Gulfstream G550, Operating Manual

Page: 61 / 94

2A-27-60: Stall Warning and Prevention System (SWPS)
1. FAA Certified Airplanes Versus JAA Certified Airplanes:
In some instances, the Stall Warning and Prevention System (SWPS) differs
between FAA certified airplanes and JAA certified airplanes. This section presents
a description of the system installed in FAA certified airplanes. A synopsis of the
differences for JAA certified airplanes is presented in the Limitations portion of
this description.
2. General Description:
The SWPS provides the flight crew with visual indications of deteriorating
airspeed and high angles of attack, a physical warning of an impending stall by
activation of a yoke stick shaker and automatic elevator flight control movement
by a stick pusher to decrease angle of attack.
The SWPS functions are hosted in the autopilot (AFCS) processor modules of
Modular Avionics Units (MAUs) #1 and #2. Since each MAU autopilot module is a
fully-redundant independent processor, the SWPS is also a redundant system,
with each MAU using separate data inputs from Angle of Attack (AOA) sensors,
Flap Control Unit (FCU) channels, Inertial Reference Systems (IRSs), Air Data
Systems (ADS) and Display Controllers (DCs). Each MAU also has independent
outputs through Actuator Input/Output Processors (AIOPs) to separate channels
for the yoke stick shakers and hydraulic actuator valves of the yoke stick pusher.
A schematic of the system is contained in Figure 17.
Operation of the SWPS is controlled by the STALL BARR switch on the cockpit
center console. The SWPS must be operative prior to commencing flight, and the
switch is required to be selected on for all flight operations unless a malfunction
occurs during flight. (See Figure 18.)
3. Description of Subsystems, Units and Components:
A. Angle of Attack (AOA) Sensors:
Because an aircraft stall is an aerodynamic condition caused by separation
of the boundary layer of airflow over the wing at high angles of attack, AOA
data is more accurate than airspeed in determining the onset of a stall.
Airspeed is closely related to AOA, but is subject to indication and
compressibility errors - however, since airspeed is the standard reference
used by flight crews to control angle of attack, the airspeed indication
displayed on the Primary Flight Display (PFD) provides the best cues to the
onset of a stall condition. Angle of attack is included on the PFD, but in an
abbreviated format.
Two AOA sensors are installed on the G550, one on each side of the
aircraft positioned below and aft of the pilot and copilot windows. The AOA
sensors are powered and heated by the respective side essential DC bus
(left AOA by left essential DC bus, etc.). The AOA sensors are vanes that
measure the relative wind generated by the aircraft flight path. Each AOA
vane is mounted on a shaft that allows the vane to rotate, aligning the vane
into the relative wind. The amount of vane rotation is measured internally
by the AOA sensor and transmitted over ARINC-429 connections to the
MAUs (the left AOA sensor to MAU #1, right AOA sensor to MAU #2). The
SWPS function of the AFCS modules in the MAUs compare the relative
wind data with effective chord of the aircraft wing to determine the aircraft
angle of attack.
The effective chord of the wing changes with flap extension and is sensed
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS
2A-27-00
Page 61
August 14/03
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