(b)
Push the line select key (LSK) that is adjacent to <CMC to show the CMC MENU.
(c)
If <RETURN shows after you push the LSK, push the LSK that is adjacent to <RETURN until you see the CMC MENU.
(d)
Push the LSK that is adjacent to <GROUND TESTS to show the GROUND TESTS menu.
(e)
Push the NEXT PAGE key until you find <29 HYDRAULIC POWER.
(f)
Push the LSK that is adjacent to <29 HYDRAULIC POWER to show the GROUND TESTS menu for the hydraulic system.
S 865-002
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747-400 MAINTENANCE MANUAL
(g)
Push the NEXT PAGE key until you find <HYQUIM.
E.
HYQUIM Ground Test
S 745-020
(1) Push the LSK that is adjacent to <HYQUIM.
NOTE: IN PROGRESS shows during the test.
____
S 745-006
(2) When IN PROGRESS goes out of view, look for PASS or FAIL> adjacent to <HYQUIM.
NOTE: If a PASS indication shows, no failures occured during
____
the test.
(a) If FAIL> shows: 1) Push the LSK that is adjacent to FAIL> to see the GROUND TEST MSG pages for the failure. 2) Push the NEXT PAGE key until you find all the GROUND TEST MSG pages. 3) Make a list of all CMCS messages, CMCS messages numbers, and ATA numbers that show on the GROUND TEST MSG pages.
4) Go to the CMCS Message Index of the Fault Isolation Manual (FIM) to find the corrective action for each CMCS message.
F. Put the Airplane in Its Usual Condition.
S 865-008
(1) Remove the electrical power if it is not necessary
(AMM 24-22-00/201).
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747-400 MAINTENANCE MANUAL
HYDRAULIC LOW PRESSURE WARNING SYSTEM - DESCRIPTION AND OPERATION
_________________________________________________________________
General
_______
A. The hydraulic low pressure warning system gives a visual warning when the pressure in any of the hydraulic pumps becomes too low. It also gives a visual warning when the system pressure becomes too low. The hydraulic control module is installed on the P5 panel in the flight compartment. It has a PRESS light for each of the four engine-driven pumps (EDP's) and the four demand pumps. There is also a SYS FAULT light on the hydraulic control module for each hydraulic system.
Hydraulic Low Pressure Warning Switch (Fig. 1)
_____________________________________
A. There are two low pressure switches for each hydraulic system. They are installed on the pressure module in the nacelle strut. One switch measures EDP pressure and one switch measures demand pump pressure.
B. There is a pressure transmitter installed downstream of the pressure module on each system. The pressure transmitters for systems 1 and 4 are installed in the right body gear well. The pressure transmitters for systems 2 and 3 are installed in the applicable wing gear well.
Operation (Fig. 2)
_________
A. Functional Description
(1)
The switches send a signal to the hydraulic interface module (HYDIM) when the hydraulic pump pressure decreases below 1,400 psi for more than two seconds. The HYDIM sends the signal to the EICAS interface unit (EIU) and the hydraulic control module. The EIU then sends the signal to the auxiliary EICAS display.
(2)
If a demand pump pressure is low, the applicable amber HYD PUMPS DEMAND PRESS light will go on. If the EDP pressure is low, the applicable amber HYD PUMPS ENGINE ENGINE PRESS light will go on.
(3)
The HYDIM monitors the signals from the pressure transmitters. When a system pressure is less than 1200 psi for more than 2 seconds, the SYS FAULT light comes on. The SYS FAULT condition continues until the system pressure increases above 1300 psi.
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