M15.10 Lubrication Systems Flashcards
What is the primary purpose of the lubrication system in gas turbine engines?
To distribute oil to the engine bearing compartments and the gearboxes.
What are the two types of lubrication systems used in gas turbine engines?
- Wet sump lubrication system
- Dry sump lubrication system
What is a wet sump engine lubricating system?
A system that stores the oil in the engine.
What does a dry sump engine lubricating system use?
An external supply tank mounted on the engine or near the engine.
How is oil re-circulated through the lubrication system?
By pumps that maintain a constant pressure.
What is a full-flow system in engine oil supply?
The simplest type of oil supply system with no way of regulating oil pressure.
What factors change the oil pressure in a full-flow system?
- Rotor speed (N2)
- Oil temperature
- Flow areas downstream of the supply pump
What happens to oil pressure when the N2 rotor speed decreases?
Oil pressure also decreases.
What is the effect of increasing oil temperature on oil viscosity?
It leads to lower viscosity of the oil.
What is a common consequence of external leakage in the oil system?
A decrease in oil pressure and oil quantity.
What is the role of a pressure relief valve in the lubrication system?
To prevent oil pressure from becoming too high.
What is a constant pressure system in engine oil supply?
A regulated pressure system that maintains oil pressure at a given design value.
True or False: In a constant pressure system, changes in oil temperature affect oil pressure.
False.
What are the advantages of the full-flow system?
- Simplicity
- No adjustments necessary during maintenance
What are the disadvantages of the full-flow system?
- Requires a large supply pump or high oil pressure at idle
- Significant rise in oil temperature after power reduction
What is the critical lubricating point in a turbine engine due to high temperatures?
The exhaust turbine bearing.
What is the function of air-cooling in turbine engines?
To cool the turbine components using bleed air from the compressor.
What are the four subsystems of a basic lubrication system?
- Oil reservoir and supply system
- Scavenge system
- Vent system
- Monitoring system
What is the purpose of the oil reservoir and supply system?
To supply oil to lubricate, cool, and clean the engine bearings and gearboxes.
What materials are typically used for the oil tank in a lubrication system?
Aluminium alloy coated with silicone for fire resistance.
What are the two methods for filling the oil tank?
- Gravity fill
- Pressure fill
What is the purpose of a strainer in the oil tank?
To catch large foreign particles during servicing.
Where does the oil flow after leaving the oil tank?
To the oil pump and pressure filter housing.
What is the primary source of oil cooling in the distribution system?
The fuel-cooled oil cooler.
What are the two most common types of oil pumps used in turbine engines?
- Gear pump
- Gerotor pump
What is the function of an oil pressure regulating valve?
To keep the pressure in the system within certain limits.
What is the purpose of a pressure relief valve in large turbofan oil systems?
To relieve pressure and bypass oil back to the inlet side of the oil pump.
What is the function of bypass valves in oil systems?
To maintain proper oil temperature or pressure by varying oil flow through the cooler or filter.
What is the role of oil filters in the lubrication system?
To clean the oil and protect the system.
What are the two main types of oil coolers used for turbine engines?
- Fuel-cooled oil coolers
- Air-cooled oil coolers
What does the term ‘scavenging’ refer to in the lubrication system?
Removing oil and contaminants from bearing compartments and gearboxes.
What system component removes air from the scavenge oil?
A breather in the external gearbox.
What types of transmitters are used in the oil indication subsystem?
- Capacitance-type transmitter
- Reed switch type transmitter
What is the principle behind the capacitance-type oil quantity transmitter?
Capacitance change of a capacitor.
What does the debris monitoring system in oil lubrication do?
Monitors the quantity, size, and type of particles in the oil.
What is the Spectrometric Oil Analysis Program (SOAP) used for?
To identify internal wear of lubricated engine components.
What is the size range of particles that SOAP can detect in oil?
From 0.001 mm to 0.02 mm.
What is the significance of monitoring metal particles in engine oil?
To identify increased wear for bearings and gears at an early stage.
What does spectrometric analysis for oil samples help identify?
Metal particles suspended in oil
Each metal produces a unique spectrum when vaporized, allowing for identification and quantification.
How are oil samples for SOAP taken?
From the oil tank at regular intervals
Samples are sent to a laboratory for analysis.
What is the purpose of the high-voltage AC spark in spectrometric oil analysis?
To burn the film of oil on the rotating disk
This allows light emitted to pass through slits for metal detection.
What metals are commonly analyzed in turbine engine oils?
- Aluminium
- Iron
- Chromium
- Silver
- Copper
- Tin
- Magnesium
- Lead
- Nickel
- Titanium
Each metal has a specific threshold limit of contamination measured in parts per million.
What is the threshold limit of contamination?
The maximum amount of normal wear for each metal
It is measured by weight in parts per million (PPM).
What do magnetic chip detectors do?
Catch metal particles attracted to the magnet
They provide a quick assessment of oil condition.
How can the condition of magnetic chip detectors be checked?
Manually at fixed intervals or electronically monitored
They can be removed when necessary.
What should be done before opening the oil tank filler cap after engine shut-down?
Wait at least five minutes
This prevents hot oil from spraying out.
What is the risk indicated by a fuel smell when opening the oil tank filler cap?
Leakage in the fuel-cooled oil cooler
Further troubleshooting is required if this smell is detected.
What are the two methods to replenish the oil system?
- Gravity filling
- Pressure filling
Gravity filling uses oil cans, while pressure filling uses an oil servicing system.
Why is it important to monitor engine oil consumption?
To ensure proper maintenance and record keeping
The quantity of oil added should be entered in the aircraft’s technical logbook.
True or False: The oil tank is usually located below the level of the gearbox.
False
The oil tank is located above the gearbox.
Fill in the blank: Spectrometric oil analysis provides invaluable information to help determine the source of _______.
Contamination
Engine manufacturers provide lists of engine components for troubleshooting.
