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system operation is automatic. When ice is detected, bleed air opens the nacelle
anti–ice valve and bleed air is supplied to the engine cowl inlet.
When ice is no longer detected, the nacelle anti–ice valve closes and bleed air is
no longer supplied to the engine inlet cowl.
Nacelle Anti–Ice System Manual Operation
On the ground and in flight, when the NACELLE ANTI-ICE switch is ON, bleed
air opens the nacelle anti-ice valve and bleed air is supplied to the engine inlet
cowl.
Nacelle Anti-Ice Non-normal Operation
Bleed air is not available for nacelle anti-ice operation when the pressure
regulating valve (PRV) has been closed due to a bleed air overheat, HP bleed valve
failed open, or if the start valve is not closed.
• automatic ice detection
• engine anti–ice
• wing anti–ice
• flight deck window heat
• windshield wipers
• probe heat
April 01, 2001
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
3.20.2 D6-30151-425
Anti-Ice, Rain -
System Description
When nacelle anti-ice is commanded on with the engine bleed valve closed, the
HP bleed valve remains closed. Bleed air is supplied by IP bleed only.
Nacelle Anti–Ice SystemSchematic
DUCT
BLEED AIR
START
LOGIC
SYSTEM
PRV
SIMILAR
N_O_T_E_: ALL ENGINES
ANTI-ICE
NACELLE
HP BLEED
IP BLEED
SYSTEM
LOGIC
ICE DETECTOR
ON
OFF
AUTO
NACELLE ANTI-ICE
1
2 3
4
October 1, 2000
747 Operations Manual
Anti-Ice, Rain -
System Description
Copyright © The Boeing Company. See title page for details.
D6-30151-425 3.20.3
Wing Anti–Ice System
The wing anti–ice system provides bleed air to each wing. When anti-ice is
commanded on, a valve opens in each wing, allowing bleed air to flow from the
engines to a spray tube in the leading edge. Wing anti–ice is inhibited in flight
when leading edge flaps are extended and on the ground.
The wing anti–ice indicationWAI is displayed beside the respective wing EICAS
N1 indication when the wing anti–ice valve is open.
Wing Anti–Ice System Automatic Operation
In flight, when the WING ANTI-ICE switch is in AUTO and the leading edge
flaps are retracted, wing anti–ice system operation is automatic. When ice is
detected, the wing anti–ice valves open and bleed air is supplied to the leading
edges. When ice is no longer detected, the wing anti–ice valves close and bleed air
is no longer supplied.
Wing Anti–Ice System Manual Operation
In flight, when the WING ANTI-ICE is ON and the leading edge flaps are
retracted, the wing anti–ice valve in each wing opens.
Flight DeckWindow Heat
All flight deck windows are electrically heated. The forward windows have
exterior surface anti–icing, and interior surface antifogging protection. The side
windows have interior surface antifogging protection only.
The window heat switches control heating for the windshields only. With the
WINDOW HEAT switches ON, electric power is supplied to the windshields.
Electric power for the windshields modulates to maintain a constant temperature.
Side window heating is automatic and no flight deck controls are provided.
Electric power is applied to the side windows whenever the AC electrical system
is powered. Power for the side windows is thermostatically controlled.
Power is removed from the system if a fault or overheat condition is sensed.
Pushing a WINDOW HEAT switch off for 10 seconds, then ON, resets a
windshield heat controller fault.
Windshield Air
Air for anti-fogging is drawn from the flight deck conditioned air supply and
directed across the windshields.WSHLD AIR switches on the Captain’s and First
Officer’s auxiliary panels turn on anti-fogging air to the related windshields.
April 01, 2001
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
3.20.4 D6-30151-425
Anti-Ice, Rain -
System Description
WindshieldWipers and Washers
The Captain’s and First Officer’s windshields are equipped with independently
controlled, two speed windshield wipers.With aWIPER selector in OFF position,
the related wiper is off and stowed.
Scratching of the windshield surface may occur if the wipers are used on a dry
windshield.
The Captain’s and First Officer’s windshields are equipped with a windshield
washer system. Windshield Washer switches command a continuous application
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