CSP−900RMM−2 MD Helicopters, Inc.
Rotorcraft Maintenance Manual
Page 4
Revision 14
28-00-00
When tensile, shear, or bending loads are
applied to the fuel supply line connectors and
fittings, the frangible valve section breaks,
allowing the two halves of the coupling to
separate and seal the fuel passages. Once the
frangible valve closure has occurred, a detent
moves into position and prevents the valve
from reopening. An indicator is visible around
the frangible connector when the valve is
closed.
The fuel supply lines from the fuel cell to the
main transmission deck are shrouded and
connected to a drain line to vent leaking fuel.
C. Fuel Pressure Switch
The fuel pressure switch is a diaphragm type
normally closed switch.
When measured fuel pressure is less than 3
psig, the switch closes sending a signal to the
IIDS display. The fuel flow bar indicator
segments illuminate when fuel pressure is 3
psig or less.
D. Fuel Shutoff / Crossfeed
Fuel Shutoff Valves - The engine fuel
shutoff valves are used to perform emergency
shut down of the engines. The fuel shutoff
valve is a 28 vdc, two position motor actuated
valve. The valve is normally open, and is
controlled by a pilot activated switch on the
fuel system control panel. The valve has 2
limit switches that stop the travel and 2
position indicator switches that complete an
electrical circuit to illuminate a valve position
light on the IIDS display. The fuel flow bar
indicator on the IIDS display illuminates
shutoff valve positions. Each engine shutoff
valve is shown in the open position when the
upper bar of each shutoff valve indicator
segment is not illuminated. The upper bar of
each indicator segment is illuminated when
the valve is closed.
The valve consists of an actuator and valve
body. The valve body consists of an aluminum
alloy body, aluminum alloy ball, support
fittings, thermal relief assembly, seals,
mounting bracket and associated hardware.
The actuator consists of an electric motor, gear
train, electrical magnetic interference (EMI)
filtering, limit switches, and electrical connec
tor. The limit switches are positioned near
each end of the actuator's rotational travel to
interrupt motor power and illuminate a valve
position indicator lamp on the IIDS display.
Fuel Crossfeed Valve (900 CONFIG -
PW206A) The fuel crossfeed/shutoff valve is a
28 vdc, two position motor actuated valve. The
valve is normally closed, and is controlled by a
pilot activated switch on the fuel system
control panel. The valve has 2 limit switches
that stop the travel and 2 position indicator
switches that complete an electrical circuit to
illuminate a valve position light on the IIDS
display. The valve allows both engines to be
fueled by the same or alternate booster pump.
In the event of a failed booster pump, the
crossfeed valve is opened allowing the operat
ing booster pump to supply fuel to both
engines. The valve consists of an actuator and
valve body. The valve body consists of an
aluminum alloy body, an aluminum alloy ball,
support fittings, thermal relief assembly, seals,
mounting bracket and associated hardware.
The actuator consists of an electric motor, gear
train, electrical magnetic interference (EMI)
filtering, limit switches, and electrical connec
tor. The limit switches are positioned near
each end of the actuator's rotational travel to
interrupt motor power and illuminate a valve
position indicator lamp on the IIDS display.
The fuel flow bar indicator on the IIDS display
illuminates crossfeed valve positions. The
crossfeed valve is shown in the open position
when the bar of the crossfeed indicator
segment is illuminated. Each of the valve
indicator segments will flash when the valve is
in between an open or closed position.
The fuel shutoff/crossfeed valves are shrouded
and connected to the shrouded fuel supply
lines to vent leaking fuel.
E. Fuel Transfer System (902 CONFIG)
The fuel transfer system is designed to
equalize the fuel in the left and right fuel
cavities and minimize unusable fuel.
When either electric booster pump is operat
ing, fuel is pumped through a jet pump in the
opposite fuel cell cavity. The jet pump draws
fuel from the sump through a pickup and the
fuel is ejected on the other side of the longitu
dinal baffle. For example, when the left
booster pump is operating, fuel is transferred
to the left fuel cell cavity.
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