Learjet 60 - Stall Warning System; Warning Systems

Learjet 60

Pilot's Manual
WARNING SYSTEMS
STALL WARNING SYSTEM
A stall warning system is installed to provide the crew with visual
and
tactile warning of an impending stall . The major components of
the
stall warning system consist of the following : left and
right stall vanes
on the forward fuselage, a two-channel computer-amplifier, flap
posi-
tion switches for each flap, two 18,100-foot altitude
switches, a stick
shaker for each crew position, an angle-of-attack indicator for each
crew position, L and R STALL warning lights, and associated
aircraft
wiring .
The flap position switches provide bias information
to the
computer-amplifier which will decrease stall warning
speeds as the
flaps
go from 0° to 40° . Above approximately 18,100
feet pressure alti-
tude,
the altitude switches bias the system to increase
stall warning
speeds approximately
15 knots . The stick shakers are eccentric
weights
driven by an electric
motor and actuation is evidenced by
a high-
frequency
vibration of the control columns . The left
and right systems
are
completely independent and utilize separate
electronics, stall
vanes, altitude
switches, shaker motors, and
flap switches . The stall
warning system
operates on 28 VDC supplied
through the 5-amp L
and R STALL WARN
circuit breakers on the pilot's
and copilot's cir-
cuit breaker panels
respectively . The stick shaker
and STALL warning
light circuits
are wired through the squat
switches ; therefore, the
stick
shaker and
STALL warning lights are
deactivated when the
squat
switches are
in the ground mode .
The stick shaker and STALL
warn-
ing
lights will be deactivated for 3 to 5
seconds after lift-off .
The angle-
of-attack
indicators remain active
both on the ground
and inflight,
however the angle of attack
displays are not
available on the PFD
while on the ground . The
stall warning systems
may be tested on
the
ground using the rotary-type
systems test switch,
located on the
center
instrument panel .
During flight, the stall
warning vanes align
with the local
airstream
and transducers produce
a voltage proportional
to airplane angle
of at-
tack . The transducer
signals are transmitted
to the appropriate
com-
puter-amplifier
channel along with flap
position information
from the
flap position
switches and altitude
information from the
altitude
switches . The
angle-of-attack indicator pointers
will enter the
yellow
segment, the L and R
STALL lights will
illuminate and flash,
and the
stick shakers will
actuate when the angle
of attack increases
to an an-
gle
corresponding to an airspeed at least
7% above the stall
speed pub-
lished
in the Airplane Flight Manual
.
PM-123
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