The wing anti-ice system does not let ice collect on the leading edge of the wings. It uses hot air from the high-pressure bleed-air of the engines, supplied through the anti-ice system, to give heat to the wings.

The wing anti-ice system is made up of high pressure ducts and piccolo ducts. The high pressure ducts transmit hot air from the high pressure port of the engines to the wing roots. High pressure ducts have a diameter of 2 in (5.08 cm) and connect the wing anti-ice valves (WAIV) to the piccolo ducts. The ducts also connect the left and right wing anti-ice systems. The two systems are isolated by the wing cross-bleed valve (CBV).

High pressure ducts have insulation which keep the surface temperature to a limit of 392 °F (200 °C). The shell of this insulation has small holes. Air leakage from the ducts is collected in the shell and released through these small holes. This points the hot air on the loops of the leak detection system. Ducts with insulation have flanges which are attached together by Inconel band clamps. The band clamps have covers made from silicon-rubber material.

The duct system is a tension and compression system which is made from stainless steel and titanium alloys. Flexible joints are installed along the ducts to give some tolerance to the duct installation, to give some freedom for structural movement and to let the ducts expand because of the heat. There is a flexible joint after the pylon on the structural side (left and right side). There are three flexible joints downstream of the WAIV (left and right sides). Before the wing root, there are three flexible joints (left and right sides).

The piccolo ducts transmit the hot air from the high pressure ducts along the total span of the wing leading edge. The ducts have small holes in their forward face which points the hot air to the inner surface of the wing leading edge. The piccolo ducts have two rows of staggered holes with a space of 30 degrees between them. The diameter of the piccolo ducts decreases from 2 in (5.08 cm) at the wing root to 0.75 in (1.91 cm) at the wing tip. The piccolo ducts are divided in five different diameters: 2 in (5.08 cm), 1.75 in (4.45 cm), 1.5 in (3.81 cm), 1.25 in (3.18 cm) and 0.75 in (1.91 cm). The piccolo ducts are connected by Inconel band clamps and slip joints.

The slip joints let the ducts expand because of the heat and give some freedom for structural movement. Air leakage from the ducts is sensed by the loops of the leak detection system.

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The wing anti-ice valve (WAIV) controls the flow of hot air from the engines to the wing leading edges. The WAIV is found in the aft equipment compartment, downstream of the high pressure valve. There are two WAIVs in the aircraft. One for the left wing anti-ice system and one for the right wing anti-ice system. The valve has the internal parts that follow: a butterfly plate, a pneumatic actuator, an opening spring, a diaphragm, a microswitch and a torque motor.

The valve body is a 2 in (5.08 cm) and is made of stainless steel. The valve body has an upstream pressure tapping to supply the pressure reducer. The WAIV is a pneumatically operated butterfly valve. There is a microswitch which sends a signal to the EICAS to show the OPEN or CLOSED position of the butterfly plate. The WAIV is controlled by the IAS controller.

The pneumatic actuator is supplied with pressure by an orifice, operated by the torque motor. The torque motor is controlled by a signal from the IAS controller as a function of the inboard leading-edge temperature. The valve can be overridden manually. This lets the valves be mechanically set and locked in the CLOSED position. A screw which is attached to the valve can be installed on the pneumatic actuator to lock the lever. This lever also gives a visual indication of the valve position.

The IAS controller supplies the current to the torque motor, which opens or closes the butterfly plate of the WAIV. The current applied is a function of the input that the IAS controller receives from the inboard leading-edge temperature sensor. Without upstream pressure, the valve is closed. With upstream pressure and no current applied to the torque motor, the valve is closed. With upstream pressure and the current applied to the torque motor (maximum of 250 mA), the valve is open and controls the air flow.

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There are two anti-ice s-ducts (one left and one right) found in the aft equipment compartment. They connect to the wing anti-ice valves and to the cross-under ducts.

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There are two cross-under ducts (one left and one right) found in the wing fairings. They connect to the anti-ice S-ducts and to the aft fuselage ducts. In the case of an engine or a bleed malfunction, the cross-under ducts connect the left and the right wing anti-ice systems through the wing cross-bleed valve.

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There are two aft fuselage ducts (one left and one right) found in the wing fairings, aft of the main landing-gear (MLG) wheel wells. The aft fuselage ducts connect to the cross-under ducts and to the wheel well ducts.

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There are two wheel well ducts (one left and one right) found in the MLG wheel wells. They connect to the aft fuselage ducts and to the overwing ducts.

