arm
and capture when appropriate.
The flight control system will perform the capture
and tracking as described for VOR navigation and
(7) Inertial navigation system (INS) steering
mode. Operation in the INS steering mode is similar to
operation in the NAV mode, with the following
Instead of using course error and radio deviation
from the symbol generator, a composite lateral steering
command from the INS through the symbol generator is
Lateral steering command gain is programmed
in the INS.
LNAV is annunciated on the EADI.
Desired track is selected by the INS.
When the NAV pushbutton switch-indicator on
the flight director mode selector panel is depressed,
LNAV will annunciate in green on the EADI. The flight
command computer will use the INS-supplied steering
commands to track the desired course. Bank angle limit
is 22 degrees.
LNAV mode is cancelled by:
Depressing the NAV pushbutton indicator-
selector switch on the flight director mode selector panel.
Selecting go-around mode - Selecting standby
Selecting an alternate ATT, HDG, or NAV
source on the display controller.
(8) Preview and transition mode. A preview
course pointer (magenta) is provided to enable the pilot
to preview data prior to its use. The flight control
computer can be commanded to automatically transition
from tracking the INS to tracking one of the short range
navigation (SRN) sources (VOR, localizer, or TACAN).
One use for this feature is to transition from tracking the
INS to an approach using VOR, localizer, or TACAN.
Set-up for preview course pointer mode is as
switch (display controller) - INS.
NAV pushbutton selector switch
(flight director mode selector panel)
- Depress NAV to capture and track
EADI - Observe that LNAV (green)
Selection of V/L or TCN on the
display controller after the above
three conditions have been met.
The preview course deviation bar will respond to
VOR, localizer, and TACAN signals as appropriate.
Once the previewed navigation source is valid, if
the approach mode (for localizer, ILS, or TACAN) or
VOR approach mode (for VOR) has been selected on
the flight director mode selector, the appropriate LOC,
ILS, or NAV annunciator will be illuminated on the EADI.
When the flight director determines that the
capture point for the previewed mode has been reached,
it will transition the flight director from LNAV mode to the
capture mode of the previewed navigation source. The
preview course pointer will then be removed and the
standard course pointer will be slewed to the previewed
Since INS and TACAN are selected with the
same display controller pushbutton switch, it
is possible to inadvertently reselect the INS
as the navigation source rather than preview
the TACAN navigation source.
(9) Localizer (NAV) mode. The localizer
mode provides for automatic intercept, capture, and
tracking of a front course localizer beam. Prior to mode
engagement, perform the following:
(display controller) - Depress to
select LOC1 or LOC2.
Course pointer (EHSI) - Set inbound
course on heading dial.
desired intercept heading for course
The EHSI will display the relative position of the
aircraft to the center of the localizer beam and the
desired inbound course. With the heading marker set,
the heading select mode can be used to perform the
intercept. Outside the normal capture range of the
localizer signal (between one and two dots on the EHSI),
depressing the NAV or