Wing Anti-Ice
The wing anti-ice part of the maintenance page shows this information:
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WING MANIFOLD PRESS -Pneumatic duct pressure in psig

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VALVE -WAI valve open, closed, or regulating

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AIR PRESS -Pressure downstream of the WAI valves in psig

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AIR FLOW -Air flow through the WAI valves in kg/min.

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ICE AND RAIN PROTECTION -ICE PROTECTION MAINTENANCE PAGE

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777 AIRCRAFT MAINTENANCE MANUAL

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WING ANTI-ICE -INTRODUCTION

Purpose
The wing anti-ice system heats some of the leading edge slats so that ice does not collect on them in flight.
General Description
The pneumatic system supplies bleed air to heat the leading edge slats. Slats 3, 4, and 5 on the left wing and slats 10, 11, and 12 on the right wing are heated. Two wing anti-ice (WAI) valves control the air flow from the pneumatic system to WAI ducts. The WAI ducts carry the air to the slats. Holes in the bottom of each slat let the air out.
The airfoil and cowl ice protection system (ACIPS) control card -WAI controls the wing anti-ice valves. WAI pressure sensors send WAI duct air pressure data to the control card.
The wing anti-ice selector in the flight deck lets the crew set automatic or manual control. With AUTO selected, the WAI system comes on when the ice detection system finds ice. The OFF and ON positions are for manual control.
See the ice detection system section for more information (SECTION 30-81).
BITE circuits in the control card monitor the condition of the system. The AIMS gives information about the system through the EICAS display, status display, and maintenance pages. You use the MAT to do ground tests of the system.
Except for ground tests, the WAI system only operates in flight. Air/ground information from the weight on wheels (WOW) cards or airspeed data from the air data inertial reference unit (ADIRU) tells the control card when the airplane is in flight.
The wing anti-ice system has these other interfaces:
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ASCPC (air supply cabin pressure controller)

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ECSMC (ECS miscellaneous card)

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WES (warning electronic system).

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777 AIRCRAFT MAINTENANCE MANUAL

WING ANTI-ICE -INTRODUCTION

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WING ANTI-ICE -WING COMPONENT LOCATIONS

Component Locations
These components are in the wing leading edge next to the outboard side of the engine strut:
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WAI valve

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WAI pressure sensor

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WAI ducts.

There are also WAI ducts in the leading edge slats.
All of these components are LRUs.
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WING ANTI-ICE -WING COMPONENT LOCATIONS

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WING ANTI-ICE -FLIGHT DECK AND MEC COMPONENT LOCATIONS

Component Locations
The anti-ice control panel is on the P5 overhead panel. The WAI airfoil and cowl ice protection system control card (WAI ACIPS control card) is in the P84 right systems card file.
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WING ANTI-ICE -FLIGHT DECK AND MEC COMPONENT LOCATIONS

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WING ANTI-ICE -WAI VALVE

Purpose
The WAI valve controls the flow of bleed air from the pneumatic system to the wing anti-ice ducts.
Physical Description
The WAI valve has these parts:
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Body

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Pneumatic actuator

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Torque motor

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Electrical connector

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Locking crank and position indicator

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Locking screw.

The valve is electrically controlled and pneumatically actuated.
Location
The WAI valve is in the WAI duct in the leading edge of the wing. The WAI valve access door is on the bottom of the wing leading edge, outboard of the engine strut.
Functional Description
The WAI ACIPS control card controls the current through the torque motor. The torque motor controls operation of the valve. With no electrical power to the torque motor, air pressure on one side of the actuator holds the valve closed. Electrical current through the torque motor allows air pressure to open the valve. As the torque motor current increases, the valve opening increases.
　
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