The wing anti-icing system does not let ice collect on the wing slats and leading edge. There are two equivalent anti-icing systems which operate independently. One system is for anti-icing of the left side of the wing and the other for anti-icing of the right side of the wing. Bleed air for the system on the left side is supplied by the left engine and bleed air for the system on the right side is supplied by the right engine.

The anti-icing system uses direct, not cooled, engine bleed-air from the bleed air system. The temperature changes with the aircraft speed, the altitude, the ambient temperature is usually between 350 °F and 650 °F (175 °C to 340 °C).

Each anti-icing system takes the airflow from its related bleed air system.

The airflow supplied to the wing anti-icing systems is adjusted by the anti-icing modulating-and-shutoff valves. These valves are controlled by the bleed management controller (BMC) to keep the wing temperature at 167 °F (70 °C) to not let the ice collect on the wing slats and leading edge. The BMC receives data from temperature sensors installed on the inner side of the wing leading edge.

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The anti-ice panel is part of the bleed/air conditioning and anti-ice panel and is located overhead in the cockpit. It contains two rotary selectors, which are applicable to the wing anti-ice system.

The wing selector has three positions:

OFF	Both wing anti-ice valves are closed independently of the BMC
AUTO	Wing anti-ice is switched on or off automatically by the ice detectors and the temperature is controlled by the two BMCs; this activation is inhibited on ground and during takeoff.
ON	Wing anti-ice is switched on independently of the ice detectors with skin temperature and valve configuration controlled by the BMC. This selection is used to operate the wing anti-ice in case of ice detector failures (ICE DETECTOR FAIL message on CAS) or on ground during takeoff.

The wing XBLEED rotary selector has 3 positions:

AUTO	In this position the operation of the cross bleed wing valve is controlled by the BMCs. Normally the cross bleed wing valve will be closed.
FROM L	The left wing anti-ice valve and the cross bleed wing valve are open, and the right wing anti-ice valve is closed; the two wings are supplied by the left engine bleed
FROM R	The right wing anti-ice valve and the cross bleed wing valve are open, and the left wing anti-ice valve is closed; the two wings are supplied by the right engine bleed

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Located on the EICAS primary page, below and outboard of the N1 indicator, is an annunciation of the associated wing's anti-ice system status. The WAI icon will change colors according to system status as follows:

Item	Green	Amber	White	Magenta	Red
WAI Icon (normally not visible)	Normal operation	WAI valve failed or cross-bleed operation	Engine not running	Invalid	Wing over-temperature

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The wing anti-ice synoptic page is combined with the bleed air and cowl anti-ice synoptic. The wing anti-ice synoptic displays:

Item	Green	Amber	White	Magenta	Red
Wing Anti-Ice and Cross bleed valves	- - -	Valve failed in position	Normal operation	Invalid	- - -
Wing Anti-Ice Ducts (Leading Edge)	Normal operation, otherwise empty	Low leading edge temperature detected	Initially activated(not up to normal temperature)		Over-temperature

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There are two anti-icing modulating-and-shutoff valves, one for each anti-icing system, installed in the belly fairing. Each valve has a valve body, pneumatic actuator and torque motor.

The valve has a three inch flange body, which is made from high-temperature stainless steel. The valve body has an upstream pressure orifice to supply the pneumatic actuator chamber. A butterfly is linked to the valve body through a shaft.

The torque motor adjusts the air pressure supplied to the pneumatic actuator chamber through a variable restrictor. The pneumatic actuator adjusts the position of the butterfly through the signal supplied by the BMC. This signal causes the valve to control the flow of bleed air. The opening and closing of the butterfly varies the airflow to the wing anti-ice system. This keeps a constant temperature of the leading edge at the location of the control sensor.

A microswitch operated by the butterfly shaft shows if the butterfly is open or closed.

The anti-icing modulating-and-shutoff valve is equipped with a thermal insulation muff. This muff covers the valve body and the attachment couplings, so that there is no exposed surface with a skin temperature higher than 200 °C (392 °F). The muff is tightened around the valve body by means of "Velcro" straps.

The anti-icing modulating-and-shutoff valve can be manually locked in the closed position for dispatch.

The BMC supplies a signal to the anti-icing modulating-and-shutoff valve. This signal causes the valve to control the flow of bleed air. This keeps a constant temperature of the leading edge at the location of the control sensor.

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The wing cross-bleed valve has a valve body and an electrical actuator. The wing cross-bleed valve has a three-inch flange body, which is made from high-temperature stainless steel. The wing cross-bleed valve is found in the belly fairing. It is an electrically operated isolation valve. A butterfly is attached to the valve body through a shaft. A manual control is supplied to set the valve to the OPEN or CLOSED position when it is not in operation. Two microswitches operated by the butterfly shaft, indicate if the butterfly is closed or open.

