Page 2-7
Pilot’s Operating Manual
Revision A1: Nov, 2002
Sub-section 2
ENGINES
Hawker 800XP Pro Line 21
Section III - SYSTEMS DESCRIPTION
Low Pressure Spool N
1
The LP N
1
spool consists of a four stage, low pressure, axial flow compressor and a three stage, low
pressure turbine. Both the compressor and the turbines are mounted on a common shaft.
NOTE: A stage is one rotor (rotating blades) and one stator (non rotating vanes).
Each stage of the axial flow compressor utilizes rotating compressor blades to accelerate the air,
followed by static stator vanes which decelerate the air, converting kinetic energy into pressure. This
provides a steady rise in pressure through the compressor stages, without significant change to overall
velocity.
High Pressure Spool N
2
The high pressure spool N
2
consists of a single stage centrifugal compressor driven by a single stage
turbine through an outer concentric shaft. The centrifugal compressor consists of an impeller (rotor), a
diffuser and a compressor manifold.
As in axial flow compressors, air is picked up and accelerated outwards towards the diffuser. When the
accelerating air reaches the diffuser its velocity is reduced, converting kinetic energy into pressure. The
high pressure spool also drives the accessory gearbox through a tower shaft and transfer gear
reduction system.
COMBUSTION CHAMBER
The compressed air flows into a single reverse flow annular combustion chamber in the turbine section
where it is mixed with atomized fuel supplied by twelve duplex fuel nozzles. The twelve duplex fuel
nozzles consists of primary nozzles used for starting and secondary nozzles used in conjunction with
the primary nozzles for all other phases of engine operations.
The fuel-air mixture is ignited by the two igniter plugs located at the six and seven o’clock positions
within the combustion chamber. After the ignition cuts-out, combustion is self sustaining and the
combustion gases are then directed to the turbine by the transition liner. The hot gases pass through
both the high and low pressure turbines, driving both rotating compressor assemblies and then exiting
through the exhaust nozzles with the bypassed air.
TURBINE SECTION
The turbine section contains four (one high pressure, three low pressure) axial flow turbine wheels and
four stator assemblies. On leaving the turbine, the exhaust gases enter a mixer compound-thrust-nozzle
system, where they mix with the bypass air before discharging through a convergent-divergent nozzle.
The high pressure turbine rotor assembly is air cooled to allow an increased turbine inlet temperature.
ACCESSORY DRIVE
An accessory drive gearbox and transfer gearbox are driven from the high pressure N
2
spool. The
transfer gearbox is driven by a vertical shaft and in turn drives the accessory gearbox through a
horizontal gearshaft.
The accessory drive gearbox provides shaft power for airplane accessories (hydraulic pump, starter/
generator and alternator) which are mounted on the forward face of the accessory gearbox. The fuel
pump, fuel control unit and oil pump are all mounted on the rear face of the accessory gearbox.
