F88174
504 Wing Thermal Anti-Icing System Equipment Location
Jan 20/83 Figure 1 30-11-01
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
D. The valve control relay is located in the P5-11 module. The relay directs 115-volt ac power from the WING A/I circuit breakers to open the wing anti-ice control valves when de-energized and to close the valves when the relay is energized. The relay is controlled by transistorized circuitry in conjunction with the safety relay the control switch, two transistorized engine EPR switches and the ground overheat thermal switches.
E. The transistorized circuitry also controls the indicating lights.
F. The ground 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 approximately 125°C. Actuation of either switch, while the airplane is on the ground, 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.
504
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F88184
504 Wing Thermal Anti-Icing Simplified Circuit
Oct 20/90 Figure 2 30-11-01
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
B. Each valve indicating light is controlled by transistorized circuitry. The system control switch must be in ON position. 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. The wing anti-icing system may be operated continuously on the ground or inflight on airplanes with EPR actuated take-off warning system. Actuating the wing anti-ice switch to the ON position opens the wing TAI control valves and allows pneumatic air to flow through the wing leading edge anti-ice ducts. The wing leading edge is protected from overheat by two 125°C thermal switches which automatically close the wing TAI system shutoff valves. In addition, the wing TAI shutoff valves are automatically closed when the engine EPR in 1.4 or greater. The system will recycle the wing TAI system shut-off valves to the open position when the engine EPR is less than 1.4 and the air temperature is less than 125°C. During taxi and takeoff the wing anti-ice switch may be left in ON position but will automatically return to OFF position at airplane liftoff. In flight operation requires manual switching of the system.
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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