Hawker Beechcraft Hawker 800XP, Руководство по эксплуатации для пилотов

Страница: 179 / 923

Page 7-4
Pilot’s Operating Manual
Revision A2: Nov, 2004
Sub-section 7
STALL WARNING/IDENTIFICATION
Hawker 800XP Pro Line 21
Section III - SYSTEMS DESCRIPTION
OPERATION
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 electrically heated airflow angle sensor vanes mounted one on each
side of the forward fuselage. Electrical signals proportional to vane angle are sensed in the associated
Signal Sensor Unit 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 corresponds to that point the SSU provides
an output to operate the stick shaker motor on each control column.
The stall warning system is inhibited while the airplane is on the ground with weight-on-wheels to
prevent wind gusts triggering false stick shaker operations. At takeoff, the system is armed and begins
monitoring the pitch attitude of the airplane.
STALL IDENTIFICATION SYSTEM
The stall identification system uses a hydraulic stick pusher to force the control column forward (pitch
down) at the calculated point of stall. The stick pusher is powered by main hydraulic system pressure
(backed by the main accumulator), the rate of operation being controlled by a fluid restrictor.
Control of the hydraulic pressure to the stick pusher is via two independent stall valves (A and B),
connected in series and mounted integral with the stick pusher. Both stall valves must be open to
activate the unit.
The output from one SSU energizes one stall valve, and an associated red STALL VLV (A or B) OPEN
annunciator is illuminated to indicate that the valve is being signalled to open (reference Figure 1).
The SSU uses the vane sensor and flap angle inputs to calculate the point of stall. The rate of increase
of vane angle may also modify the calculation, i.e. the point of stall being advanced when the rate of
increase is high dynamic stall (reference Figure 2).
When the vane angle agrees with the calculated point of stall, the SSU produces an output
(stall identification) to energize the associated stall valve and annunciator.
When a SSU produces a stall warning output, which is then followed by an identification signal, the
warning signal latches the stall identification relay for the same channel (reference Figure 3). A warning
signal from either channel will disconnect the autopilot and operate the stick shaker. The latch is
removed when the warning output ceases. This makes sure the stick push is maintained until the
airplane has reached a nose-down attitude well below the stall point.
M6950_0
HA00C
017045AA.AI
STALL
VLV A
OPEN
STALL
VLV B
OPEN
Figure 1
Stall Valve Annunciators