(3)
You can also fill the oil reservoir with a pressure fill device through the pressure fill port. The oil which is more than the FULL mark limit flows through the overflow port back to the reservoir of the fill device.
(4)
The oil reservoir has a connection to the ambient air through an air/oil separator. The gear driven air/oil separator is connected through a gearbox vent line to the APU exhaust cone.
(5)
The oil drain plug is installed at the lowest point of the integral oil reservoir. The magnetic chip detector is installed in the drain plug. You can remove the drain plug with the chip detector installed. You can also remove the chip detector without the drain plug. The drain plug has a check valve which closes when you remove the chip detector. Thus it is not necessary to drain the oil reservoir for a visual check of the chip detector.
APU Oil System - Schematic
Figure 002
CES B. Distribution
(1)
The subsequent components make the oil distribution system:
-
a combined pressure and scavenge pump,
-
a generator scavenge pump,
-two oil filters,
-an oil cooler,
-a de-oil solenoid.
(2)
Oil Pumps The oil pump assembly is installed on a pad on the accessory drive gearbox (Ref. 49-26-00). The gearbox drives the central pump shaft of the oil pump and thus it supplies the mechanical power for its operation. The central pump shaft transmits also the mechanical power which is necessary to operate the Fuel Control Unit (FCU). The oil pressure pump removes the oil from the oil reservoir by suction. It supplies the lubrication oil to the oil cooler and the pressure oil filter. It regulates the oil pressure and supplies the temperature regulated and filtered oil to the lubrication points of:
-
the engine,
-
the load compressor,
-
the accessory drive gearbox,
-
the starter clutch,
-
the APU generator 8XS.
It removes the oil by suction (the scavenged oil) from:
-
the generator sump,
-
the turbine sump,
-
the APU generator.
The scavenged oil from the generator sump and the turbine sump is
returned to the oil reservoir with two scavenge pumps.
The generator scavenge oil is filtered from the generator scavenge
oil-filter and then supplied to the oil reservoir. This makes sure
that no contaminated oil returns from the generator to the oil
reservoir.
The oil which lubricates the gears, the starter clutch and bearings
of the gearbox, is returned to the reservoir by gravity.
(3)
Oil Cooler The oil cooler decreases the temperature of the oil. It is an oil/air heat exchanger which receives the cooling air from the cooling fan (Ref. 49-52-00). The oil cooler keeps the oil temperature within the limit during all operation conditions. A thermal bypass valve is installed at the oil cooler inlet. It makes sure that no oil with a temperature below 60 deg.C (140.00 deg.F) flows through the heat exchanger. This helps to increase the oil temperature quickly and keeps it high enough to prevent moisture intrusion. The valve is also an oil cooler bypass valve. When the oil cooler is blocked, the oil flows directly to the lubrication oil filter.
(4)
Filters The distribution system has two oil filters:
-
the pressure oil filter,
-
the generator scavenge oil-filter. The filters remove unwanted materials from the oil. The pressure oil filter cleans all the lubrication oil before it is supplied to the lubrication points. The generator scavenge oil-filter cleans unwanted materials from the generator scavenge oil. This makes sure that the generator does not give contamination to the oil in the oil reservoir. Each oil filter has a filter bypass valve which opens when the filter element is fully clogged. Then the oil does not flow through the filter element, but the APU receives lubrication oil. Differential pressure indicators on the filter housings are latched out if the filter element is clogged. You can set the differential pressure indicator again manually. Each oil filter has a delta pressure switch which signals the ECB when the filter element is fully clogged. Then the ECB initiates an APU shutdown when the aircraft is on the ground.
(5)
De-oiling Solenoid Valve The de-oiling solenoid valve reduces the oil pressure pump load during the APU start, especially during the cold start condition when oil has a high viscosity. The valve is located on the upper right hand side of the gearbox. A solenoid operates the valve position. The ECB controls the solenoid in relation to the de-oiling solenoid logic (Ref. 49-61-00). The solenoid valve is open when:
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