TM
55-1730-229-34
AG
320A0-MME-000
TO
35C2-3-473-2
TM
1730-34/1
d r a u l i c fluid when either the load valve
(3) The pump provides hydraulic
i s closed or when hoses to the aircraft
pressure as commanded by the PRESSURE
The two pressure
switch , f i g u r e F O - 9 .
(or dual manifold) are not connected.
Restrictions in the HIGH PRESSURE BYPASS
c o m m a n d lines to the pump carry 28 vdc
valve line and in the dual manifold
w h i c h positions the pressure adjustment
bypass lihe provide a backpressure of
mechanism inside the pump. W h e n output
5 0 0 psi when the bypass valve is open.
c o n n e c t o r pin G is at 28 vdc (pin H is
T h i s back-pressure is required for prop-
the return) the pump mechanism operates
e r pump operation. A p p l i c a t i o n o f h y -
When the applied
t o inc r e a s e p r e s s u r e .
draulic power to the aircraft is con-
v o l t a g e is reversed on the pump input
leads, the mechanism operates to de-
trolled by the load select valve. As
The PRESSURE switch
shown in figure 8-4, operation of the
crease pressure.
i s s p r i n g loaded to its unconnected
load select valve involves three steps
So the pump pressure
a s follows:
center position.
m e c h a n i s m remains in the last position
( a ) . OUTPUT switch S4 is set to
it was set to by the operator unless
ON which applies 28 vdc to the pilot
p o w e r to the hydraulic module is turned
off.
When POWER switch S1 is set to
valve solenoid and OUTPUT ON indicator.
OFF, output connector pin H is connected
( b ) . Activation of the solenoid
t o 28 vdc and pin G becomes the return
This causes the pump pressure
line.
pushes the pilot valve against the
mechanism to move to the position of
spring allowing high pressure fluid to
b e applied to the load valve.
minimum pressure (500 psig).
( c ) . Fluid pressure pushes the
(4) Prior to servicing an aircraft
load valve against its spring allowing
the PRESSURE RELIEF valve (figure FO-10)
h y d r a u l i c system output to be applied to
the aircraft.
is set to the maximum allowable pressure
If the
for that particular aircraft.
operator increases the pump pressure be-
( 7 ) When the OUTPUT switch is set
t o OFF, t h e s o l e n o i d , p i l o t a n d l o a d
yond the allowable maximum, the PRESSURE
RELIEF valve will open to prevent excess
valves all return to their original po-
sitions and the fluid pressure trapped
pressure.
between the valves is released back to
the reservoir. The output and return
( 5 ) A high and low pressure filter
The
i s provided to remove any solid contami-
h o s e s ar e e a c h 3 0 f e e t i n l e n g t h .
n a t i o n in the hydraulic fluid. A switch
o u t p u t hose is 1/2 inch in diameter and
t h e return hose is 3/4 inch. Q u i c k d i s -
is connected across each filter. If the
f i l t e r gets dirty and the difference be-
connects containing check valves on each
tween input and output fluid pressure
end hold the fluid in the hose so it
Pro-
exceeds 50 psi the switch closes. As
w i l l not drain out between uses.
s h o w n on figure FO-9, closure of either
t e c t i v e caps are attached to keep quick
p r e s s u r e switch PS1 or PS2 causes the
d i s c o n n e c t fittings clean when hoses are
R E P L A C E FILTER light to illuminate.
not in use.
(8) The dual manifold is provided
( 6 ) The accumulator, figure FO-10,
b e c a u s e some aircraft require two hig h
s t o r e s hydraulic pressure to accommo-
p r e s s u r e and two r e t u r n connections.
The OUT-
d a t e brief changes in demand.
PUT PRESSURE gauge provides the opera-
This need is satisfied by dual connec-
tions on the manifold and the use of
t o r with an indication of pressure being
s h o r t ( 5 f o o t ) a d a p t e r h o s e s . The dual
a p p l i e d . The HIGH PRESSURE BYPASS valve
manifold provides additional fill and
provides a path for circulation of hy-
8-5