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There are two overwing ducts (one left and one right) found in the over-wing fairings. They connect to the wheel well ducts and to the wing supply ducts.

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There are two wing supply ducts (one left and one right) found in the over-wing fairing, at the wing roots. They connect to the overwing ducts and to the inboard piccolo ducts.

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There are two inboard piccolo ducts (one left and one right) found in the wing leading edges, near the wing roots. They connect to the wing supply ducts and to the inboard slip joints.

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There are two middle piccolo ducts (one left and one right) found in the wing leading edges. They connect to the inboard slip joints and to the outboard slip joints.

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There are two outboard piccolo ducts (one left and one right) found in the wing leading edges, near the wing tips. They connect to the outboard slip joints only.

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There are two inboard slip joints (one left and one right) found in the wing leading edges. They connect to the inboard piccolo ducts and to the middle piccolo ducts.

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There are two outboard slip joints found in the wing leading edges. They connect to the middle piccolo ducts and to the outboard piccolo ducts.

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The wing anti-ice system uses hot air directly from the high-pressure bleed-air system. The temperature of the air supplied is not controlled. It changes with aircraft speed, altitude, ambient temperature, and engine speed. If one of the two engines has a malfunction, it may supply air at a higher temperature. The wing anti-ice system can operate to a maximum bleed air temperature of 932 °F (500 °C).

The left and right wing anti-ice systems operate independently of each other. This configuration makes sure that sufficient hot air is supplied to keep the leading edges free of ice. It also decreases the volume of air necessary from each engine. This gives a better control on each side of the aircraft which corrects for differences in valve properties and changes in heat load.

Usually, the system is off. It is not turned to ON automatically. If the ice detection system senses an ice condition, it will give an ICE DETECTED caution message on the EICAS display. The flight crew must then manually push the WING, L ENG, and R ENG pushbutton annunciators (PBAs) on the ANTI-ICE control panel. This causes the light in the PBAs to come on and turns on the wing and the nacelle anti-ice system. The IAS controller sends a signal to the stall protection computer to adjusts for an ice condition. At the same time, the ICE DETECTED caution message changes to an ICE DETECTED advisory message on the EICAS display.

With the wing anti-ice system set to ON, the WAIVs automatically control the flow of hot air that goes to the leading edge of the wings. The inboard leading-edge temperature-sensors, found near the wing root, supplies a signal to the IAS controllers. The IAS controllers then send a command signal to the solenoid of the WAIVs. The solenoid opens or closes the WAIVs as a function of the signal from the IAS controllers.

If the temperature in the leading edges is low, the outboard leading-edge temperature-sensors, found near the wing tip, supplies a signal (low temperature) to the IAS controllers. The IAS controllers then send a signal to the data concentrator unit (DCU) which uses it to show the L (R) WING ANTI-ICE FAIL caution message. This message shows while the wing anti-ice system is set to ON. Then, the flight crew usually sets the WING SOURCE rotary switch to FROM L or FROM R (as necessary).

The anti-ice system has a wing CBV which can connect the two sides, if one of the malfunctions that follow occurs:

• One engine has a malfunction
• A high pressure valve (HPV) has a malfunction
• A WAIV has a malfunction
• The bleed air supply has a malfunction on one side (upstream of the WAIV).

Usually, the WING SOURCE rotary switch on the ANTI-ICE control panel is set to NORM. If one of these malfunction occurs, the flight crew turns the WING SOURCE rotary switch to FROM L or FROM R.

In a cross flow operation (FROM L or FROM R), the two wing anti-ice systems be supplied with hot air from only one source (the left or right engine). The IAS controller No. 1 or No. 2 sends the open command to the wing CBV. This manually sets the wing CBV to the fully opened position and sets the related WAIV and HPV to the fully closed position.

When the WING SOURCE rotary switch is set to FROM L, the bleed source is supplied from the left engine (the wing CBV is fully opened, the right HPV and WAIV are fully closed). When the WING SOURCE rotary switch is set to the FROM R position, the bleed source is supplied from the right engine (the wing CBV is fully opened, the left HPV and WAIV are fully closed).

The IAS controllers monitor and control the wing anti-ice system. They send EICAS messages to the DCU to be shown on the EICAS display. System status is also shown to the flight crew on the EICAS anti-ice synoptic page.

The WING ANTI-ICE LEAK warning message will show when a hot air leak condition in the wing anti-ice ducts downstream the HPV is sensed by the IAS controllers.

