737 AMM 飞机维护手册 防冰和排雨 ICE AND RAIN PROTECTION(21)

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2.  Window Conductive Coating
A.  The control cabin windows are of laminated glass-vinyl construction. Refer to Chapter 56, Control Cabin Windows, for details of window construction. The No. 1 and 2 windows have a conductive coating between the outer glass pane and vinyl core where it is most effective for window anti-icing, whereas the No. 4 and 5 windows have their conductive coating between the inner glass pane and the vinyl core where it will be most effective for window defogging. All four windows have electrical terminals connected to bus bars, which are molded into the upper and lower edges of the window in contact with the conductive coating. The windows are heated by allowing current to flow thru the conductive coating between the upper and lower bus bars. The resistance of the conductive coating increases with age and higher voltages are required across the bus bars to maintain equivalent heat output. The No. 1 window heaters have two series of fine wires imbedded in the vinyl. Each series of wires is electrically connected with the other in parallel. If one series fails, the remaining one provides approximately 50 percent of the heat provided when both are heating.
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3.  Window Heat Sensor
A.  The No. 1 and 2 windows each have a heat sensor consisting of a filament of non-insulated resistance wire. The wire is arranged in a single plane coil and imbedded in a thin plastic wafer installed near the lower edge of the window (Fig. 1 and 2), between the outer pane and plastic core. The resistance of the wire is sensitive to temperature and increases as the temperature increases. A change in window temperature causes a change in sensor resistance, providing a signal for the heat control unit. Some No. 1 and 2 windows have a spare heat sensor mounted adjacent to the heat sensor, which may be used if the original sensor has failed.
4.  Control Switches
A.  There are four window heat control switches, one for each of the No. 1 and 2 windows on each side of the cabin. The switches are four poled two position ON-OFF toggle switches and are on the overhead panel. The No. 4 and 5 windows are controlled by the respective left or right side window heat switch (Fig. 1 and 2).
5.  Control Unit
A.  There are four window heat control units, one for each of the window No. 1 and 2 heating systems. The units are located in the E3-3 electrical rack (Fig. 1 and 2).
B.  The temperature control unit is a solid state device which performs three functions; overheat control, temperature control including ramp control and shorted sensor protection, and power indication.
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C.  The control unit overheat circuit when energized directs 115-volt ac power from the window anti-ice circuit breaker to the control unit temperature control circuit.
D.  The terminal strip on the E3-3 electrical shelf is provided a selection of voltages from an autotransformer within the control unit to suit the resistance of the conductive coating on the windows. Selection of voltage is accomplished by moving the window power lead to the appropriate tap on the terminal strip located on the outboard end of the control unit tray.
6.  Indicating Lights
A.  There are two indicating lights for each of the No. 1 and 2 window heating systems; one is for power indication and the other is for overheat indication. The circuit for the overheat indication also controls a master caution indicating circuit for the anti-ice (A/I) and master caution annunciators on the pilots' lightshield (Fig. 1). Both indicating lights are located adjacent to their respective control switch on the overhead panel; and the master caution control circuit is on three printed circuit cards mounted behind the panel. The lights receive 28-volt dc power from the IND LIGHTS circuit breaker on the No. 1 and 2 DC bus, and the master caution control circuit receives 28-volt dc power from the window heat control circuit breaker on Bus No. 2 (Fig. 3). The lights are of the press-to-test type and may be tested individually or through the use of the master light test switch. The lights may also be dimmed through the use of the master dim switch. Refer to Chapter 33, Master Warning and Caution Lights, for master caution lights, and the master dim and test switches.
　
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