Hawker 800 XP, Pilot Training Manual

Page: 402 / 504

Stall Warning System
The stall warning system uses an electrically
driven stick shaker on each control column to
provide a physical warning of an approaching
stall to the pilots.
Angle-of-attack is derived from two airflow
angle sensor vanes (Figure 15-21) mounted
one on each side of the forward fuselage.
Electrical signals proportional to vane angle
are sensed in the associated SSU which also
receives inputs relating to flap angle. From the
flap angle signal, the SSU calculates the point
of stall warning. When the vane angle corre-
sponds to that point, the SSU provides an out-
put to operate the stick shaker motor on each
control column.
The stall warning system is inhibited while
the aircraft weight is on the wheels to prevent
wind gusts triggering false stick shaker op-
erations on the ground. At takeoff, the sys-
tem is armed and commences to monitor the
pitch attitude of the aircraft.
Stall Identification System
The stall identification system uses a hydraulic
stick pusher to force the control column for-
ward (pitch down) at the calculated point of
stall. The stick pusher is powered by main hy-
draulic system pressure (backed by the main
accumulator). The rate of operation is con-
trolled by a fluid restrictor. Control of the hy-
draulic pressure to the stick pusher is via two
independent stall valves (A and B), connected
in series and mounted integrally with the stick
pusher. Both stall valves must be open to ac-
tivate the unit.
15-22
FOR TRAINING PURPOSES ONLY
HAWKER 800 XP PILOT TRAINING MANUAL
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Figure 15-19. Stall Warning and Identification System Schematic
I
N
P
U
T
INDENT
WARN
VANE
ANGLE
SENSOR
VANE
ANGLE
SENSOR
FLAP
ANGLE
SSU
SSU
3
RD CHANNEL
STALL VENT
3
RD CHANNEL
STALL VENT
LEFT AND
RIGHT
STICK-
SHAKER
MOTORS
3
RD
CHANNEL
STALL
VALVE
A
STALL
VALVE
B
STICK PUSHER
HYDRAULIC
PRESSURE
I
N
P
U
T
WARN
INDENT