Mechanical Control Path
For spoilers 4 and 11, a cable system connects the control wheels to the spoiler PCUs. Cable movement supplies a mechanical input to the PCUs which move the spoilers. The movement of the PCU housing supplies mechanical position feedback.
Roll Control -Autopilot Operation
When engaged, the autopilot flight director computers (AFDCs) control the roll rate and attitude of the airplane. They supply roll commands to the PFCs through the flight controls ARINC 629 buses. The PFCs use these inputs to calculate position commands for the spoilers.
The PFCs also calculate wheel backdrive commands. The PFCs send these commands to the AFDCs, which calculate control wheel movement commands for the backdrive actuator. The backdrive actuator moves the control wheels the same amount as the pilot would move them manually for the same surface movement. This supplies the mechanical signal to move spoilers 4 and 11.
To override the autopilot, the flight crew applies more force on the control wheel than the backdrive actuator force.
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SPOILER AND SPEEDBRAKE CONTROL -GENERAL DESCRIPTION
Speedbrake Control
The speedbrake lever transducers change the speedbrake lever movements to analog electrical signals.
These signals go to the four ACEs. The ACEs change the signals to digital format and send them to the three PFCs through the flight controls ARINC 629 buses.
The PFCs use the speedbrake lever position along with data from the ADIRU and AIMS, to calculate speedbrake commands. The PFCs mix these speedbrake commands with the spoiler roll commands. The PFCs send the mixed digital commands to the ACEs, which change them to analog signals. Except for spoilers 4 and 11, the ACEs send the analog position commands to the spoiler PCUs. The position transducers on the actuator pistons supply position feedback to the ACEs.
For spoilers 4 and 11, speedbrake control is only available in normal mode. When the pilot moves the speedbrake lever more than 54 degrees, the PFC commands the ACE to send an ON/ OFF electrical signal to the two spoiler PCUs.
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SPOILER AND SPEEDBRAKE CONTROL -GENERAL DESCRIPTION
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SPOILER AND SPEEDBRAKE CONTROL -FLIGHT DECK COMPONENT LOCATIONS
General
Many spoiler and speedbrake control components are in the flight deck and below the flight deck floor.
Flight Deck Components
The control wheels and speedbrake lever are in the flight deck. The speedbrake lever is on the captain’s side of the control stand. The speedbrake lever transducer is in the control stand.
Components Below the Flight Deck
The spoiler forward controls are below the flight deck floor and above the nose gear wheel well. These include the wheel position transducers and the spoiler control quadrant.
Access to these components is by panels in the flight deck floor. Access is also through the main equipment center (MEC), and then forward along the nose gear wheel well.
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SPOILER AND SPEEDBRAKE CONTROL -FLIGHT DECK COMPONENT LOCATIONS
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SPOILER AND SPEEDBRAKE CONTROL -WING CENTER SECTION AND WING COMPONENT LOCATIONS
General
Several spoiler and speedbrake control components are in the wing center section and in the wings.
Wing Center Section Components
The control cables for spoilers 4 and 11 connect the forward quadrant to the spoiler control mechanism quadrants and to the spoiler PCU quadrants. The cables go below the flight deck and passenger compartment floor, along RBL 21, to the wing center section.
The spoiler control mechanism quadrants are in the wing center section of the airplane, above the slant pressure deck and below the passenger floor. The cables go from the control mechanism quadrants through the overwing floor beams, and out along the wing rear spar to the spoiler PCU quadrants.
To get access to the control mechanism quadrants, you remove the floor panels in the passenger compartment.
Wing Components
The spoiler control surfaces and their PCUs are on the wings. One PCU connects to each surface.
The spoiler PCU quadrants for spoilers 4 and 11 are next to the PCUs.
To get access to the PCUs and quadrants, there are access panels on the lower wing.
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