The multi-function spoilers help the ailerons with roll control, mixed with roll assist and proportional lift dumping (in flight speedbrake). They also help the ground spoilers with ground lift dumping (GLD) (on ground speedbrake).

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There is one PCU for each multi-function spoiler (MFS) control surface. Each PCU has an electro-hydraulic servo valve (EHSV), an extend check and thermal relief valve and a linear variable-differential transducer (LVDT).

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There are two MFS control surfaces installed on the top trailing edge of each wing. A power control unit (PCU) is attached to each MFS control surface. The PCU uses hydraulic pressure to extend and retract the MFS. The MFS control surfaces can be moved to any position from full up to full down.

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The spoiler electronic-control units (SECUs), in the LH equipment compartment, receive data signals from the four rotary variable differential transducers (RVDTs). The RVDTs are found in the flight-spoiler control lever (FSCL) in the flight compartment. The SECUs use this data to tell the ground-spoiler selector valves (GSSVs), in the left and right wheel-wells, when to operate the PCUs. The GSSVs give or cut off hydraulic pressure to the PCUs. The PCUs then move the MFS control surfaces.

The GSSVs are electrically controlled with the signals from the applicable SECU. Each GSSV contains three solenoids (an arm, a command and a MFS solenoid). During regular operations (with no electrical signals supplied to the MFS solenoid) the EHSV is set. This will apply hydraulic pressure to the retract side of the EHSV and hold the PCU in the full retract position.

When the MFSs are in the retract mode, the MFS solenoids do not have an electrical signal. This causes the pressurized hydraulic fluid to hold the PCU in the retract position. When the MFS control surfaces are set to the extend position, the SECU sends electrical signals to the GSSV. These electrical signals energize the MFS solenoid which then energizes the EHSV to a position that will apply hydraulic pressure to extend the PCUs. Hydraulic pressure is then sent through the extend check valve to the PCU actuators, which moves the MFS controls surfaces up.

The PCUs are attached to the MFS control surface with an eccentric bolt. The eccentric bolt is turned to adjust the tension load of the MFS control surface (with the MFS control surface in the retract position). The PCU is attached to the wing with a pivot pin. This lets the PCU turn on the pivot axis while the MFS moves.

When the multi-function spoilers operate, hydraulic pressure from the GSSV is moved to the EHSV. The extend check and thermal relief valve will let the EHSV move fluid.

Hydraulic pressure is supplied to the extend chamber of the actuator and the retract chamber opens to the return. The SECU sends a spoiler extend signal to the PCU. The EHSV pressure then extends the actuator.

The extend check and thermal relief valve (in the EHSV) prevents fluid flow out of the retract chamber of the actuator, when there is no hydraulic pressure. This does not let the actuator move (float up) in the extend direction. But, the valve does let the actuator be blown down in the retract direction. The extend check and thermal relief valve has a function to release hydraulic pressure. This gives the PCU protection from too much hydraulic pressure in the retract chamber from aerodynamic loads. This will not let the hydraulic pressure in the PCU retract chamber to be more than 4 500 psi.

The SECU sends a spoiler retract signal to the PCU. When this occurs, the GSSV sends fluid through the extend check and thermal relief valve, to the retract side of the actuator. Hydraulic pressure then moves to the retract side of the actuator and holds it in the retracted position. When the PTUs extend or retract, the LVDT supplies an electrical feedback signal to the SECU, in proportion to the PCU position.

The ROLL SPOILERS push-button-annunciator (PBA) is found on the GND/ROLL SPOILERS control-panel. If the aileron control circuit is not locked but the pilot's control wheel is locked, the pilot must then push the ROLL SPOILERS PBA. This will give control of the ailerons to the copilot and stop the roll aid function of the multi-function spoilers. When the PBA is pushed, the ROLL SPOILERS OFF light comes on. If the pilots wheel becomes unlocked and the PBA is pushed again, the ROLL SPOILERS OFF light goes off. Also, the roll aid function of the multi-function spoilers will start again.

The SECUs supply MFS position indication to the FLIGHT CONTROLS synoptic page of the multifunction display and to the EICAS display. This display shows the MFS movements in the up or down positions on a scale with arrows. The arrows show the MFS position in degrees from 0 degrees (stowed) to 45 degrees (fully deployed). The MFS arrows show red when the CONFIG SPOILERS warning message comes on. The arrows show amber when there is a unserviceable condition with the spoiler or the FLT SPOILERS DEPLOY caution message comes on. When there is no unserviceable spoiler condition or no messages shown then 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 FLT SPOILERS DEPLOY caution message will show when the flight spoilers are deployed below 500ft (not on ground) and/or the throttles are above idle (not on ground).

The FLT SPOILERS FAIL caution message will show when the flight spoilers have failed.

The FLT SPOILERS FAULT caution message will show when the inboard or outboard flight spoilers have failed.

The ROLL SPOILERS FAIL caution message will show when the roll assist function has failed.

The ROLL SPOILERS FAULT caution message will show when the inboard or outboard roll spoilers have failed.

The ROLL SPOILERS OFF caution message will show when the roll spoiler switch is set to OFF and the roll disconnect switch is not set to disconnect.

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 ROLL SPOILERS OFF status message will show when the roll spoiler switch is set to OFF and the roll disconnect switch is set to disconnect.

The EICAS messages that follow are related to the multi-function spoiler system:

EICAS MESSAGE(S)	LEVEL (COLOR)
CONFIG SPOILERS	WARNING (red)
FLT SPOILERS DEPLOY	CAUTION (amber)
FLT SPOILERS FAIL	CAUTION (amber)
FLT SPOILERS FAULT	CAUTION (amber)
ROLL SPOILERS FAIL	CAUTION (amber)
ROLL SPOILERS FAULT	CAUTION (amber)
ROLL SPOILERS OFF	CAUTION (amber)
SPOILERS FAIL	CAUTION (amber)
SPOILERS FAULT	CAUTION (amber)
SPOILERS FAULT	ADVISORY (cyan)
ROLL SPOILERS OFF	STATUS (white)

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The multi-function spoilers have an interface with the components that follow:

• Flight Spoiler Control Lever
• Ground Spoiler Selector Valve
• GND/ROLL SPOILERS Control Panel

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
MPE37	MULTI-FUNCTION SPOILER POWER-CONTROL UNIT (MFS PCU) (LH)	ZONE(S) 563	27−62−01
MPE39	MULTI-FUNCTION SPOILER POWER-CONTROL UNIT (MFS PCU) (LH)	ZONE(S) 564	27−62−01
MPE36	MULTI-FUNCTION SPOILER POWER-CONTROL UNIT (MFS PCU) (RH)	ZONE(S) 663	27−62−01
MPE38	MULTI-FUNCTION SPOILER POWER-CONTROL UNIT (MFS PCU) (RH)	ZONE(S) 664	27−62−01
-	MULTI-FUNCTION SPOILER CONTROL-SURFACE (LH)	ZONE(S) 563	27−62−05
-	MULTI-FUNCTION SPOILER CONTROL-SURFACE (LH)	ZONE(S) 564	27−62−05
-	MULTI-FUNCTION SPOILER CONTROL-SURFACE (RH)	ZONE(S) 663	27−62−05
-	MULTI-FUNCTION SPOILER CONTROL-SURFACE (RH)	ZONE(S) 664	27−62−05

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