The wing cross-bleed valve connects the two anti-icing systems. This valve is usually closed and is used to supply both sides of the wing from one engine if one engine or system fails. When the wing cross-bleed valve opens, the related anti-icing modulating-and-shutoff valve automatically closes through the BMC. The anti-icing isolation valve can be controlled by either control channels of the BMC.

A thermal insulation muff protects the valve body and its attachment couplings. This muff covers the valve body and the attachment couplings, so that there is no exposed surface with a skin temperature higher than 200 °C (392 °F). The muff is tightened around the valve body by means of Velcro straps.

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There are four anti-icing temperature sensors, two per wing. The anti-icing temperature sensors are dual element sensors. Each sensor has two platinum resistance elements, with a pair of wires for each probe. The elements are encased in a stainless steel body.

The two inboard sensors, one per wing are installed on the inner surface of the inboard fixed leading edge, sense the wing temperature and control the necessary hot airflow demand through the anti-icing modulating-and-shutoff valves. A U-shaped Teflon cover is installed at the back of the inboard sensor to reduce the influence of bay internal temperature.

The inboard anti-icing temperature sensors are connected to the BMCs for the control of the wing anti-ice valves and overtemperature monitoring.

The inboard sensors consist of two elements (1 and 2). They are connected as follows:

• Sensing element 1 is connected to the control channel of its associated BMC, and is used for control and overtemperature monitoring
  
  
• Sensing element 2 is connected to the monitoring channel of its associated BMC, and is used for backup control, as well as overtemperature monitoring

The outboard sensors, installed on the inner surface of slat 4, monitor the wing temperature. The outboard temperature sensors monitor the wing anti-icing system operation. They supply the indication to the DAU and to the BMC if the outboard skin temperature is more or less than certain limits. The data supplied by the sensors is used by the BMC to send the appropriate messages to the EICAS display.

The outboard sensors consist of two elements (1 and 2). They are connected as follows:

• Sensing element 1 is connected to the DAU/ IAC, and is used for overtemperature and low temperature monitoring 
  
  
• Sensing element 2 is connected to the monitoring channel of its associated BMC, and is used for overtemperature and low temperature monitoring. For redundancy, it does not share any circuitry with the inboard element 2

Note:
More information on low temperature and overtemperature monitoring is provided in the Operation section (Abnormal Conditions).

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Automatic operation of the wing anti-ice system is controlled through the bleed management controllers.

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The anti-icing system uses direct, not precooled,engine bleed air from the bleed air system. The temperature changes with the aircraft speed, the altitude, and the ambient temperature and isusually between LP 77 °C to 277 °C (170 °F to 530 °F), HP 133 °C to 407 °C (271 °F to 764 °F). Each anti-icing system takes the airflow from its related bleed air system.

The airflow supplied to the wing anti-icing systems is adjusted by the anti-icing modulating-and-shutoff valves. These valves are controlled by the bleed management controller (BMC) to keep the wing temperature at 239 °F (115 °C) to not let the ice collect on the wing slats and leading edge. The BMC receives data from temperature sensors installed on the inner side of the wing leading edge.

The flow control is duplicated by the monitoring channel of the BMC, which operates through the second probe found in the body of the anti-icing temperature sensor. One BMC channel does the control function. The other channel monitors, but also controls if the first channel is defective.

Automatic Operation

The automatic mode of wing anti-ice is selected by positioning the WING ANTI-ICE switch to the AUTO position.

In this mode the ice detection system has full authority for detecting icing conditions and for activating the corresponding anti-icing circuits.

On ground and during takeoff (up to 400 ft. altitude), automatic switching of the system is inhibited to avoid bleed air flow changes and corresponding engine thrust setting changes. Manual operation is available anytime by selecting wing anti-ice to ON.

In flight, if one of the two ice detectors sends an "Ice Signal 3" signal, the wing anti-ice system is automatically activated. An independent signal is sent from each BMC to each WAIV, which is driven open.

The BMC reads the corresponding inboard temperature sensor connected to the control channel. This measurement is processed in the control channel and a drive current is applied to the torque motor of the corresponding WAIV.

The wing anti-ice system is switched off when the ice detectors indicate that no more ice is present. A 60-second time delay is built into the ice detector to allow the aircraft to fly in variable icing conditions without the icing system cycling on and off rapidly. Monitoring of the wing anti-ice is achieved by means of the BMCs, the inboard/outboard skin temperature sensors and the valve position switches.

Furthermore, the monitoring of the wing anti-ice leading edge overheat (warning message) is also performed by both inboard and outboard temperature sensors.

Manual Operation

Independently of the ice detectors, the wing anti-ice system can be activated by means of the anti-ice panel rotary selector. When the WING ANTI-ICE selector is set to the ON position, the wing anti-ice system is activated and control is still performed by the BMCs, using the wing temperature sensors. This position is selected for takeoff in case of icing risk (visible moisture and external temperature below 5 °C).

