MD Helicopters CSP-900RMM-2, Техническое обслуживание и ремонт

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CSP − 900RMM − 2 MD Helicopters, Inc.
Rotorcraft Maintenance Manual
Page 3
Revision 14
28-00-00
3. Fuel Distribution Subsystem
The fuel distribution subsystem supplies fuel
to the engines. Fuel is supplied from the fuel
cell through supply lines located in the aft
bulkhead of the baggage compartment.
The fuel distribution subsystem consists of the
following components:
Fuel Booster Pumps - Pressurizes fuel for
engine operation.
Fuel Supply Lines - Routes pressurized fuel
from the fuel cell to the engines.
Shutoff Valves - Shuts off the fuel supply to
the engines.
Fuel Pressure Switch - Measures fuel
pressure and sends a signal to the IIDS.
Crossfeed Valve (900 CONFIG) - Allows
fuel flow from one booster pump to both
engines in case of a single booster pump
failure.
NOTE:
(900 CONFIG - PW207E) The cross­
feed system, boost pump outlet check
valves, crossfeed valves,
CROSS FEED
switch and system hoses are removed when
upgraded from PW206A to PW207E .
Fuel Transfer System (902 CONFIG) -
Transfers fuel to the opposite side of the fuel
cell longitudinal baffle whenever the booster
pumps are operating.
A. Fuel Booster Pumps
The helicopter is equipped with two sub­
merged, electrically driven booster pumps
bolted to the sump plate in the fuel cell. The
pumps provide pressurized fuel to the engines.
Each booster pump is a single stage centrifu­
gal pump driven by a 24 - 28 vdc, 4.5 ampere,
negative ground motor. Each booster pump is
composed of two major components; the pump
housing assembly and the pump cartridge
assembly. The pump cartridge assembly
houses the dc motor and impeller. The pump
cartridge assembly is replaceable and can be
removed from the helicopter without defueling.
Pump Cartridge Assembly - The pump
cartridge assembly is a radial type impeller
which separates expanding vapors from the
fuel supply. Two bleed holes located in the
canister cover are covered by an umbrella
check valve. The umbrella valve permits fuel
vapors in the pump cartridge assembly to
escape, avoiding impeller cavitation. The
canister cover umbrella check valve also
prevents fuel leakage when the cartridge
assembly is removed.
The impeller is driven directly by the dc motor
shaft. The bearings in the dc motor are
hydrodynamically lubricated. Once shaft
rotation begins, there is no contact between
the shaft and the bearings.
Three bleed holes are located in an adapter
plug on top of the pump housing assembly
near the fuel inlet screen. The bleed holes are
covered by an umbrella check valve. The
umbrella check valve allows fuel vapors
entering the pump housing assembly to
escape.
A shutoff valve in the pump housing assembly
is manually closed during removal of the pump
cartridge assembly. The shutoff valve controls
fuel flow through the housing to the pump
cartridge assembly.
(900 CONFIG - PW206A) - A replaceable
fuel supply in-line check valve is located in the
fuel supply outlet of each booster pump
housing assembly. The check valve prevents
fuel from back flowing through a failed booster
pump.
Each booster pump is explosion proof. If fuel
vapors in the DC motor ignite, the flame is
quenched as it tries to pass through the fuel
passages in the pump housing assembly.
The booster pump fuel delivery volume at sea
level is 850 lbs/hr, nominal at 13.4 psi,
minimum at 75
°
F. Delivery at 20,000 feet is
400 lbs/hr, nominal at 6.5 psi, minimum at
110
°
F. The booster pumps are controlled by
individual switches on the center console.
B. Fuel Supply Lines
Self-sealing break-away frangible valve
connections and fittings prevent loss of fuel
from the fuel lines and fuel cell in the event of
a hard landing.
The frangible valve connectors are located in
the fuel lines that exit the fuel cell. Frangible
valves are also located in the fuel fittings
mounted on main transmission deck.