The wing anti-ice system uses hot air from the high pressure bleed-air system. The air goes through insulated ducts to the wing roots. At the forward part of the wing roots, the air goes through piccolo tubes along the wing leading edges to the end of the wings. Piccolo tubes supply hot air to the inner surface of the wing leading edges.

The anti-ice system controls hot air supplied from the engines to the wing anti-ice system. If there is a loss of one hot air supply, the anti-ice system has a crossflow function. This crossflow function supplies the opposite side wing anti-ice system from the remaining air supply.

The temperature of the air is controlled by the temperature sensors, the integrated air system (IAS) controller, and the valves.

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The inboard leading-edge temperature sensor has a two channel configuration and is attached to the inner surface of the leading edge skin. There is one sensor for each leading edge installed near the wing root adjacent to a rib at WS50.79. The inboard leading-edge temperature sensor is used to control the anti-ice airflow and to monitor high temperatures. The temperature control is set at 54 °C (129.20 °F). The temperature of an overheat condition is set at 74 °C (165.20 °F) for four minutes or 84 °C (183.20 °F) for four seconds. Each channel of the sensor is connected to a different IAS controller.

Each sensor is made of two platinum resistance probes (PT500 type) with a pair of wires for each probe. The length of the probe wires between the probe and the IAS controllers does not change the precision of their detection. They are contained in a stainless steel casing. There is a clearance between the probes and the aft face of the casing. This decreases the effect of the ambient temperature on the leading edge skin which is sensed. Also, there is a cover on the top of the temperature sensor to decrease the effect of the anti-ice air jet.

The inboard leading-edge temperature sensor sends its data output to the IAS controller which sends it to the data concentrator unit (DCU). The IAS controller calculates the value of the signal and sends a control signal to open or close the related wing anti-ice valve (WAIV). If an overheat condition is sensed, the IAS controller will send a signal to the DCU. The DCU uses this signal to show a warning message on the display of the engine indication and crew alerting system (EICAS).

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The outboard leading edge-temperature sensor has a two channel configuration and is attached to the inner surface of the leading edge skin. There is one sensor for each leading edge installed near the wing tip adjacent to a rib at WS360.20. The outboard leading-edge temperature sensor is used to monitor low temperatures. In flight, the temperature of a low temperature condition is set at 29 °C (84.20 °F) for 30 seconds. On the ground, the temperature of a low temperature condition is set at 25 °C (77 °F) for 30 seconds. Each channel of the sensor is connected to a different IAS controller.

Each sensor is made of two platinum resistance probes (PT500 type) with a pair of wires for each probe. The length of the probe wires between the probe and the IAS controllers does not change the precision of their detection. They are contained in a stainless steel casing. There is a clearance between the probes and the aft face of the casing. This decreases the effect of the ambient temperature on the leading edge skin which is sensed. Also, there is a cover on the top of the temperature sensor to decrease the effect of the anti-ice air jet.

The IAS controller sends a low temperature data output from the outboard sensor to the stall protection computer (SPC) and the DCU. The SPC uses the data to calculate the stall protection tables. The DCU uses the data for the EICAS and Synoptic page indications.

The WAI LOW TEMP 1 discrete signal is:

• Supplied by the IAS controller No. 1
• Sent to the SPC channel A
• Sent to the DCU.

The WAI LOW TEMP 2 discrete signal is:

• Supplied by the IAS controller No. 2
• Sent to the SPC channel B
• Sent to the DCU.

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The wing cross-bleed valve (CBV) is found in the belly fairing, downstream of the wing anti-ice valves (WAIV). The wing CBV gives a connection between the right and left sides of the anti-ice system. When the wing CBV is opened, one source of bleed air can supply the two sides of the anti-ice system.

The wing CBV has the internal parts that follow:

• A butterfly plate
• A pneumatic actuator
• A diaphragm
• An opening spring
• A vent screw
• An overpressure clapper
• A solenoid valve
• A pressure reducer
• A pneumatic port for the sense line.

The valve body is a 2 in. (5.08 cm) stainless steel valve. The wing CBV is a pneumatically operated butterfly valve. The wing CBV is controlled by the two IAS controllers. The solenoid valve is controlled by a 28 VDC signal. There is a microswitch which sends a signal to the EICAS to show the fully closed position of the butterfly plate.

The valve can also be overridden manually. This lets the valve be mechanically set and locked in the opened 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.

When there is no bleed air pressure from the engine, the wing CBV is in the fully opened position. When the bleed air pressure is more than 11 psi (75.84 kPa) and the solenoid is energized, the wing CBV moves to the fully closed position. When the solenoid is not energized, the wing CBV moves to the fully opened position. The wing CBV senses the bleed-air pressure upstream of the right WAIV thru a sense line. The valve can be mechanically set and locked in the opened position while it is installed. The valve is spring-loaded to the fully opened position.

