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The engine remains in computer-on control and
engine operation is not affected. See reset pro-
cedure under “L R ENG CMPTR FAULT” in
the
AFM
/Checklist.
If electrical power to the computer fails (i.e.
essential bus failure or CMPTR circuit breaker
opens and will not reset), the manual mode
solenoid valve is depowered open, engine con-
trol reverts to manual, and a white “MAN” EI
will appear in the corresponding N1 indication
on the EICAS.
If a fault occurs in the DEEC, it may remain
in the auto mode or it may revert to manual
mode depending on the fault. In either case,
an amber “L or R ENG CMPTR FAULT” mes-
sage will be posted on the CAS and if the en-
gine reverts to manual, an amber “MAN” will
annunciate within the corresponding N1 arc
(Figure 7-8). If the engine control transitions
to the manual mode, engine rpm may increase
or decrease somewhat depending on thrust
lever position, altitude, manual mode adjust-
ment and several other factors.
When engine control automatically reverts to
manual mode, it will not go back to computer-
on mode even if the fault clears, until the pilot
cycles the ENG CMPTR switch to OFF and
back to ON. If the pilot cycles the switch and
the ENG CMPTR FAULT message remains
illuminated, the fault conditions still exist.
Whenever engine control is in the manual mode
of operation a “MAN” annunciator will appear
inside of the analog N1 indicator on the EICAS
(Figure 7-8). If engine control has reverted to
manual due to a DEEC fault or failure, “MAN”
will be amber. If the pilot has switched the
computer switch to MAN or OFF the “MAN”
displayed on the EICAS will be white.
In the manual mode, engine response will be
noticeably slower and the surge bleed valve
goes to
1
/
3
open and stays there. This will re-
sult in reduced engine efficiency. Temperature
limiting and precise engine speed control is
lost except the mechanical governor in the
fuel controller should limit N
2
to 105% and,
if MAN is selected on the ENG CMPTR
switch, the ultimate overspeed protection will
still be available depending on the malfunc-
tion. Power adjustments should be made slowly
and cautiously, and much closer engine mon-
itoring is necessary in the manual mode.
ENGINE FUEL SYSTEM
GENERAL
The engine fuel system pressurizes fuel routed
to the engine from the airplane fuel system, fil-
ters and heats the fuel, regulates fuel flow and
delivers atomized fuel to the combustion sec-
tion of the engine. The system also supplies
high-pressure motive flow fuel to the airplane
fuel system for jet pump operation.
The major components in the engine fuel sup-
ply system are the engine-driven fuel pump
with an integral fuel filter, the fuel heater, the
fuel control unit (FCU), the flow divider and
the fuel manifolds (Figure 7-15).
ENGINE FUEL SUPPLY
Fuel is supplied to each engine-driven fuel
pump from the respective wing tank. This fuel
is normally supplied under pressure from the
standby pump or the jet pump in the wing tank.
During engine start the standby pump is au-
tomatically energized to provide fuel pres-
sure to the engine driven pump. After start, the
standby pump is automatically depowered and
the jet pump provides fuel pressure.
If the jet pump fails during engine operation,
low pressure is sensed in the engine supply line
and the CAS will generate a red “L/R FUEL
PRESS LOW” warning message. The AFM
procedure is to turn on the corresponding
standby pump for this indication. If the
standby pump is not turned on or is unavail-
able for some reason, the engine-driven fuel
pump can draw fuel directly from the wing tank
un-assisted, but with some limitations.
L E A R J E T 4 5
P I L O T T R A I N I N G M A N U A L
7-20
FOR TRAINING PURPOSES ONLY
FlightSafety
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