motor operation (but prior to pusher operation), a
push command is applied to the pitch servo with
approximately 1/4 the force of the pusher.
OPERATION—AIRPLANES
WITH STANDARD WING
The vane-operated transducer provides a voltage,
proportional to airplane angle of attack, to the
computer/amplifier. If angle of attack increases
until airspeed is 7% above stick pusher actuation
speed, one or both stick shakers are energized and
one or both red STALL lights begin to flash
(Figure 15-13). When both vanes simultaneously
increase to 5% above aerodynamic stall condition,
the computer/amplifier signals the autopilot to dis-
engage and the pitch servo to apply nosedown ele-
vator (stick pusher). When angle of attack decreas-
es below the stall point, the pusher releases.
Stick shaker actuation occurs as the pointer
sweeps 1/3 to 1/2 into the yellow segment of the
indicator. The stick pusher actuates as the indica-
tor moves into the red segment.
LEARJET 20 SERIES PILOT TRAINING MANUAL
FlightSafety
international
15-19
FOR TRAINING PURPOSES ONLY
Figure 15-13. Stall Warning System—Airplanes with Standard Wing
ANGLE-OF-ATTACK
INDICATOR
PUSHER ACTUATION
SHAKER ACTUATION
NORMAL ACCELEROMETER
(1/2 g LIMITER)
ACCELEROMETER
CUTOUT BOX
BIAS
BOX
COMPUTER/
AMPLIFIER
TO LH
ANGLE-OF-ATTACK
INDICATOR
VANE
VANE
STALL WARNING
L
R
AUTOPILOT
PITCH SERVO
SHAKER
MOTOR
SHAKER
MOTOR
L STALL
R STALL
*
*
FLAP POSITION INPUT