Wing Anti-Ice Cross Feed System

Both systems can be connected together by an anti-icing cross-bleed wing (CBW) valve. This valve is usually closed and is used to supply both sides of the wing from one engine if one engine or system is defective.

In case a failure occurs that necessitates crossbleed, the CBW will be automatically opened, and the relevant WAIV will be automatically closed by the BMC. The CBW can be controlled by either control channel of the BMCs.

Manual control of the wing anti-icing system is supplied through the WING XBLEED switch installed on the BLEED/AIR COND & ANTI-ICE control panel. When the WING XBLEED switch is set to FROM L, bleed air for the two wing anti-ice systems is supplied through the left engine bleed air system. At this time, the right side anti-icing modulating-and-shutoff valve goes to the closed position and the cross-bleed wing valve goes to the open position. When the WING XBLEED switch is set to FROM R, bleed air for the two wing anti-ice systems is supplied through the right engine bleed air system. At this time, the left side anti-icing modulating-and-shutoff valve goes to the closed position and the cross-bleed wing valve goes to the open position.

If the anti-ice system is operating under crossbleed conditions, that is to say both wings supplied by one WAIV and CBW open, the BMCs compare by X-talk the readings of left and right inboard temperature sensors, and the smallest value is used for control of the operating WAIV.

Abnormal Conditions

Low Temperature Monitoring

The monitoring for a low temperature condition is performed as soon as the anti-ice system is activated. Each BMC receives two temperature signals from the onside outboard anti-ice sensors. The two signals provide a parallel path to allow the BMC to determine the wing anti-ice low temperature condition.

The outboard anti-ice temperature sensor element 1 is processed by DAU and routed back to the BMC monitor channel (software function). This data is then used by the BMC monitor channel to perform the wing anti-ice low temperature monitor logic.

The outboard anti-ice temperature sensor element 2 is processed directly by the BMC monitor channel (hardware function). This data is then used by the BMC monitor channel to perform the BMC wing anti-ice low temperature monitor logic.

For redundancy, a third low heat monitor is provided by the IAC. The IAC logic uses the DAU (outboard element 1) temperature and the BMC WAI active signals to monitor for the wing low temperature condition.

The CAS message WING A/ICE LO HEAT will be posted if the wing cools down during operation or fails to heat up properly after activation.

The CAS message WING A/ICE LO HEAT will be posted if the wing cools down during operation or fails to heat up properly after activation.

Overheat Condition

The monitoring of the wing leading edge for overtemperature is performed in parallel as follows:

• Inboard anti-ice temperature sensor element 1 is processed by the control channel of its associated BMC
  
  
• Inboard anti-ice temperature sensor element 2 is processed by the monitor channel of its associated BMC
  
  
• Outboard anti-ice temperature sensor element 1 is processed by the DAU, and returned to the BMC monitor channel (software function)
  
  
• Outboard anti-ice temperature sensor element 2 is processed directly by the BMC monitor channel (hardware function)

For redundancy, a fifth overheat monitor is provided by the IAC. The IAC logic uses the DAU (outboard element 1) temperature and the BMC WAI active signals to monitor for the wing overheat condition.

When overheat is detected, the WAI system is automatically closed and a WING OVERHEAT warning is posted on EICAS. The warning can be generated by the BMC or the DAU/IAC. On receipt of the warning, the crew must select wing anti-ice to OFF on the control panel.

The warning will be canceled by:

• BMC
  When WAI selected OFF on control panel and wing leading edge temperature drops 10% below warning level or CBW and WAIVs are closed
  
  
• DAU
  When wing leading edge temperature drops below warning temp

The wing leading edge will be shown in red on the system synoptic as long as the warning is posted.

Sensor Failure/BMC Failure

If a failure of either the inboard sensor (element 1) connected to the control channel or the control channel itself of one BMC occurs, the monitoring channel of this BMC assumes control via the other inboard sensor (element 2).

If both inboard sensors or both lanes of the left BMC are inoperative, the right BMC will recognize the failure by cross-talking to the left BMC through the ARINC 429 data bus. It will then take over control of the left wing system operating through its control lane, its WAIV and its temperature sensor, with cross-bleed wing (CBW) valve open.

Note:
Right side failures would result in similar actions.

Automatic reconfigurations are latched until the crew confirms the automatic selections on the cockpit panel. Then the anti-ice fail caution message disappears and is replaced by a status message with the new system configuration.

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
MT113/MT126	ANTI-ICING MODULATING-AND-SHUT-OFF VALVES	ZONE(S) 171/172	30-11-01 [ GX ] [ GXRS ] [ G5000 ]
E38/E39/E40/E41	ANTI-ICING TEMPERATURE SENSORS	ZONE(S) 510/610	30-11-05 [ GX ] [ GXRS ] [ G5000 ]
L33	WING CROSS-BLEED VALVE	ZONE(S) 171/172	30-11-09 [ GX ] [ GXRS ] [ G5000 ]

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