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HP RPM Ranges (%)
Oil Pressure (PSIG)
White Indication Red Indication
< 76.0 > 16 < 15
78.4 ≥ HP > 76.0 > 17 < 16
80.0 ≥ HP > 78.4 > 18 < 17
> 80 > 30 < 29
(2) The engine oil pressure parameters (air mode) are as follows:
• Air Operation = Greater Than Four Minutes Following WOW
Transition
HP RPM Ranges (%)
Oil Pressure (PSIG)
White Indication Red Indication
< 76.0 > 16 < 15
78.4 ≥ HP > 76.0 > 17 < 16
80.8 ≥ HP > 78.4 > 18 < 17
83.2 ≥ HP > 80.8 > 19 < 18
85.6 ≥ HP > 83.2 > 20 < 19
88.0 ≥ HP > 85.6 > 21 < 20
90.4 ≥ HP > 88.0 > 22 < 21
92.8 ≥ HP > 90.4 > 23 < 22
95.2 ≥ HP > 92.8 > 24 < 23
> 95.2 > 25 < 24
OPERATING MANUAL
2A-79-00 PRODUCTION AIRCRAFT SYSTEMS
Page 2
May 31/01
Revision 4
C. Low Oil Pressure Switch:
(See Figure 2.)
The low oil pressure switch is a 15 ±0.4 PSI switch that activates the low oil
pressure warning system if the pressure falls below its set parameter.
When the oil pressure is less than the lowest acceptable limit, the contacts
stay closed. This causes the low pressure warning indicator in the crew
compartment to illuminate. Oil fills the diaphragm chamber through holes in
the circular base plate of the switch assembly. As the pressure increases,
the diaphragm causes a pushrod to move to the moving contact. When the
pressure is more than the setting limit the contacts open and the warning
indicator in the crew compartment extinguishes.
The electrical contacts attach to the bottom of the terminal block. A setting
adjustment assembly is attached to the terminal block molding. This
assembly permits the contacts to operate at any specified oil pressure
within the setting range.
The top cover assembly contains a flame trap. This flame trap will stop the
spread of fire if the contacts arc when oil vapor is in the switch.
D. Oil Pump Assembly:
(See Figure 4.)
The oil pump unit, driven by the right gearbox, consists of six internal oil
pumps, consisting of one oil pressure pump and five oil scavenge pumps.
These internal pumps affect the following components:
• LP Turbine Bearing
• Internal Gearbox
• Thrust Bearings
• HP Turbine Bearing
• Right Gearbox
(1) Oil Pressure Pump:
The oil pressure pump supplies pressurized engine oil to the
components (listed above). The pump is a gear-driven positivedisplacement
pump and incorporates a 200 PSI pump pressure
relief valve. If the pump output exceeds 200 PSI, the excess
pressure is returned back to the pump inlet.
(2) Oil Scavenge Pumps:
The oil scavenge pumps return engine oil from the engine
components (listed above) back to the oil tank. The return oil output
from four of the pumps (all except the right gearbox return oil) is
directed into a common oil return tube to the tank.
The right scavenge pump return oil is pumped through a separate
tube to prevent oil from siphoning from the oil tank to the right
gearbox when the engine is not operating.
E. Oil Filter Assembly:
(See Figure 2.)
The oil filter assembly mounts on the front wall of the engine oil tank. The
oil flows from the oil cooler into the filter housing, flowing from the outside
to the inside of the element. If the pressure difference across the element is
OPERATING MANUAL
PRODUCTION AIRCRAFT SYSTEMS 2A-79-00
Page 3
May 31/01
Revision 4
more than 50 PSI, the bypass valve opens to let the oil bypass the element.
The system relief valve is subjected to the pressure downstream of the
element. If this pressure is more than 50 PSI, the valve opens to allow the
oil flow back into the tank below the de-aerator tray.
An oil filter differential pressure indicator assembly (mounted on the rear
wall of the oil tank) will indicate if there is a blockage in the pressure oil
filter. When the differential pressure across the filter is more than 18 ±3.0
PSID, the indicator button compression spring forces a red button to
extend (approximately 0.187 inch) from the body of the indicator. When the
differential pressure exceeds 30 ±4.5 PSID, the differential pressure switch
closes, which illuminates a blue L-R OIL FILT BPASS message on the
EICAS.
After passing through the element, the oil is directed through two tube
connectors. One tube conveys oil to a two-way connector on the bypass
duct, from where the oil passes to the turbine bearings and central feed oil
tube. The other tube moves oil to the high-speed gearbox.
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湾流4操作手册 Gulfstream IV Operating Manual 3(16)
