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MAINTENANCE MANUAL
L PACK BACKUP TEMP CONTROL CARD
LEFT SYSTEM SHOWN, RIGHT SYSTEM SIMILAR
Pack Standby Control Operation
Figure 15 (Sheet 1)
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MAINTENANCE MANUAL
L PACK TEMP CONTROLVALVE
LEFT SYSTEM SHOWN, RIGHT SYSTEM SIMILAR
Pack Standby Control OperationFigure 15 (Sheet 2)
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MAINTENANCE MANUAL
OUTLET TEMP SENSOR 2PACK STANDBY TEMPERATURE CONTROLLER
LEFT SYSTEM SHOWN, RIGHT SYSTEM SIMILAR
Pack Low Limit Valve Standby Control
Figure 16
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2) In the STBY-C mode, the backup-temperature-control card causes the ram air doors to be fully open and the temperature control valve to be fully closed. The low-limit-control valve stays closed unless it is pneumatically opened.
(f) The OFF mode.
1) When the L or R PACK selector is OFF, the ram air inlet doors and the temperature control valve is controlled by the air/ground relays. When the airplane is on the ground, the ram air doors will be fully open and the temperature control valve will be fully closed. When the airplane is in the air, the ram air doors will be fully closed and the temperature control valve will be fully open. The low-limit-control valve will stay closed unless it is pneumatically opened.
2) Whenever the left or right flow control valve is closed, the applicable (L or R) PACK OFF light, on the P5 panel, will come on and the EICAS message L or R PACK OFF will be shown on the upper display.
B. Built-In-Test Equipment (BITE) (Fig. 17)
(1)
The automatic-pack-temperature controllers contain some built-in-test-equipment (BITE). The BITE monitors the cooling pack system for failures when the electrical power is on. It also stores the failure conditions for up to ten flights. BITE tests are used for maintenance to examine the BITE for failures. The BITE looks for two types of failures, critical and non-critical.
(a)
A critical failure is any major failure of the controller. When a critical failure occurs the fault relay latches, the CONTROLLER FAULT light comes on, and power is not supplied to the components which the controller controls. A critical failure occurs when one of these conditions occurs: 1) The watchdog timer senses that the software program
execution does not progress in the correct sequence and
time. 2) The internal power supply regulator fails. 3) The analog-to-digital input converter fails. 4) The read access memory (RAM) location fails.
(b) A non-critical failure is any partial failure of the controller or a component that is tested by the BITE. When a non-critical failure occurs, the controller continues to operate without the use of the failed part. The non-critical failure will be stored in the EAROM memory and can be recalled by the BITE test.
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