15.10 Lubrication Systems Flashcards
What is the purpose of the lubrication system in gas turbine engines?
To distribute oil to the engine bearing compartments and gearboxes.
What are the two types of lubrication systems used in gas turbine engines?
- Wet sump lubrication systems
- Dry sump lubrication systems
How does a wet sump lubrication system differ from a dry sump lubrication system?
Wet sump systems store oil in the engine, while dry sump systems use an external supply tank.
What is a full-flow lubrication system?
The simplest type of oil supply system without a way to regulate oil pressure.
What factors influence oil pressure in a full-flow lubrication system?
- Rotor speed (N2)
- Oil temperature
- Flow areas downstream of the supply pump
What happens to oil pressure when N2 rotor speed increases?
Oil pressure increases due to higher flow of oil through the supply lines.
What is the effect of oil temperature on oil viscosity in a full-flow system?
An increase in oil temperature leads to lower viscosity, resulting in lower oil pressure.
What is a pressure relief valve used for in a lubrication system?
To prevent oil pressure from becoming too high.
What is a constant pressure lubrication system?
A system with a pressure-regulating valve that maintains oil pressure at a design value.
What are the advantages of a constant pressure lubrication system compared to a full-flow system?
- Maintains low oil pressure
- No increase in oil temperature after power reduction
What is a disadvantage of the constant pressure lubrication system?
It is more complex and requires adjustments during maintenance.
What components are generally found in most turbine lubrication systems?
- Oil reservoir and supply system
- Scavenge system
- Vent system
- Monitoring system
What is the primary purpose of the oil reservoir in a lubrication system?
To supply oil to lubricate, cool, and clean the engine bearings and gearboxes.
How is oil typically filled into the oil tank?
- Gravity fill
- Pressure fill
What is the function of a strainer in the oil tank?
To catch large foreign particles during servicing.
What is the primary source of oil cooling in a lubrication system?
The fuel-cooled oil cooler.
What are the two types of oil pumps commonly used in lubrication systems?
- Gear pump
- Gerotor pump
What is the main function of the oil pump in a lubrication system?
To supply oil under pressure to parts of the engine that require lubrication.
What is the purpose of an oil pressure regulating valve?
To keep the pressure within certain limits in the oil system.
What is the role of a bypass valve in an oil system?
To maintain proper oil temperature or pressure by varying the total oil flow passing through the cooler or filter.
What is the function of oil filters in a lubrication system?
To clean the oil and protect the system from contaminants.
What are the two main types of oil coolers used in turbine engines?
- Fuel-cooled oil coolers
- Air-cooled oil coolers
What is the difference between a hot tank system and a cold tank system?
- Hot tank system: oil is not cooled before returning to the oil tank
- Cold tank system: oil is cooled before returning to the oil tank
What components make up a typical fuel-cooled oil cooler?
- Housing
- Cover
- Core
What is the purpose of air-cooled oil coolers?
To remove excessive heat from the oil.
On which types of engines are air-cooled oil coolers typically used?
Turboprop engines and APUs.
Why are large air coolers necessary on turboprop engines?
Because the fuel flow is low relative to the heat to be removed from the oil and the quantity of oil is relatively high.
What are the main components of a typical fuel-cooled oil cooler?
- The housing
- The cover
- The core
What happens if the passage of oil through the core of a fuel-cooled oil cooler is clogged?
The oil flows through the oil bypass valve to the exit.
What is the function of the scavenge pumps in the oil pump and pressure filter housing?
To remove oil and contaminants from the bearing compartments and gearboxes.
How does the scavenge oil return to the engine oil tank?
Through the scavenge oil filter.
What does the scavenge oil filter differential pressure switch monitor?
The condition of the filter.
What is the role of the breather in the external gearbox?
To remove air from the scavenge oil.
What is the purpose of a de-aerator in the scavenge oil system?
To separate air from the incoming scavenge oil.
What does the pressurisation valve in the oil tank do?
Holds air pressure in the tank above a minimum level to prevent foam build-up.
True or False: The oil indication subsystem monitors only oil quantity.
False.
What types of oil quantity transmitters are commonly used?
- Capacitance-type transmitter
- Reed switch type transmitter
How does a capacitance-type transmitter measure oil level?
By the capacitance change of a capacitor formed by the probe and tank wall.
What does a reed-type transmitter use to determine the oil level?
A float with permanent magnets that activate reed switches.
What is the main concern regarding oil contamination?
The presence of metal particles that disrupt flow and lubricating properties.
What does the Spectrometric Oil Analysis Program (SOAP) monitor?
Internal wear of lubricated engine components by analyzing particles in the oil.
What size particles can SOAP detect that are not caught by oil filters?
Particles ranging from 0.001 mm to 0.02 mm.
What is the significance of identifying metals during spectrometric oil analysis?
Helps determine the source of contamination and areas for troubleshooting.
What do magnetic chip detectors do?
Catch metal particles that are attracted to magnets.
How can the condition of magnetic chip detectors be monitored?
Manually checked at fixed intervals or electronically monitored.
What happens if the resistance between the magnets of a chip detector falls below a limit?
The electronic control unit sends a maintenance message.
What is the procedure for checking oil quantity in aircraft engines?
At intervals specified in the maintenance schedule using sight gauges or ECAM/EICAS displays.
What is the purpose of the anti-siphon device in oil tanks?
To prevent siphoning of oil from the tank to the gearbox.
What should be done before opening the oil tank filler cap after engine shut-down?
Wait at least five minutes to prevent hot oil spray.
What should be done if fuel smell is detected when opening the oil tank filler cap?
Indicates a leakage in the fuel-cooled oil cooler and requires further troubleshooting.
Fill-in-the-blank: The oil servicing system uses _______ filling to replenish oil.
pressure
What is the recommended practice for using oil cans for refilling?
Minimize use for environmental reasons and use new, closed cans.
What is the danger of overfilling the oil tank?
Can pump a large amount of oil into the forward bearing compartment or de-oiler.
Why is it important to monitor oil consumption in the engine?
To keep track of the quantity of oil added to the tank.
