WINDOW
CONTROL
OVERHEAT THERMOSTAT
THERMOSTAT
C
NOTE: LEFT SIDE WINDOWS THERMOSTATSSHOWN, RIGHT SIDE WINDOWS
B
THERMOSTATS SIMILAR
Flight Compartment Window Anti-Ice System Component Location
Figure 1
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C. When window heat is activated from the flight deck, the control unit gradually applies increasing power over a 6-minute period, stopping when full power is reached or when window operating temperature is attained.
D. Each window heat control unit continuously monitors system operation. The control unit watches for power source failures, open or short circuits in the heater or sensor, and faults on the ARINC 429 data bus between the control unit and the EIUs. Any failure will remove power from the window, turn on the INOP light in the WINDOW HEAT switch, and cause an EICAS advisory message to be displayed.
E. A ground test can be performed with the CMC. Conclusion of the test is indicated by momentary illumination of the INOP light. If a failure is found during the ground test, a specific fault message will be displayed on the CDU and the window heat control unit must be reset by pressing the control switch off then ON.
NOTE: To do a CMC ground test, the airplane must be on the ground and
____ the TEST ENABLE switch (P461 overhead maintenance panel) must be in the TEST position.
F. Each window heat control unit has an input from the air/ground relay system. The control unit uses the air/ground status to allow a CMC ground test of the window heat system only when the airplane is on the ground. When the airplane is in the air, the control unit inhibits the CMC ground test.
4. No. 1 Left and Right Windows
____________________________
A. The No. 1 windows are located directly in front of the pilots. The heating element in each window is a conductive coating material laminated between the outer layer of hardened glass and the first inner layer of plastic. Two thermistor control sensors are also laminated in each window. One of the sensors is a spare which can be connected if the original sensor fails.
5. No. 2 and 3 Windows, Thermostats and Relays
___________________________________________
A. The No. 2 and 3 windows are located to the sides of the pilots. The heating element for each window is a conductive coating material laminated inside the window. The control thermostat for each window is installed on the inside surface of the windowpane and is held in place by a rat-trap type spring. The overheat thermostat for each of these windows is held against the inside surface of the window by a spring retainer. The relays which control the thermostats and which sense system faults are located in the P414 circuit breaker relay panel in the main electrical equipment center.
6. Operation (Fig. 2, 3)
_________
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MD&T SHELF
NOTE: NO. 1 LEFT WINDOW HEAT SYSTEM SHOWN,NO. 1 RIGHT SYSTEM SIMILAR.
E1-4 ELECTRONICS SHELF
No. 1 Window Heat System Schematic Figure 2
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P415 RIGHT POWER DISTRIBUTION CENTER
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