An electrical connector and two hydraulic tubes attach at the forward, left end of the PCU.
Physical Description
The inboard spoiler PCUs weighs about 25.2 lb (11 kg) each. The outboard spoiler PCUs weigh about 14.5 lb (6.4 kg) each. The electrically-controlled inboard and outboard spoilers PCUs are functionally identical.
The spoiler PCUs contains a hydraulic actuator with a control module. The inboard PCUs have a balanced actuator. The outboard PCUs have an unbalanced actuator. The control module contains:
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An electrohydraulic servo valve (EHSV)
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An extension check and relief valve with manual bypass
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An inlet filter.
The actuator piston has an LVDT that sends position feedback signals to the ACE.
Training Information Point
Use the manual bypass to extend the PCU for maintenance.
Install a spoiler PCU lock when the panel is in the up position.
Use the spoiler PCU rod end adjustment to rig the PCU.
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The rod end of the actuator has a grease fitting.
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General
The inboard and outboard spoiler PCUs, except for spoilers 4 and 11, have only one mode of operation.
Normal Operation
When the ACE energizes the EHSV to the extend or retract position, hydraulic system pressure moves the actuator. During a retraction command, the extension check valve stays closed and permits retract pressure to the actuator. During an extension command, the extension check valve opens and permits flow to return. The actuator LVDT supplies a position feedback signal to the ACEs. The ACEs use this signal to adjust the extend command current.
A spring forces the EHSV to the fully retracted position when there is no electrical signal. This permits hydraulic pressure through the closed extension check valve to keep the actuator retracted.
Operation Without Hydraulic Pressure
Without hydraulic pressure to the PCU, the closed extension check valve prevents extension of the PCU.
If the spoiler panel is up at the time of hydraulic power loss, the airload on the spoiler causes hydraulic fluid to flow through the extension check valve and the EHSV. This permits the actuator to retract.
The thermal relief valve cracks open at about 3700 psid and closes at about 3100 psid.
Manual Operation
You can open the extension check valve with the manual bypass. With the extension check valve open, you can raise the spoiler without hydraulic power. You can lower the spoiler panel with the extension check valve closed.
Indications
The advisory message SPOILERS shows when one or more pair of spoilers is shut down.
The status message FLIGHT CONTROL SYS shows when one or more spoiler actuator fails.
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SPOILER AND SPEEDBRAKE CONTROL -SPOILER SURFACES
Purpose
The spoilers supply roll control in flight and speedbrake control during descent and landing.
Physical Description
The four inboard and ten outboard spoilers are light-weight composite materials structures. The skin is reinforced graphite/ epoxy bonded to a core of Nomex honeycomb.
The inboard spoilers weigh about 47 lb (21 kg) each. The outboard spoilers weigh about 30 lb (14 kg) each.
The overall dimensions of the inboard spoiler are approximately 42 in by 80 in (1.1 m x 2.0 m). Each spoiler attaches to the outboard rear spar with two outer hinge fittings, and one center hinge. The PCU actuator rod end connects to the actuator fitting.
The overall dimensions of the outboard spoiler are approximately 28 in by 78 in (0.7 m x 2.0 m). Each spoiler attaches to the spoiler beam with two outer hinge fittings, and one center hinge. The PCU actuator rod end connects to the actuator fitting.
Rubber bulb aeroseals attach to the inboard and outboard edges of all spoiler panels.
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