Control Switches—Control of the autopilot
and the yaw damper is by means of the AUTOPI-
LOT MASTER switch on the pilot’s subpanel
on SNs 23-003 through 23-099. On SNs 24-100
and subsequent, when airplane power is on,
the yaw damper receives power directly through
the AFCS circuit breakers. On 23 models, a
three-position YAW DAMPER ON/OFF YAW
LOCK switch is located on the pilot’s sub-
panel. Yaw lock, when selected, energizes both
servo clutches (motor not running). This main-
tains the rudder position at the pilot’s selected
position for a yaw damper failure. On all model
24 and 25 airplanes, the yaw damper engage/dis-
engage buttons are located on the flight con-
troller.
Wheel Master Buttons—The wheel master but-
tons are momentary switches on all models
(Figure 16-8). When either switch is depressed,
autopilot roll, pitch, and yaw axes disengage.
Maneuver Control Button (MANUV R/P)—
The maneuver control buttons are momentary
switches mounted on the right horn of the pilot’s
control wheel and on the left horn of the copi-
lot’s control wheel. Holding this switch de-
pressed momentarily disengages the roll and
pitch axes of the AFCS and allows the airplane
to be manually flown with the control wheel.
If a new attitude is established and the maneu-
ver switch is then released, the roll and pitch
axes of the AFCS automatically reengage, main-
taining the new pitch attitude (within limits) and
levels the wings. If maneuver limits are ex-
ceeded and the switch is released, the autopi-
lot will return the airplane to an attitude within
the maneuver limits, wings level, and 15° pitch.
Previously engaged roll and pitch axes modes
will be disengaged (HDG, ALT, and NAV, G/S,
REV CRS,
1
/
2
° Bank, SPD). If flying faster than
0.78 M
I
(0.79 M
I
on 24 series airplanes), the au-
topilot warning horn will sound with the
MANUV R/P switch engaged.
Pitch Sync Switch (not installed on Model
23)—When the pitch sync switch between the
thrust levers (labeled “A/P PITCH REL” on
airplanes with go-around [GA] switch) is de-
pressed, autopilot pitch axis will disengage
and pitch attitude changes may be made by
moving the control column or trimming. When
the pitch sync switch is released, the autopilot
will maintain airplane pitch attitude (within
limits) existing when the switch is released.
Depressing the pitch sync switch will disengage
SPD, ALT, or G/S ARM modes if previously se-
lected. The overspeed warning horn will sound
if the pitch sync switch is depressed at speeds
above 0.78 M
I
(0.79 M
I
24 series).
16-6
FOR TRAINING PURPOSES ONLY
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
WHEEL
MASTER
SWITCH
FOUR-WAY
TRIM
SWITCH
MICROPHONE
SWITCH (NOT
SHOWN)
MANEUVER
CONTROL
SWITCH
FD 108/FD 109
PITCH SYNC
SWITCH
Figure 16-8. Control Wheel Switches (Pilot’s)
