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The engine fuel valve, fuel metering valve, and spar valve allow fuel flow to the
engine when all valves are open. The valves open when the Engine Fire switch is
in and the Fuel Control switch is in RUN, and the engine pumps are supplying fuel
pressure. The pumps supply pressure when the N2 rotor is turning. During
autostart, the fuel metering valve is additionally controlled by the EEC. The
engine fuel valve, fuel metering valve, and spar valve close when either the Fuel
Control switch is in CUTOFF or the Engine Fire switch is out.
Fuel flow is measured downstream of the engine fuel valve and displays on the
secondary engine display. Fuel flow information is also provided to the FMS.
October 1, 2000
747 Operations Manual
Engines, APU -
Engine System Description
Copyright © The Boeing Company. See title page for details.
D6-30151-425 7.20.11
Engine Fuel System Schematic
ENG 3 FUEL VLV
ENG 3 FUELFILT
AUTOSTART
ON
CONTROL
ENGINE
ELECTRONIC
CUTOFF
RUN
3
FUEL CONTROL
FUEL
MEASURING
FIRST
FUEL
UNIT
SECOND
STAGE
FUEL
FILTER
FUEL/OIL
HEAT
EXCHANGER
METERING
OIL
B
STAGE
ENGINE
FUEL
VALVE
SPAR
VALVE
FF 20
FMS FUEL
FUNCTION
October 1, 2000
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
7.20.12 D6-30151-425
Engines, APU -
Engine System Description
Engine Oil System
The oil system cools and lubricates engine bearings and the accessory gearbox.
Oil is pressurized by an oil pump. The oil cools and lubricates the engine. The
scavenge pump scavenges oil from the engine. The oil is cooled by fuel as it flows
through the fuel/oil heat exchanger. An oil filter removes contaminants. If the filter
becomes saturated with contaminants, oil bypasses the filter. Oil then returns to
the oil reservoir.
Oil pressure, temperature, and quantity display on the secondary engine display.
Oil pressure is measured upstream of the engine. Oil temperature is measured
downstream of the engine.
During cruise, oil quantity displays on EICAS whenever oil quantity on one
engine differs from any other engine by a predetermined amount. When this
occurs, the lowest oil quantity is shown in magenta. If there is an increase in oil
quantity during cruise (indicator malfunction or leaking fuel/oil heat exchanger),
the EICAS oil partial engine indications display may appear. However, for this
condition the low quantity displays in magenta, even though that oil quantity may
be normal.
October 1, 2000
747 Operations Manual
Engines, APU -
Engine System Description
Copyright © The Boeing Company. See title page for details.
D6-30151-425 7.20.13
Engine Oil System Schematic
FUEL/OIL
G G G
2 2
98 1
1 1
P
T
OIL Q
OIL
OIL
FUEL
PUMP
S
TEMP
PRES
EN 4 OIL
EN 4 OIL
EN 4OIL FILT
P
P
Q
T
EXCHANGER
HEAT
B
OIL
PUMP
SCAVENGE
FILTER
OIL
BEARINGS
GEAR BOX
86 10
60
October 1, 2000
747 Operations Manual
Copyright © The Boeing Company. See title page for details.
7.20.14 D6-30151-425
Engines, APU -
Engine System Description
Thrust Reverser System
Each engine has a pneumatically actuated fan air thrust reverser. Each thrust
reverser is powered by bleed air from the related engine. The reverser does not
operate if the engine is not running. Reverse thrust is available only on the ground.
An interlock mechanism in the Thrust lever assembly prevents simultaneous
movement of the Forward and Reverse Thrust levers. The Reverse Thrust levers
can be raised only when the Forward Thrust levers are in the closed position.
When the Reverse levers are down, the reversers are locked in the stowed position.
Raising the Reverse Thrust levers to the idle detent locks the Forward Thrust
levers in position. Bleed air unlocks and extends the reversers aft to the deployed
position. A thrust reverser status annunciator displays above the digital indicator
of each N1 indication. The annunciator displays in amber when the related
reverser is unlocked or moving. The annunciation changes color to green when the
reverser is fully deployed. The interlock releases and the Reverse Thrust levers can
bemoved to full reverse,.
Pushing the Reverse Thrust levers to the full down position retracts the reversers
to the stowed and locked position. The REV indication changes color back to
　
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