two-speed trim system), the stick pusher actu-
ates, then releases as the pointer recedes into the
yellow segment. Repeat the test, positioning the
switch to the L TEST position. The test switch is
disabled in flight by its respective squat switch.
OPERATION—AIRPLANES
WITH MKII WING
As angle of attack increases, vane-operated
transducers feed a voltage signal proportional to
airplane angle of attack to the computer/amplifi-
er. If angle of attack increases until speed is
approximately 7% above airplane stall speed, the
computer/amplifier causes the stick shakers to
energize and the L and R STALL lights to flash
(Figure 15-15).
When both vane-operated transducers simultane-
ously detect an angle of attack beyond stall con-
ditions, the computer/amplifier disengages the
autopilot and signals the pitch servo to apply
nosedown elevator (stick pusher). When angle of
attack decreases below the stall point, the stick
pusher releases.
Stick shaker actuation occurs when the pointer
of the indicator is in the yellow segment. The
stick pusher actuates when the pointer is in the
red segment, and, except for model 23 airplanes,
the STALL lights are on steady.
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
15-21
FOR TRAINING PURPOSES ONLY
PUSHER ACTUATION
SHAKER ACTUATION
NORMAL ACCELEROMETER
(1/2 g LIMITER)
ACCELEROMETER
CUTOUT BOX
BIAS
BOX
COMPUTER/
AMPLIFIER
VANE
VANE
STALL WARNING
L
R
AUTOPILOT
PITCH SERVO
SHAKER
MOTOR
SHAKER
MOTOR
L STALL
R STALL
*
*
FLAP POSITION INPUT
16
14
12
10
8
6
4
2
18
0
MK II
ANGLE
OF
ATTACK
16
14
12
10
8
6
4
2
18
0
MK II
ANGLE
OF
ATTACK
Figure 15-15. Stall Warning System—Airplanes with MKII Wing
