E. Hydraulic fuses
(1)
The fuse prevents brake applications from draining a hydraulic system of fluid through a broken hydraulic line down stream of the fuse. The fuse automatically stops all flow if the volume of fluid passing through the fuse is too great. The fuse automatically resets within 5 seconds if the difference in pressure across the fuse is 18 - 30 psi.
(2)
The fuse can be reset manually by turning the reset knob. This permits fluid to pass around the fuse to make equal pressure on each side. When the reset knob is released a spring pushes it back to the closed position. A slot in the knob gives visual indication of the position of the knob.
F.
Brake Source Select Valve Fuse
(1)
This fuse is installed in the pressure line from system 4 to system 2 brake source select valve. This fuse will prevent the loss of system 4 in the event of a failure occurs in the system 2 brake source select valve.
G.
Accumulator Isolation Valve fuse
(1)
This fuse is installed in the pressure line between the alternate brake pressure source and the accumulator isolation valve. This fuse will prevent the loss of the alternate system brake pressure in the event a failure (failure caused by tire burst) occurs between the outlet of the fuse and accumulator isolation valve.
H.
Hydraulic filters
(1)
Two filters are installed in the antiskid module. One filter is in the metered pressure inlet and the other in the system pressure inlet. These permit only filtered fluid into module housing to prevent clogging.
I.
Shutoff valve
(1)
A shutoff valve prevents hydraulic system 4 pressure from being supplied to the first stage of the antiskid valve without metered pressure input of 260 psi or more. When metered pressure is more than 260 psi the shutoff valve passes system pressure to the first stage of the antiskid valve. When metered pressure decreases below 240 psi the a slide in the shutoff valve moves and replaces system pressure with metered pressure to the first stage of the antiskid valve.
5. Antiskid Module (Alternate) (Fig. 4)
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A
747-400 MAINTENANCE MANUAL
SEE A
SEE A
ANTISKID VALVE, ALTERNATE WING GEAR SYSTEM PRESSURE PRESSURE METERED
V35 (LEFT) OR V37 (RIGHT) FILTER
ALTERNATE BODY GEAR
ANTISKID VALVE,
V36 (LEFT) OR V38 (RIGHT)
ALTERNATE WING GEAR
ANTISKID VALVE,
V129 (LEFT) OR V132 (RIGHT)
ALTERNATE BODY GEAR
ANTISKID VALVE,
V130 (LEFT) OR V131 (RIGHT)
SCREEN FILTER
SUPPORT BRACKET
FUSE (2 LOCATIONS) RETURN LINE
A
Alternate Antiskid Module Assembly - Location Figure 4
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A
747-400
MAINTENANCE MANUAL
A. The Alternate antiskid system uses four antiskid modules, one for for each main landing gear. Each alternate antiskid module contains 2 antiskid valves, one for each axle wheel pair on the landing gear truck. The alternate antiskid modules for the body gear are on the aft bulkhead of the body gear wheel well above the body gear trunion. The alternate antiskid modules for the wing gear are on the forward bulkhead of the body gear wheel well.
B. Each alternate antiskid module contains these parts:
-
2 antiskid valves, all the same type
-
2 hydraulic fuses, all the same type
- one inlet filter
-
and a check valve.
C.
The alternate antiskid module assembly can be replaced as a unit or any of the components given above can be removed and serviced or replaced as necessary.
D.
Antiskid valves
(1)
The antiskid valves for the alternate antiskid module are the same as the antiskid valves for the normal antiskid module. The alternate system antiskid valves operate the same as the antiskid valves in the normal antiskid module except that there is no shut off valve. Thus system pressure operates the first stage of the valve at all times.
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