Selector Switch. Pressing the navigation mode push-
button selector switch, placarded NAV, selects the
navigation mode. When the NAV mode is engaged,
the flight director commands roll attitudes necessary to
track the course selected on the EHSI. Upon
selection, the NAV mode engages either NAV ARM or
NAV capture, depending upon the aircraft's proximity
to the selected course and its closure rate. While any
conjunction with NAV ARM to provide intercept
sequences cancels the coexisting mode. If the
aircraft's deviation from the selected course centerline
is sufficiently small, or if the rate of closure with the
new course is sufficiently high, the flight director
initiates the NAV capture sequence immediat ely.
(d) Navigation Mode Arm Annunciator.
The navigation mode arm annunciator, placarded NAV
ARM, illuminates to indicate that the navigation mode
has been selected and is armed.
Selector Switch. Pressing the approach mode push-
button selector switch, placarded APR, selects the
approach flight director mode. The approach mode is
similar to the navigation mode with regard to arm,
capture, and track operations.
engages in either the approach arm or capture mode,
depending upon the aircraft's closure rate and
proximity to the selected course. Due to the
heightened sensitivity of the deviation display in the
approach mode, the flight director may initiate turn
commands before the course deviation indicator
displays less than a full scale deflection. Selecting the
approach mode after the aircraft has already passed
the point at which approach capture normally would
begin may result initially in course overshoot due to
the flight director's roll command limits.
between front and back course approaches. Front
course/back course selections are determined by the
relative angle between the aircraft's heading and the
course selected on the EHSI. Intercept angles of
between 0 and 105 will cause the flight control
system to select the ILS front course. Angles of
between 106 and 180 will cause the flight director to
command back course interception and tracking.
It is essential that the course selection
arrow on the EHSI always be aligned with
the ILS front course. Failure to align the
course arrow properly may result in
selection by the flight control system.
The flight director automatically engages the
glideslope arm, capture, and track sequences during
ILS front course approaches. Glideslope coupling is
inhibited during back course procedures.
Any horizontal tracking mode may be employed
automatically upon initiation of approach capture and
(f) Approach Mode Arm Annunciator.
Illumination of the approach arm mode annunciator,
placarded APR ARM, indicates that the approach
mode has been selected and is armed.
(g) Flight Director Mode Push-Button
Selector Switch. Pressing the flight director mode
push-button selector switch, placarded FD, initiates
flight director functions independently of the autopilot
or yaw damper. The flight director will engage roll
attitude hold and pitch attitude hold and the command
bar will come into view synchronized to the current
aircraft attitude. Roll attitudes of less than 2 will
revert to wings level flight.
It is not necessary to press the flight
director key prior to selecting another
flight director mode. Selecting any flight
commands in that mode.
Pressing the flight director key a second time will
disengage the flight director.
The flight director will not disengage if the
autopilot is in use.
(h) Flight Director Mode Annunciator.
Illumination of the flight director mode annunciator,
placarded FD, indicates that the flight director mode
has been selected and is engaged.
(i) Not used.
(j) Not used.
(k) Not Used.