Gulfstream G550 Operating Manual Download

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breaker for the faulty stick shaker can be pulled (SHAKER #1 on the pilot
overhead panel, SHAKER #2 on the copilot overhead panel).

The MAUs monitor their respective data input paths and SWPS activation
paths for operational capabilities. If faults or failures are found, the status is
reported to the Monitor and Warning System (MWS) that will in turn
generate appropriate CAS messages for flight crew notification.

D. Yoke Stick Pusher:

If the visual display of low airspeed and high AOA in conjunction with
activation of the cockpit yoke stick shakers does not prompt a decrease in
AOA and airspeed gain, the SWPS function of the autopilot processors will
command the aircraft elevators to a nose down position in an attempt to
avoid stalling the aircraft wing. If the aircraft approaches a normalized AOA
of 1.00, each SWPS channel will separately signal activation of a dedicated
hydraulic solenoid valve on the stick pusher mechanism in the tail
compartment. The stick pusher mechanism is installed just aft of the dual
elevator hydraulic actuators, and employs a linkage connected by a cam
arm to provide a nose down movement to the input side of the elevator
actuators. Activation of the stick pusher will not interrupt the action of the
stick shakers.

The SWPS software provides an anticipatory function for the stick pusher,
so that at lower airspeeds, stick pusher activation will respond to the rate of
change in aircraft body angle (as sensed by the IRS) to prevent the aircraft
from overshooting the 1.00 AOA stall point. As airspeed increases from .76
Mach to .80 Mach the anticipatory function is biased out of the activation
logic, since large control inputs are not necessary at high airspeeds.

The stick pusher will deactivate the nose down input to the elevators when
aircraft acceleration drops below 0.5 G or the actual wing AOA decreases
3.6° below the stick pusher activation threshold.

If a malfunction causes a spurious activation of the stick pusher, a manual
force on the control column of approximately seventy-five pounds (75 lbs)
will overcome the nose down control input. The stick pusher may be
electrically disconnected by depressing either of the pilot or copilot yoke
A/P DISC BARR DISC switches or by selecting the STALL BARR switch on
the cockpit center pedestal to off (the OFF legend in the pushbutton switch
will illuminate amber). Normally the yoke switches are used if the crew is
hand flying the aircraft and the pedestal pushbutton is used during
autoflight to avoid disconnecting the autopilot.

The MAUs monitor the performance of the data inputs used to activate the
stick pusher and the health of the stick pusher hydraulic actuation
installation. Any degraded performance is annunciated to the crew through
MWS initiated CAS messages.

E. SWPS Ground Test:

Although the stall warning and prevention system does not operate with the
aircraft on the ground (weight on wheels), a preflight test of the system may
be conducted by selecting the system on the TEST menu of the Display
Controllers (DCs). Each independent SWPS channel has a dedicated Line
Select Key (LSK) on the DC TEST menu. Depressing the LSK next to the
STALL 1 or STALL 2 legend will first activate the stick shaker for one
second, then activate the stick pusher to the nose down position. The test

OPERATING MANUAL

PRODUCTION AIRCRAFT SYSTEMS

2A-27-00

Page 63

August 14/03

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