The L (R) WING A/I LOW TEMP caution message will show when the left (right) leading-edge-outboard low temperature is sensed.

The L (R) WING A/I PRESS HIGH caution message will show when an over-pressure condition is sensed downstream of the left (right) HPV.

The L (R) WING ANTI-ICE FAIL caution message will show when there is one of the conditions that follow:

• The left (right) leading-edge-outboard low temperature is sensed
• The left (right) WAIV is set ON and the left (right) WAIV has a malfunction in the closed position
• The left (right) WAIV is set ON and the two left (right) inboard temperature-sensor-channels have a malfunction
• The left (right) WAIV is set ON and there is a difference in temperature between the two left (right) inboard temperature-sensor-channels
• The left (right) WAIV is set ON and the left (right) torque-motor driver has a malfunction
• The IAS controller No.1 (2) has a malfunction
• A leak was found in one of the wing anti-ice ducts and was stopped after the WAIV automatic shutdown.

The WING ANTI-ICE FAULT caution message will show when the two left and right outboard leading edge temperature-sensor-channels have a malfunction.

The WING ANTI-ICE FAULT advisory message will show when:

• An inboard leading-edge temperature sensor is out of range
• An outboard leading-edge temperature sensor is out of range
• The wing CBV has a malfunction in the open or closed position
• The left (right) WAIV is not set ON and there is a difference in temperature between the two left (right) inboard temperature-sensor-channels
• The left (right) WAIV is not set ON and there is a difference in temperature between the two left (right) outboard temperature-sensor-channels
• A pressure sensor is out of range.

The WING ANTI-ICE ON status message will show when the WING PBA, on the ANTI-ICE control panel, is pushed and the light comes on.

The WING/ENG ANTI-ICE ON status message will show when the WING, L ENG, and R ENG PBA, on the ANTI-ICE control panel, are all pushed and their lights come on.

The EICAS messages that follow are related to the wing anti-ice system:

EICAS MESSAGE(S)	LEVEL (COLOR)
WING ANTI-ICE LEAK	WARNING (red)
L WING A/I PRESS HIGH	CAUTION (amber)
R WING A/I PRESS HIGH	CAUTION (amber)
L WING ANTI-ICE FAIL	CAUTION (amber)
R WING ANTI-ICE FAIL	CAUTION (amber)
WING ANTI-ICE FAULT	CAUTION (amber)
WING ANTI-ICE ON	STATUS (white)
WING/ENG ANTI-ICE ON	STATUS (white)
L WING A/I LOW TEMP	CAUTION (amber)
R WING A/I LOW TEMP	CAUTION (amber)

WING TEMPERATURE SENSOR – WING OVERHEAT

WING TEMPERATURE SENSOR – WING ANTI-ICE FAIL

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The status of the WAIVs is shown on the ANTI-ICE synoptic page. The WAIVs are shown with a fixed contour and a flow line that moves (valve opened/valve closed). The contour color is white and the flow line color is usually the same as the one of the adjacent flow lines. The ducts are shown as flow lines. The flow lines color can be one of those that follow:

• Red to show an unserviceable status
• Amber to show a caution
• White to show a usual status with no airflow
• Green to show a usual status with airflow
• Magenta to show invalid or unknown status

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
MPE13	WING ANTI-ICE VALVE (LH)	ZONE(S) 311	30-12-01
MPE12	WING ANTI-ICE VALVE (RH)	ZONE(S) 312	30-12-01
-	ANTI-ICE S-DUCT	ZONE(S) 311 ZONE(S) 312	30-12-07
-	CROSS-UNDER DUCT	ZONE(S) 182	30-12-09
-	AFT FUSELAGE DUCT	ZONE(S) 182	30-12-11
-	WHEELWELL DUCT	ZONE(S) 171 ZONE(S) 172	30-12-13
-	OVERWING DUCT	ZONE(S) 183	30-12-15
-	WING SUPPLY DUCT	ZONE(S) 183	30-12-17
-	INBOARD PICCOLO DUCT	ZONE(S) 523 ZONE(S) 623	30-12-19
-	MIDDLE PICCOLO DUCT	ZONE(S) 525 ZONE(S) 625	30-12-21
-	OUTBOARD PICCOLO DUCT	ZONE(S) 527 ZONE(S) 627	30-12-23
-	INBOARD SLIP JOINT	ZONE(S) 523 ZONE(S)623	30-12-25
-	OUTBOARD SLIP JOINT	ZONE(S) 525 ZONE(S) 625	30-12-27

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