F87998
570  Wing Thermal Anti-Icing System Equipment Location 
Feb 15/78  Figure 1  30-11-0 
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

D.  The valve control relay is located behind the P5 overhead panel. The relay directs 115-volt ac power from the WING A/I circuit breakers to open the wing anti-ice control valves when energized and to close the valves when the relay is de-energized. The relay is controlled by the safety relay and the control switch.
E.  The transistorized circuitry is used to control the indicating lights, and in the event a ground overheat condition occurs, it also controls the valve control relay. The system can be tested on the ground and in the air.
F.  The overheat thermal switches are located at the root end of each wing leading edge distribution manifold. The switch is a temperature sensitive bimetallic type switch with normally open contact points, which close at the correct temperature. Thermal switches with part numbers 975-0062-002 or 3000-46-27 close at 125 degrees C (257 degrees F). Thermal switches with part numbers 975-0062-001 or 3000-46-28 close at 93 degrees C (200 degrees F). Actuation of a thermal switch in either wing while the switch is in the TEST or OFF position will complete a circuit to close both wing anti-ice valves.
5.  Wing Anti-Ice Indicating Components
A.  The wing anti-ice system is provided with a blue light for each control valve to indicate valve position. The lights are of the press-to-test type and are located on the overhead panel adjacent to the system control switch. The valve open indicating lights are illuminated dimly whenever their respective valve is in the open position, and brightly whenever their respective valve position does not agree with the control switch position due to a system malfunction or during valve transit. The lights may be tested through the use of the master light test switch. Refer to Chapter 33, Control Cabin Lighting, for the master test switch.
523 
30-11-0 Page 4  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Oct 20/91 

F88045
533  Wing Thermal Anti-Icing System Circuit 
Aug 15/76  Figure 2  30-11-0 
Page 5 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

B.  Each valve indicating light is controlled by a transistorized control switch, two poles of the system control switch, and the valve position limit switches in its respective control valve. The transistorized control switches are on printed circuit cards mounted behind the overhead panel. The transistorized light control switches are supplied 28-volt dc power from the A/I control circuit breaker.
6.  Operation
A.  The wing anti-icing system is controlled manually by the wing anti-ice control switch on the overhead panel. Actuation of the control switch to the ON position while the airplane is in flight opens the wing TAI control valves and allows pneumatic air to flow through the wing leading edge anti-ice ducts. The landing gear safety relay prevents wing anti-ice operation with the switch in the ON position while the airplane is on the ground. The wing TAI control valves may be operated for testing on the ground or in the air by holding the control switch in the GRD TEST position. Overheating of the ducts by excessive ground testing is prevented by the duct overheat switches, which will automatically cycle the control valves to prevent the pneumatic air from exceeding 200°F.
B.  The valve position indicator lights provide an indication of their respective valve position. The light will glow bright if the valve position disagrees with the control switch position. The light will glow dim if the valve is open and the control switch position is in either ON or TEST positions. The light will not illuminate if the valve is closed and the control switch is in the OFF position.
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WING ANTI-ICING SYSTEM - TROUBLE SHOOTING
EFFECTIVITY
Airplanes without Wing TAI System Ground Operation Capability
1.  General
A.  Before using the following trouble shooting chart prepare to test the wing TAI system in accordance with adjustment test procedure. Proceed with test to extent practical to determine extent of trouble. When checking system for air mode of operation press GRD SENSING TEST switch on landing gear module.
2.  Trouble Shooting Chart
Jun 20/84 30-11-0 Page 101
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