Revision 1
7-14
FOR TRAINING PURPOSES ONLY
HAWKER 800 XP
PILOT TRAINING MANUAL
FlightSafety
international
If the electronic engine control malfunctions,
the FCU on the engine automatically switches
to the manual mode and the respective ENG
CMPTR annunciator will become lit.
Surge Bleed Valve
Under certain conditions, gas turbine engines
tend to surge and stall. For each compressor
rpm, there is a relationship between the amount
of air flow and the pressure gradient; a dis-
turbance results in the engine surging. A surge
bleed valve protects against this problem.
The DEEC controls the position of the surge
bleed valve which is located between the LP
compressor and the HP compressor, to prevent
compressor stalls and surges. If the valve
opens, compressed air flows into the bypass
duct smoothing out the pressure gradient
throughout the engine.
The DEEC normally positions the surge bleed
valve fully open for start and idle conditions
and fully closed for high rpm conditions. For
transient rpm conditions, however, the DEEC
modulates the surge bleed valve in response
to impending stall conditions. With the DEEC
off or failed, the surge bleed valve remains
1/3 open.
Fuel Flow Divider Assembly
The fuel flow divider is between the fuel con-
trol unit ant the fuel atomizers. During the en-
gine start, the divider routes fuel at a reduced
pressure to the primary atomizers. As the start
sequence continues and the rpm increases, the
fuel flow and pressure difference across the di-
vider orifice increases; fuel passes into the
secondary lines that supply the fuel atomizers.
Fuel Atomizers
Each engine uses twelve duplex (primary and
secondary) fuel atomizers on two manifold
assemblies; each manifold contains six du-
plex atomizers. Fuel swirls and breaks into mi-
croscopic droplets as it passes through the
atomizer orifice into the combustion chamber.
The primary and secondary fuel atomizers
provide a finely atomized fuel spray pattern.
Fuel Heating
The fuel heater permits oil-to-fuel heat ex-
change to maintain the desired temperature and
prevents ice formation in the fuel system from
clogging the fuel pump assembly fuel filter.
A portion of the engine fuel supply is diverted
through the fuel heater by the thermostati-
cally operated anti-ice valve located in the
fuel pump.
An amber ENG FUEL 1 or 2 annunciator will
become lit when the temperature of the fuel
in the associated fuel pump becomes exces-
sive or the fuel filter becomes clogged (see
Figure 7-11).
OVSPD PROT
ENG 1
FUEL
ENG 2
FUEL
Figure 7-11. Engine Fuel Annunciators
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