TM 55-1510-215-10
NOTE
With the HDG SEL mode in operation, subsequent
changes made in the heading bug position will
The flight director (FD) mode must be
immediately cause the command V-bar to call for a turn
activated before the autopilot can be
to the new heading.
engaged.
The HDL SEL mode is cancelled when NAV or
APPR coupling occurs, or whenever the FD or HDG
(2) Autopilot engagement.
mode buttons are depressed.
CAUTION
CAUTION
Prior to autopilot engagement, insure
An invalid heading source (compass
that command V-bar commands are
flag in view) will automatically
satisfied.
disengage the autopilot. The autopilot
may be reengaged; however, only the
The autopilot is engaged by moving the AP switch
vertical modes will be useable.
on the mode controller to the ON position. FLT DIR,
AUTOPILOT will display in the mode annunciator panel
(4) Yaw damp (YD) mode. The yaw damp
controller is located beside the mode controller
mode is automatically engaged.
The autopilot, together with the yaw damp, provides
autopilot is engaged.
Disengagement of YD is
three-axis stabilization, automatic turn coordination, and
accomplished by using the alternate action switch
automatic elevator trim, as well as automatic response to
located on the yaw damp controller. YD may be
all selected flight director commands.
engaged alone or with any flight director mode. Yaw
damp engage status is indicated by a annunciator,
placarded ON, located on the YD controller.
CAUTION
(5) Navigation (NAV ARM and NAV CPLD)
When the autopilot is engaged,
mode. The NAV mode provides visual commands on
manual application of a force to the
the FDI. and deviation guidance on the pilot's HSI to
pitch axis of the control wheel for a
intercept and track a VOR or RNAV course.
period of 3 seconds or more will
result in the autotrim system
operating in the direction to create an
When the NAV button on the mode controller is
opposing force. If the autopilot is
depressed. NAV/ARM will be displayed on the mode
disengaged under these conditions,
annunciator panel and the automatic capture circuit is
the pilot may be required to exert
armed. HDG SEL is retained until capture occurs. The
control forces in excess of 50 pounds
VOR/RNAV course-capture point is variable to prevent
to maintain the desired aircraft
an overshoot. It depends on the angle of intercept and
attitude. This force will have to be
rate that course deviation is changing. Upon capture. a
maintained until the aircraft is
bank command will be displayed on the FDI; HDG (if on)
manually retrimmed.
will be cancelled and NAV/CPLD will be displayed on the
mode annunciator panel. The pilot can manually bank
(3) Heading select/preselect mode (HDG
the aircraft to satisfy the command display which will call
SEL). Prior to selecting the HDG SEL mode, position
for a rollout to level flight when on course centerline to
the heading bug on the pilot's HSI. Depress the HDG
track the course. Crosswind compensation is provided
button on the mode controller, activating the HDG SEL
in the track state.
mode. HDG SEL will display on the mode annunciator
If the NAV mode is selected with the aircraft level
panel (fig. 2-22) and a computed, visually displayed
4-degrees of bank and within three dots of course
bank command will show on the FDI. The command V-
deviation, NAV/ARM will be bypassed and NAV/CPLD
bar on the FDI will deflect in the direction of the shortest
will engage directly. If the autopilot is engaged, the
turn to satisfy the commanded turn to the preselected
aircraft will bank to satisfy the command display and
heading. The aircraft may be manually banked to
rollout on course automatically.
realign the command V-bar and satisfy the command or,
if the autopilot is engaged, the aircraft will automatically
Upon station (or waypoint) passage. an outbound
bank, turn to, roll out, and hold the preselected heading.
course other than the inbound reciprocal can be selected
As the aircraft approaches the selected heading, the
by resetting the NAV course arrow on the HSI. This will
command V-bar will command a rollout to wings level.
Change 5 3-29
