Page 2-18
Pilot’s Operating Manual
Revision A1: Nov, 2002
Sub-section 2
ENGINES
Hawker 800XP Pro Line 21
Section III - SYSTEMS DESCRIPTION
Oil Filter
A filter is provided to remove impurities from the oil. The oil filter consists of a disposable element
enclosed in a metal housing on the right side of the accessory drive gearbox.
Engine protection against filter clogging is provided by an oil filter bypass indicator valve located
adjacent to the oil filter. The valve opens when the pressure drop across the filter is excessive to bypass
lubricating oil around the filter.
An integral differential
∆
P pressure indicator on the valve visually flags a clogged filter condition before
bypassing occurs. A thermal lockout device on the
∆
P indicator prevents actuation under cold oil
conditions although the bypass valve will bypass oil under these conditions.
Oil Tank
A 1.65 US gallon capacity oil reservoir is located on the right side of the engine fan bypass housing.
The reservoir has a liquid level sight gauge and a filler cap on the right side of the tank. A filler tube and
cap are located on the left side of the tank which allows for oil tank replenishing when access to the right
side is restricted. Viewing ports are provided on the right side of the engine. (Figure 4)
Fuel Heater
An externally mounted fuel heater is located on the left side of the engine. The fuel heater provides oil-
to-fuel heat exchanging to prevent ice formation in the fuel system from clogging the fuel filter and any
other components.
Fuel flow through the fuel heater is thermostatically controlled to provide the optimum operating
temperature. Excess oil pressure with cold oil is prevented by a pressure bypass valve.
Air/Oil Cooler
After oil leaves the fuel heater, it passes through the air/oil coolers in the engine bypass duct. The air/
oil cooler consists of three segments: one half segment and two quarter segments.
Each segment is a finned unit with oil lines running through it. Together the three segments form the
inner surface of the fan duct.
A temperature controlled integral bypass valve directs oil that is hotter than 65
°
C through the three
segments of the air/oil cooler. Air flowing through the duct cools the oil that passes through the cooler.
Below this temperature, the valves bypass the oil around the air/oil cooler.
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 gearbox. The remaining oil flows
through the oil temperature regulator (fuel/oil cooler) and then on to the planetary gear assembly.
