Hawker 800 XP, Pilot Training Manual

Page: 232 / 504

If the heat exchangers become obstructed, the
temperature control valve bypasses the oil
around them.
After the oil leaves the air/oil coolers, the
flow splits. Part of the oil flows to the engine
bearing sumps (HP rotor shaft), the transfer
gearbox assembly and the accessory gear-
box. The remaining oil flows through the oil
temperature regulator (fuel/oil cooler) and
then on to the planetary gear assembly.
Fuel/Oil Cooler
The fuel/oil cooler (oil temperature regulator)
uses aircraft fuel to maintain the oil at a con-
stant temperature.
The unit consists of a temperature control
valve and a heat exchanger. Whatever the oil
temperature, fuel constantly flows through
the unit: oil only flows through the unit if it
is above a set temperature. If the oil temper-
ature exceeds 99° C, the control valves open
to rout the oil through the cooler.
From the fuel/oil cooler, oil then lubricates the
fan shaft bearings and the front LP spool bear-
ings. After travelling to all the main sump
areas, oil then drains by gravity to the lowest
point of each sump. The scavenge pumps then
draw the oil back to the engine oil reservoir.
Oil Venting
Vent lines interconnect the oil sumps to the oil
tank assembly and the breather pressurizing
valve. The breather pressurizing valve pro-
vides an ambient vent for the oil system at
low altitudes and at high altitude increases
the internal engine vent and tank pressure to
ensure proper oil pump operation.
Oil Pressure and Temperature
Indications
Indicators scaled from 0 to 70 psi display the
oil pressure for each engine. A pressure trans-
mitter in the oil supply manifold for each en-
g i n e ’s p l a n e t a r y g e a r a s s e m b l y s u p p l i e s
electrical signals to the two oil pressure indi-
cators on the center instrument panel.
Temperature bulbs in each engine’s oil supply
manifold are connected electrically to two oil
temperature indicators on the center instrument
panel. Each indicator has a single pointer that
moves over a scale marked from 0° C to 170°
C increments (see Figure 7-6).
7-8
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HAWKER 800 XP PILOT TRAINING MANUAL
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Figure 7-6. Center Instrument Panel