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MAINTENANCE MANUAL

 BRAKE TEMPERATURE MONITORING SYSTEM - DESCRIPTION AND OPERATION
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 1.  General_______
 A.  The Brake Temperature Monitoring System supplies brake temperature indication on the EICAS display. Brake temperatures are shown on the gear synoptic and the gear maintenance page. The synoptic page comes into view on EICAS when you push the GEAR button on the EICAS panel (P10). The maintenance page comes into view on EICAS when you push "32 GEAR" under the "EICAS MAINT PAGES" menu on the CMC. The displays show brake temperatures as a one digit number between 0 and 9. The digits are inside the tires of the gear schematic on the displays. Normal temperatures are shown in white. High temperatures (5 and above) are shown in amber.
 B.  When a brake temperature increases above the indication level of 5 a BRAKE TEMP advisory message comes into view on the upper EICAS display. The gear synoptic can then be displayed on the lower EICAS to identify which brakes are hot and the temperature relative to the other brakes.
 C.  The Brake Temperature Monitor System gets power from the 28 v dc Bus 2 through a circuit breaker on the P180 DC Power Distribution Panel.
 D.  The Brake Temperature Monitoring System contains a brake temperature control unit, 16 brake temperature sensors, and 4 compensators.
 2.  Brake Temperature Monitor Unit (Fig. 1)______________________________
 A.  The brake temperature monitor unit (BTMU) gets analog signals from each brake temperature sensor and applicable brake temperature compensator. It changes the analog signals into digital signals that are proportional to the brake temperatures. The digital signals are transmitted to the Electrical Interface Units (EIU) where they become indication of brake temperature on the EICAS display.
 B.  The BTMU transmits the brake temperature indication information to EICAS via the EIUs. This information is represented on EICAS gear synoptic and maintenance pages as a one digit number (0 to 9) for each brake. Zero is equivalent to 349 degrees F (176 degrees C) or less. Nine is equivalent to 1450 degrees F (788 degrees C) or greater. The advisory "BRAKE TEMP" EICAS indication will come into view when the temperature of any brake increases to 900 degrees F (482 degrees C) or greater.
 With a S283U004-4 BTMU, a brake temperature sensor and/or compensator wire shorted to the structure will blank the EICAS brake temperature indications on the gear synoptic and maintenance pages, and display the status "BRAKE TEMP SYS" EICAS message.
 With a S283U004-5 BTMU, a brake temperature sensor and/or compensator wire shorted to the structure will blank the EICAS temperature indications for the brakes on that gear. Failure messages for that gear's four brake temperature sensors and associated temperature compensator will be recorded in the CMC. The EICAS indication of the remaining twelve brake temperatures will not be affected if no other failure exists.
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MAINTENANCE MANUAL

CENTER EQUIPMENT CENTER

H/A445-10
Brake Temperature Monitor Unit Location Figure 1
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MAINTENANCE MANUAL

 C.  The BTMU contains BITE (Built In Test Equipment) to help the line maintenance person isolate malfunctions in the Brake Temperature Indicating System. The line maintenance person uses the Central Maintenance Computer (CMC) to get data on malfunctions in the brake temperature indicating system.
　
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