15.10 - Lubrication Systems Flashcards
Describe the main difference between a ‘wet sump’ and a ‘dry sump’?
A ‘wet sump’ system has it’s oil supply carried in an integral wet sump i.e the reservoir is located centrally at the base of the engine. An example of a wet sump system is the APU.
A ‘dry sump’ system has it’s oil supply carried in a separate tank and features a scavenge system to return the oil to this tank. Used on all basic types of aviation gas turbine engines
What is the primary purpose of a lubricant?
The primary purpose of a lubricant is to reduce friction between moving parts.
As long as this oil film remains unbroken, metallic friction is replaced by internal fluid friction. The heated oil is then carried away to be cooled and reused.
Describe how a gear pump operates
This type of pump has a drive gear and a driven gear. Both the gears nn close-tolerance housing carry oil from the inlet port between them and to squeezing the oil out the outlet. This is the most common form of aero-engine oil pump.
How is the ‘clogging’ of a filter indicated?
Indicators can vary from a simple ‘’pop-out’’ button on the filter housing to indicate clogging. Another method to indicate clogging of a filter is a pressure differential sensor across the filter which is capable of triggering a flight deck warning master caution or simple warning light.
Explain briefly the difference between a ‘cold tank’ and ‘hot tank’ lubrication system.
A ‘cold tank’ lubrication system contains the oil cooler in the combined scavenge return to the oil tank.
A ‘hot tank’ lubrication system contains the oil cooler in the pressure oil delivery side.
What is used to detect the presence of ferrous debris in a scavenge return:
Magnetic chip detectors in the form of removable plugs are installed in each individual scavenge pump. Their purpose is to assist in the condition monitoring of the engine at large by collecting ferrous debris from particular parts of that engine. Thus providing early warning of impending failure.
What is the difference between a ‘‘Hot tank’’ system and ‘‘Cold tank’’ system in terms of oil cooler?
Hot tank = oil cooler in pressure line, after pressure pump
Cold tank = Scavenge return line
List the three subsystems of the lubrication system in a gas turbine engine
- Supply/Pressure
- Scavenge,
- Vent systems
Differentiate between a wet sump system and a dry sump system
(also where are they used?)
Wet sump System = Oil supply is carried in an integral wet sump. A reservoir is usually located centrally at the base of the engine. APU’s
Dry sump System = The oil reservoir is a separate tank, usually mounted low on one side of the engine’s compressor or fan casing
All modern aviation gas turbine engines
Why have scavenge pumps got a larger capacity than a pressure pump?
Scavenge pumps return used oil to the reservoir and air/mist is present in the returning oil.
It is approx 150% the capacity of pressure pumps
List the 3 common types of oil pumps?
- The vane pump
- The Gear pump
- The Gerotor pump
What way does oil in a filter flow?
They are usually constructed so as to
filter ‘‘out-to-in’‘
Where are the magnetic chip detectors normally located?
Normally installed before the inlet to each individual scavenge pump
Also found in the oil tank or accessory gearbox
(Note diagram shows a ‘dry’ sump system)
List the various types of filter used on an engine?
Depends on location but:
- Pressure filter
- Scavenge filter
- Last-chance filter
- Tank strainer
How can a filter bypass be indicated?
Indicators cab vary from a simple ‘‘pop-out’’ (clogging indicator) button on the filter housing to a pressure differential sensor across the filter capable of triggering a flight deck warning.
Usually modern filters incorporate both
Is the following a cold or hot tank system and is it a wet or dry sump system?
Hot tank system as oil cooler is in pressure delivery line
Wet sump system as oil reservoir is part of the engine
Is the following a cold or hot tank system and is it a wet or dry sump system?
Cold tank system as oil cooler is located in the scavenge return line
Dry sump system as the oil tank/reservoir is located outside the engine i.e oil reservoir is a separate tank
What is the purpose of a vent system?
Ensures proper flow to bearings
And keeps positive pressure on oil in tank flowing to pressure pump to prevent pump cavitation
