777 AIRCRAFT MAINTENANCE MANUAL
WING ANTI-ICE -WAI VALVE
EFFECTIVITY BEJ ALL 30-11-00
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D633W101-BEJ Jan 05/2002
WING ANTI-ICE -WAI PRESSURE SENSOR
Purpose
The WAI pressure sensor gets input from the air pressure in the WAI duct after the WAI valve. The center ACIPS card uses the pressure information to control the WAI system.
Physical Description
The WAI pressure sensor has a pressure line connector on one end and an electrical connector on the other end.
Location
The sensor is installed above the WAI duct in the leading edge of the wing. The access panel for the sensor is on the bottom surface of the wing leading edge next to the outboard side of the engine strut.
EFFECTIVITY BEJ ALL 30-11-00
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D633W101-BEJ Jan 05/2002
777 AIRCRAFT MAINTENANCE MANUAL
WING ANTI-ICE -WAI PRESSURE SENSOR
EFFECTIVITY BEJ ALL 30-11-00
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D633W101-BEJ Jan 05/2002
WING ANTI-ICE -WAI DUCTS
Purpose
The WAI ducts move air from the pneumatic system to leading edge slats which are outboard of the engines.
Physical Description
Some of the WAI ducts are perforated. The holes allow air to flow into the space in the leading edge slats. The air leaves the slats through holes in the bottom of each slat.
Some of the WAI ducts can telescope. Each telescoping duct has two sections. One section is to a duct in the wing. The other section attaches to a duct in the leading edge slat. The sections can move into each other. This permits the duct to extend or retract when the slat extends or retracts.
Locations
The perforated ducts are inside these slats:
*
3, 4, and 5 on the left wing
*
10, 11, and 12 on the right wing.
The ducts that can telescope are in the wings and in these slats:
*
6 on the left wing
*
9 on the right wing.
Access
There are duct joints between adjacent slats. The inboard and outboard end of each slat has an access panel for the duct joints between adjacent slats.
There is an access panel in the slat for the telescoping duct.
EFFECTIVITY BEJ ALL 30-11-00
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D633W101-BEJ Sep 05/2002
777 AIRCRAFT MAINTENANCE MANUAL
WING ANTI-ICE -WAI DUCTS
EFFECTIVITY BEJ ALL 30-11-00
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D633W101-BEJ Jan 05/2002
WING ANTI-ICE -FUNCTIONAL DESCRIPTION -ELECTRICAL
General
The WAI ACIPS control card controls both wing anti-ice valves. The required positions of the WAI valves change as bleed air temperature and altitude change. The left and right valves operate at the same time to heat both wings equally. This keeps the airplane aerodynamically stable in icing conditions.
The WAI pressure sensors supply feedback information to the WAI ACIPS card for WAI valve control and position indication. If either pressure sensor fails, the WAI ACIPS card sets the related WAI valve to either fully open or fully closed. If either valve fails closed, the WAI card keeps the other valve closed.
The WAI ACIPS control card receives ice detector data from the systems ARINC 629 buses. The data comes from the left and right ice detectors through the EAI ACIPS control cards.
There is one selector for the WAI system. The selector has three positions: AUTO, ON, and OFF.
Operational Modes
With the selector in AUTO and no operational mode inhibits, the WAI ACIPS card sends a signal to open the WAI valves when either ice detector finds ice. The valves close after a three minute delay when the ice detector no longer finds ice. The time delay prevents frequent on/off cycles during intermittent icing conditions.
See the ice detection system for more information about the ice detectors (SECTION 30-81).
With the selector ON and no operational mode inhibits, the wing anti-ice valves open. With the selector OFF, the wing anti-ice valves close.
Operational Mode Inhibits
The operational mode for the WAI valves, can be inhibited by many different sets of conditions.
.The operational mode is inhibited if all of the these conditions occur:
*
AUTO mode is selected
*
Takeoff mode
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