SERVO ACTUATORS
The pitch and roll servos position the eleva-
tors and ailerons in response to commands
from the autopilot. The autopilot then uses
the secondary pitch trim system to zero pitch
servo effort. The autopilot does not trim in the
roll or yaw axis.
Although the yaw damper circuit card is lo-
cated along with the autopilot card within the
right IC-600, it performs the yaw damping
function independent of the autopilot. When
the yaw damper is engaged, the yaw servo is
energized to position the rudder in response
to yaw rate information from the AHRSs.
The pitch, roll and yaw servos are each con-
nected through electrical clutches to capstan
drive mechanisms which are connected via
cables to the respective flight controls. The
clutches on the pitch, roll and yaw servos are
energized closed when the autopilot is en-
gaged. Only the clutch on the yaw servo is
energized closed when the yaw damper is en-
gaged without the autopilot. The YD can be
engaged independent of the AP but the AP
cannot be engaged without the YD. The
clutches are de-energized open when the au-
topilot and yaw damper are disengaged. The
pitch and roll servo clutches are also depow-
ered open when the Touch Control Steering
(TCS) button is held depressed or the Control
Wheel Master Switch (MSW) is depressed.
The TCS button is the upper switch on the in-
board horn of each control yoke and the MSW
is the lower switch on the outboard horn
(Figure 16-47).
AUTOPILOT/YAW DAMPER
CONTROLS AND OPERATION
General
The autopilot and yaw damper are engaged
on the FGC (Figure 16-46) using the AP and
YD buttons. When they are engaged, the green
vertical bar on the switches is illuminated.
AP/YD Annunciation
At the top center of the PFDs is a field dedi-
cated to flight director and autopilot annun-
ciation (Figure 16-31). A horizontal arrow
appears between the flight director vertical
and lateral mode annunciators. This arrow
points left or right, as selected on the FGC XFR
switch, to indicate which flight director the au-
topilot will couple to when engaged. It also in-
dicates which flight director has priority when
the AP is not engaged. This arrow is a repeater
of the arrows on either side of the FGC XFR
switch.
Just below the arrow is a line reserved for au-
topilot, yaw damper and rudder boost annun-
ciation. A green “AP” and “YD” appear when
the autopilot and/or yaw damper is/are en-
gaged. Other annunciators related to the AP,
YD and RB that may appear in this area are AP
T E S T ( a m b e r ) , A P FA I L ( a m b e r ) , T C S
(white), AP (green, amber or red), YD (green
or amber), RB (green or amber), and FD FAIL
(amber).
The AP/YD/RB does a power up self-test
when power is turned on. “AP TEST” an-
nunciates during the self-test. If the test
passes, there is no annunciation until the AP
or YD is engaged. If the self-test fails, an
amber “AP FAIL” annunciates. The crew can
attempt to correct a failed test by checking the
AFCS SERVOS circuit breaker in and cycling
the IC/SG 2 circuit breaker on the copilot’s
CB panel.
When the autopilot is engaged, “AP” and “YD”
are annunciated in green. “RB” will only an-
nunciate in green when it becomes active
(RUDDER BOOST switch – ON, a force > 25
pounds rudder pressure applied by pilot and/or
copilot, airspeed less than approximately 180
knots, and flaps are greater than 3°).
When the AP or AP and YD are disengaged by
the crew, an aural alert (cavalry charge) sounds
once. “AP” or “AP” and “YD” also turns amber
and flashes for 5 seconds. If the yaw damper
is not disengaged, the green “YD” remains
displayed.
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
16-79
FOR TRAINING PURPOSES ONLY
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