Gulfstream G550, Operating Manual

Page: 72 / 94

with the yoke or autopilot while the speed brake handle is extended, the
two outboard spoiler panels on each wing will increase displacement over
the speed brake commanded spoiler position to aid in aileron roll control.
The maximum displacement of the outboard spoiler panels is fifty-five
degrees, plus or minus four degrees (55°
±
4°) with full speed brake and
aileron commands.
B. Ground Spoilers:
The automatic operation of all six spoiler panels to reduce landing roll
distance or decrease stopping distance in the event of an aborted takeoff is
an electrically controlled function. Ground spoilers use no manual inputs
via control cables or linkages but instead use electro-hydraulic servo
valves to control the flow of hydraulic system pressure within the ground
spoiler hydraulic actuators to extend the spoiler panels. The servo valves
are electrically operated and use left hydraulic system pressure to control
the actuators. If left system pressure is not available, Power Transfer Unit
(PTU) pressure or Auxiliary (AUX) system pressure will operate the servo
valves using left system fluid.
To provide protection against spurious activation of the ground spoilers,
two levels of servo control safeguards are incorporated. The servo valves
are plumbed in series and both must be open to command actuation of
ground spoilers, and each servo valve has an independent electrical power
circuit for operation.
When the servo valves operate the ground spoiler actuators, system
operation is the same as that in speed brake operation: the hydraulic
actuators use both left and right hydraulic system pressure, reduced to
fifteen hundred (1,500) psi. to operate the inboard spoiler panels and the
mechanical linkage to the outboard flight spoiler actuators commands
operation of the two outboard panels on each wing. All six wing panel
spoilers extend to fifty-five degrees plus or minus four degrees (55°
±
4°).
For automatic operation, ground spoilers must first be armed using the
GND SPLR pushbutton on the cockpit center console (the SPOILER
CONTROL switch must also be in the ON position). The ground spoiler
pushbutton has two positions, OFF or ARMED, and the corresponding
legend within the pushbutton will illuminate according to the selection
made. See Figure 22. With the pushbutton ARMED, the ground spoilers
will activate whenever all the required elements in the operational logic are
satisfied.
Normal Operational Logic:
Because the simultaneous deployment of all six spoiler panels to fifty-five
degrees (55°) results in such an abrupt change in the wing airfoil, the
logical steps necessary for activation are designed to ensure that
automatic operation occurs only on the ground and with the concurrence of
the flight crew. The following conditions must be met to automatically
deploy ground spoilers during normal landing operations:
(1) The SPOILER CONTROL pushbutton selected ON.
(2) The GND SPLR pushbutton selected to ARM.
(3) Wing flaps selected to greater than twenty-two degrees (22°).
(4) Both power levers retarded to flight idle.
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS
2A-27-00
Page 72
August 14/03
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