Autopilot/Yaw Damper - BOMBARDIER LEARJET 40 Pilot's Manual

Pilot's Manual
VNV (Vertical Navigation) button — Depressing the VNV button
arms, then captures the FMS pitch steering commands of the FDs if
FMS is selected as the NAV source, the FMS is programmed for a verti-
cal navigation profile, the altitude preselector is set below existing alti-
tude and the aircraft is within the TOD (top of descent) window. When
the VNAV mode is armed, a white VNAV is annunciated on the PFDs
in the FD vertical mode annunciation field and will turn green upon
capture.
ASEL (Altitude Select) knob — The preselected altitude is set via the
ASEL rotary knob on the FGC. The altitude preselect mode provides a
means for FD/AP to climb or descend to a preselected altitude and
then level off and maintain the preselected altitude. The ASEL knob is
used to set the altitude preselect function, and also provides the alti-
tude reference for the altitude alerter function.
ALT (Altitude Hold) button — Altitude hold may be engaged by de-
pressing the ALT button on the FGC. When ALT is engaged, the FD
commands pitch to hold the existing altitude at the time the ALT button
was depressed, or at the ASEL reference altitude if ALT automatically
engages.

AUTOPILOT/YAW DAMPER

The autopilot is a single-channel autopilot which may be coupled to
either flight director. The autopilot function is contained within the #2
IC-600 located in the nose. The IC-600 will fly the aircraft based on the
selected control mode and guidance inputs from the coupled flight di-
rector, via servo control of the elevator, aileron and rudder. When en-
gaged, the autopilot will also automatically command trim changes as
required to alleviate the aerodynamic loading on the elevator (pitch
trim), and will allow control surface commands to be entered via the
control wheel trim switches for the ailerons and elevator. There is also
a Touch Control Steering (TCS) feature which allows the cockpit crew
to manually maneuver the aircraft with the autopilot engaged when
the TCS switch is pressed. The autopilot provides aircraft control in re-
sponse to pitch and roll steering commands from either flight director.
The yaw damper software computes servo commands based on sensor
input data only. The yaw damper control software provides yaw rate
damping that holds rudder force to zero. The servo position reference
is synchronized to zero at engagement and is constantly washed out to
ensure that the steady-state rudder forces are zero. The yaw damper
can be engaged independent of the autopilot but the autopilot cannot
be engaged without the yaw damper.
5-69
PM-132A