3-40 Change 3
Figure 3-19. EHSI Failure Annunciators (Red)
c. Autopilot Self-Disconnection Fault Messages.
The pilot can investigate the cause of an inflight autopilot
disconnection by depressing the SBY button on the flight
director mode selector for more than 5 seconds. The
altitude preselector display will be disconnected from the
digital air data computer and connected to the autopilot.
A numerical fault code will appear on the altitude pres-
elector display. Table 3-4 provides an explanation of fault
codes. Subsequent pushes on the SBY switch on the
flight director mode selector will yield additional fault
codes or dashes, which indicate the end of the error code
log. When the dashes appear in the display, the altitude
preselector display will again be reconnected to the digi-
tal air data computer. Fault messages are displayed as
a letter code followed by a three digit number. Ignore the
last digit of the number, which will be a zero. Table 3-4
describes fault codes.
If the autopilot was disconnected as a result of the
fault, depressing the AP DISC button on the control
wheel will allow the autopilot to be re-engaged, provided
the failure no longer exists.
d. Digital Flight Control System Performance/Oper-
ating Limits. Table 3-5 contains the digital flight control
system performance and operating limits.
e. Yaw Damper. The yaw damper computer provides
basic yaw damper functions with or without the autopilot.
When the autopilot is engaged turn coordination is ac-
tive. Yaw damper mode is active when either the YD or
AP ENGAGE button on the autopilot controller is se-
f. Rudder Boost. The yaw damper computer also
provides rudder assist (boost) in the event of an engine
failure. The amount of assist provided is dependent upon
airspeed and engine power differential. The boost func-
tion is armed when the rudder boost switch located on the
pedestal extension is set to the RUDDER BOOST posi-
g. Autopilot Controller (PC-400). The autopilot con-
troller (fig. 3-21), provides a means of engaging/disen-
gaging the autopilot and yaw damper as well as manually
controlling the autopilot through the turn knob and pitch
wheel. Whenever the autopilot is engaged, it will fly basic
roll and pitch hold or the selected lateral or vertical flight
(1) Pitch Wheel. Rotating the pitch wheel with the
autopilot engaged will result in a change in pitch attitude
proportional to the amount of rotation and in the direction
of wheel movement. Movement of the pitch wheel cancels
only altitude hold (ALT HOLD) or altitude select capture
(ALT SEL CAP). With the vertical modes of vertical speed