Learjet 20 Series Pilot Training Manual page 325

• Emergency pitch trim switch (up or
down)
• Pilot's VG erect button
• Pilot's DG slave/free switch (FREE po-
sition)
• Trim monitor test switch
• Roll monitor test switch
• Pitch trim selector switch in the OFF po-
sition
Turn Knob—The turn knob must be in detent
before the autopilot will engage. Once en-
gaged, it will command bank angles up to 30°,
but will disengage any horizontal modes
(HDG, NAV, REV CRS) that were engaged.
Pitch Command Wheel—When the pitch com-
mand wheel on the autopilot controller is rotated,
the autopilot will change airplane pitch attitude
in response to the pitch command rotation. Pitch
attitude change rate is approximately 1° per
second. Pitch command authority is limited to
10° nosedown and 20° noseup. Rotating the
pitch command wheel will disengage SPD, ALT,
or G/S ARM modes if they were previously
selected.
Navigation Mode—The navigation (NAV) mode
button is pressed to activate the autopilot func-
tion, which captures and tracks navigational
radio beams such as VOR and ILS. For NAV
mode functions, the No. 1 navigation receiver
must be tuned to the frequency of the selected
navigation aid, and the course pointer on the HSI
set to the desired course. Activation of the NAV
mode will cause the autopilot to intercept and
track the desired course.
REV CRS (Reverse Course Select)—For REV
CRS mode operation, the navigation receiver
must be tuned to a localizer frequency, and the
NAV mode must be engaged. When the REV
CRS button on the autopilot controller is de-
pressed, the localizer course information to the
autopilot is reversed, and the glide-slope signal
to the autopilot is locked out. REV CRS should
be used for back course localizer approaches
only. The REV CRS function is inoperative on
VOR frequencies, and disengaging the NAV
mode also disengages the REV CRS function.
When NAV and/or REV CRS buttons are de-
16-8
LEARJET 20 SERIES PILOT TRAINING MANUAL
FOR TRAINING PURPOSES ONLY
pressed, the HDG mode will disengage. Turning
the turn knob out of detent will disengage NAV
and/or REV CRS modes.
Heading Mode—The heading (HDG) mode
button is pressed to activate the heading select
function of the autopilot. This mode com-
mands the autopilot to turn the airplane as
necessary and fly a heading selected by the po-
sition of the heading bug on the HSI. Maximum
bank angle available using this mode is 28°.
This button will cancel NAV and REV CRS
modes if engaged. Turning the turn command
knob out of detent will disengage heading
(HDG) select mode.
Altitude Hold Mode—The altitude hold (ALT)
mode is selected to maintain the existing baro-
metric altitude. Using the pitch command
wheel will disengage altitude hold.
G/S ARM (Glide-slope Select)—When the G/S
ARM button on the autopilot controller is de-
pressed, the autopilot will capture and track the
ILS glide-slope signal. For G/S ARM to func-
tion, the navigation receiver must be tuned to a
localizer frequency, an active glide-slope signal
must be present, and REV CRS mode must not
be engaged.
a. If ALT mode is not engaged, and the
G/S ARM button is depressed, the glide-
slope function will engage if any glide-
slope signal is present.
b. If ALT mode is engaged and the G/S ARM
button is depressed, the glide-slope func-
tion will not engage until the glide-slope
pointer on the horizontal situation indi-
cator (HSI) is in the neutral (glide-slope
centered) position. When the glide-slope
center is intercepted and the glide-slope
function engages, the previously selected
ALT mode will disengage.
1/2 Bank Mode—1/2 bank mode is applicable
to airplanes SNs 25-270, 25-272, and subse-
quent. The push–on/push–off 1/2 BANK but-
ton on the autopilot controller is used in
conjunction with the HDG mode to limit bank
angles to half their normal value. The 1/2 bank
mode has no effect on the turn command or
NAV mode.
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