Hawker 800 XP, Pilot Training Manual

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7-10
FOR TRAINING PURPOSES ONLY
HAWKER 800 XP PILOT TRAINING MANUAL
FlightSafety
international
FUEL CONTROL
INTRODUCTION
The engine fuel control system consists of:
• Fuel Pump Assembly
• Hydromechanical Fuel Control Unit
(FCU)
• D i g i t a l E l e c t r o n i c E n g i n e C o n t r o l
(DEEC)
• Fuel Flow Divider Assembly
• Fuel Atomizers.
From the aircraft fuel system, the fuel con-
trol system pumps, filters, meters and atom-
izes the fuel before the ignition system ignites
it to produce thrust.
FUEL PUMP
An engine-driven fuel pump on the rear of the
accessory gearbox provides high pressure
fuel to the fuel control system. The pump as-
sembly consists of:
• Booster Pump Element
• Fuel Filter
• Filter Bypass Valve
• High Pressure Pump Element
• Relief Valve.
Attached to the rear of the pump is the fuel
control unit. See Figure 7-8.
Anti-ice Valve
An anti-icing valve is provided within the
fuel pump assembly to mix warm fuel from
the fuel heater with the discharge flow of the
booster pump to prevent icing of the fuel fil-
ter element.
Filter Bypass
The filter bypass valve allows fuel to bypass
the filter if an excessive pressure drop across
the filter occurs.
An electrical pressure switch will cause the
respective annunciator ENG # FUEL to be-
come lit when an excessive differential pres-
sure condition exists before bypassing occurs
or excessive fuel temperature.
Filter Clogged
If the filter starts to become clogged, the fol-
lowing events occur:
• At 6 to 8 psi
∆
p the amber annunciator
will be lit on the MWS.
• At 9 to 12 psi
∆
p the filter bypass valve
opens to deliver fuel to the high pres-
sure pump.
The annunciator will remain lit for as long as
the fuel filter remains clogged.
FUEL CONTROL UNIT
The fuel pump-driven fuel control unit (FCU)
on the rear of the fuel pump contains:
• Fuel Metering Section
• Power Lever Input Pot
• Shutoff Valve
• Outlet Pressurizing Valve
• Ultimate Overspeed Solenoid
• Mechanical Governor (N
2
)
The mechanical governor functions in two
modes: as an overspeed governor for the HP
rotor if the fuel computer is operative; or, as
a hydromechanical control when the fuel
computer is inoperative.