The ground spoilers remove lift from the wings when the aircraft is on the ground (speedbrakes). The ground spoilers has an interface with the components that follow:

• Wheel Speed Transducer
• Main Landing Gear (MLG) Proximity Sensor
• Nose Landing Gear (NLG) Proximity Sensor
• Radio Altimeter Transceiver
• Throttle Quadrant

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There are two ground-spoiler selector valves (GSSVs). One is found in the left wheel well and the other in the right wheel well. Each GSSV has hydraulic connectors that connect to the applicable ground spoiler actuator (GSA). An electrical connector connects the GSSV to the SECU. Each GSSV has an arming, a command and a multi-function spoiler solenoid.

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There is one GSA attached to each ground-spoiler control surface. The GSAs are simple two-position (fully extended or fully retracted) hydraulic actuators.

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There are two ground-spoiler control surfaces on each wing. A GSA, attached to each ground-spoiler control surface, uses hydraulic pressure to extend and retract the ground-spoiler control surface. Ground-spoiler control surfaces can only move to the full up or the full down position.

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The GND/ROLL SPOILERS control-panel is found on the center pedestal. The ROLL SPOILERS push button annunciator (PBA) is located on the right side of the panel and controls the multi-function spoilers. The GND SPOILERS switch is a three position switch (OFF, AUTO and MANUAL ARM) found on the left side of the panel.

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The spoiler electronic-control units (SECUs) are found in the LH equipment compartment. They receive data signals from the wheel speed transducer and the weight on wheels (WOW) proximity sensors. The SECUs also receive data from the radio altimeter transceiver and the throttle lever rotary variable differential transducers (RVDTs). The SECUs use this data to tell the ground-spoiler selector valves (GSSVs), in the left and right wheel wells, when to operate the GSAs. The GSAs then move the ground-spoiler control surfaces.

The ground-spoiler selector valves are electrically controlled with signals from the applicable SECU. Each GSSV contains three solenoids. If there is no electrical signal to the solenoids, the GSSVs will cause the ground-spoiler control surfaces to be in the full retract position.

When the ground spoilers are in the retract mode, the solenoids do not have an electrical signal. This causes the pressurized hydraulic fluid to hold the actuator in the retract position. When the ground-spoiler control surfaces are set to the extend position, the SECU sends electrical signals to the GSSV. These electrical signals energize the arming solenoid and the command solenoid to move the arming valves and the command valves hydraulically. The arming valves and the command valves move to a position that will apply hydraulic pressure to extend the GSAs. Hydraulic pressure is then sent through the extend tubes to the GSAs, which moves the ground-spoiler control surfaces to the full up position.

The GSAs are attached to the ground-spoiler control surfaces with an eccentric bolt. This eccentric bolt is used to adjust the ground-spoiler control surface. Turn the eccentric bolt to adjust the tension load of the GSA (with the GSA in the retract position). The GSA is attached to the wing with a pivot pin, this lets the GSA turn on the pivot axis as the ground-spoiler control surface moves.

During regular operations (with no electrical signals supplied to the arming solenoids and the command solenoids) the arming valves and the command valves are set. The arming valves and the command valves are set to apply hydraulic pressure to the retract side of the GSA (and hold the GSA in the retract position).

When ground spoilers operate, hydraulic pressure from the GSSV is moved to the GSA. Hydraulic pressure is supplied to the extend piston chamber and the retract piston chamber opens to the return.

The extend check and thermal relief valve (in the GSSV) prevents movement of the ground-spoiler control surfaces in the extend direction, when there is no hydraulic pressure. If there is movement to the retract position, the extend check and thermal relief valve will let the ground-spoiler control surfaces retract. The extend check valve and thermal relief valve have a function to release hydraulic pressure. This gives the GSA protection from too much hydraulic pressure in the retract piston chamber. This will not let the hydraulic pressure in the GSA be more than 4,500 psi.

The ground-spoiler control surfaces are installed on the top trailing edge of the wings. A GSA hydraulically operates each ground-spoiler control surface. The GSA receives its hydraulic input from its applicable ground-spoiler selector valve.

When the switch, on the GND/ROLL SPOILERS control-panel, is the in the OFF position it disables the ground spoiler function. In the AUTO position the switch automatically arms the ground spoiler function for landing and rejected take-off in conjunction with the throttle lever angle and wheel speed inputs. When the switch is in the MANUAL ARM position it arms the ground spoiler function regardless of the throttle lever angle and wheel speed inputs.

The SECUs supply ground spoiler position indication to the FLIGHT CONTROLS synoptic page multifunction display and to the EICAS display. This display shows the ground spoiler movements in the up or down positions on a scale with arrows. The arrows show the ground spoiler position at 0 degree (stowed) or 60 degrees (fully deployed). The ground spoiler arrows show red when the CONFIG SPOILERS warning message comes on. The arrows show amber when the ground spoiler is deployed before touchdown or it is deployed and unserviceable. When there is no spoiler deployed before the touchdown, or no deployed unserviceable spoiler, the arrows show green.

The CONFIG SPOILERS warning message will show when the aircraft is on ground and the spoilers are not correctly configured for take-off.

The GND SPLRS NOT ARMED caution message will show when the ground spoilers are not armed and not set OFF.

The GND SPOILERS FAIL caution message will show when the ground spoilers have failed. The SPOILERS FAIL caution message will show when the spoilers have failed.

The SPOILERS FAULT caution message will show when one or more of the spoiler PCU panels have failed, or one or more of the ground spoilers is up prior to touchdown.

The SPOILERS FAULT advisory message will show when a fault that causes the loss of redundancy has occurred in the spoiler system but does not affect spoiler operation.

The GND SPOILERS OFF status message will show when the ground spoilers are set OFF.

The EICAS messages that follow are related to the ground spoiler system:

EICAS MESSAGE(S)	LEVEL (COLOR)
CONFIG SPOILERS	WARNING (red)
GND SPLRS NOT ARMED	CAUTION (amber)
GND SPOILERS FAIL	CAUTION (amber)
SPOILERS FAIL	CAUTION (amber)
SPOILERS FAULT	CAUTION (amber)
SPOILERS FAULT	ADVISORY (cyan)
GND SPOILERS OFF	STATUS (white)

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
MPE34	GROUND-SPOILER SELECTOR VALVE NO. 1 (LH)	ZONE(S) 161	27−63−01
MPE35	GROUND-SPOILER SELECTOR VALVE NO. 2 (RH)	ZONE(S) 162	27−63−01
-	GROUND SPOILER ACTUATOR (LH)	ZONE(S) 561	27−63−05
-	GROUND SPOILER ACTUATOR (LH)	ZONE(S) 562	27−63−05
-	GROUND SPOILER ACTUATOR (RH)	ZONE(S) 661	27−63−05
-	GROUND SPOILER ACTUATOR (RH)	ZONE(S) 662	27−63−05
-	GROUND-SPOILER CONTROL SURFACE (LH)	ZONE(S) 561	27−63−09
-	GROUND-SPOILER CONTROL SURFACE (LH)	ZONE(S) 562	27−63−09
-	GROUND-SPOILER CONTROL SURFACE (RH)	ZONE(S) 661	27−63−09
-	GROUND-SPOILER CONTROL SURFACE (RH)	ZONE(S) 662	27−63−09
-	GND/ROLL SPOILERS CONTROL-PANEL	ZONE(S) 211	27−63−11

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