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The wing CBV sense line is connected between the wing CBV in the belly fairing and the right bleed pipe. It makes sure that there is sufficient air pressure to operate the wing CBV. The sense line gets its pressure from a source upstream of the right WAIV.

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The ANTI-ICE control panel is found in the flight compartment on the center pedestal. It has a pushbutton annunciator (PBA) and a rotary switch to control the wing anti-ice system. It also has PBAs to control the anti-ice to the engine nacelle, windshield, side windows and the air data probes. During usual operation, the lights in the PBAs are extinguished and do not come on automatically. The lights come on when the PBAs are pushed and go out when they are pushed again. When the lights come on, the legends in the PBAs show the status of the related anti-ice components.

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The anti-ice system is divided into left and right sides. The left wing is supplied from the left engine and the right wing from the right engine. The two sides are the same and connect to the opposite side by a crossflow duct. The left and right sides are isolated by the wing CBV.

The anti-ice system controls the hot air from the engines to the wing anti-ice thru the different ducts. The inboard leading-edge temperature sensors are used to monitor and control the wing anti-icing system. They make sure that the leading edge temperature is sufficient for correct anti-ice functions and that no damages occur to the structure. The air flow is controlled by the IAS controllers with the output of the leading-edge temperature sensors.

In usual operation, the WING SOURCE switch is set to NORMAL on the anti-ice control panel. This sets the wing CBV to the fully closed position. The bleed air is supplied from each engine to its related side of the aircraft.

With the WING SOURCE switch set to NORMAL, when the WING PBA is pushed, the light comes on. This lets the two high pressure valves and WAIVs to open or close as required to keep the temperature in the operational range. When the WING PBA is pushed again, the light goes out. This sets the two high pressure valves and WAIVs to the fully closed position, and sets the wing CBV to the fully opened position.

If only one source of bleed is available, the WING SOURCE switch on the anti-ice control panel is set to FROM L or FROM R. This sets the wing CBV to the fully opened position and air is supplied from one engine to the two wings. When the WING SOURCE switch is set to FROM L, the right high pressure valve and WAIV are set to the fully closed position. When the WING SOURCE switch is set to FROM R, the left high pressure valve and WAIV are set to the fully closed position.

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

The L (R) WING OVERHEAT warning message will show when an overheat condition is sensed by the left (right) inboard leading-edge temperature sensor.

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 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 SOURCE-XBLEED advisory message will show when the wing CBV is in the fully opened position, the WING SOURCE switch is set to NORMAL and the anti-ice system is on.

The WING SOURCE-XBLEED status message will show when the wing CBV is in the fully opened position, the WING SOURCE switch is not set to NORMAL and the anti-ice system is on.

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

EICAS MESSAGE(S)	LEVEL (COLOR)
L WING OVERHEAT	WARNING (red)
R WING OVERHEAT	WARNING (red)
L WING ANTI-ICE FAIL	CAUTION (amber)
R WING ANTI-ICE FAIL	CAUTION (amber)
WING ANTI-ICE FAULT	CAUTION (amber)
WING ANTI-ICE FAULT	ADVISORY (cyan)
WING SOURCE-XBLEED	ADVISORY (cyan)
WING SOURCE-XBLEED	STATUS (white)
L WING A/I LOW TEMP	CAUTION (amber)
R WING A/I LOW TEMP	CAUTION (amber)

The status of the wing CBV is shown on the ANTI-ICE synoptic page. The wing CBV is shown with a fix 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 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

 

Bleed Leak Detection System – Anti-ice Leak

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PBIT

The IAS controllers do a power-on built-in test (PBIT) which include the test of some components of the anti-ice system.

The test looks at the range and precision of the output of the temperature sensors.

CBIT

The IAS controllers do a continuous built-in-test (CBIT) which include the test of some components of the anti-ice system. The IAS controllers continuously monitor the temperature read by each channel of the inboard and outboard temperature sensors. The IAS controller's also monitor each channel of the sensors for drift in the temperature read.

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Component Location Index
IDENT	DESCRIPTION	LOCATION	IPC REF
MT41	INBOARD TEMPERATURE SENSOR (LH)	ZONE(S) 523	30-11-01
MT32	INBOARD TEMPERATURE SENSOR (RH)	ZONE(S) 623	30-11-01
MT43	OUTBOARD TEMPERATURE SENSOR (LH)	ZONE(S) 527	30-11-03
MT34	OUTBOARD TEMPERATURE SENSOR (RH)	ZONE(S) 627	30-11-03
MPE10	WING CROSS-BLEED VALVE	ZONE(S) 182	30-11-05
-	WING CROSS-BLEED VALVE SENSE LINE	ZONE(S) 182	30-11-07
PL19	ANTI-ICE CONTROL PANEL	ZONE(S) 210	30-11-09

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