M15.10 Lubrication Systems

Question 1

What is the primary purpose of the lubrication system in gas turbine engines?

Answer 1

To distribute oil to the engine bearing compartments and the gearboxes.

Question 2

What are the two types of lubrication systems used in gas turbine engines?

Answer 2

• Wet sump lubrication system
• Dry sump lubrication system

Question 3

What is a wet sump engine lubricating system?

Answer 3

A system that stores the oil in the engine.

Question 4

What does a dry sump engine lubricating system use?

Answer 4

An external supply tank mounted on the engine or near the engine.

Question 5

How is oil re-circulated through the lubrication system?

Answer 5

By pumps that maintain a constant pressure.

Question 6

What is a full-flow system in engine oil supply?

Answer 6

The simplest type of oil supply system with no way of regulating oil pressure.

Question 7

What factors change the oil pressure in a full-flow system?

Answer 7

• Rotor speed (N2)
• Oil temperature
• Flow areas downstream of the supply pump

Question 8

What happens to oil pressure when the N2 rotor speed decreases?

Answer 8

Oil pressure also decreases.

Question 9

What is the effect of increasing oil temperature on oil viscosity?

Answer 9

It leads to lower viscosity of the oil.

Question 10

What is a common consequence of external leakage in the oil system?

Answer 10

A decrease in oil pressure and oil quantity.

Question 11

What is the role of a pressure relief valve in the lubrication system?

Answer 11

To prevent oil pressure from becoming too high.

Question 12

What is a constant pressure system in engine oil supply?

Answer 12

A regulated pressure system that maintains oil pressure at a given design value.

Question 13

True or False: In a constant pressure system, changes in oil temperature affect oil pressure.

Answer 13

False.

Question 14

What are the advantages of the full-flow system?

Answer 14

• Simplicity
• No adjustments necessary during maintenance

Question 15

What are the disadvantages of the full-flow system?

Answer 15

• Requires a large supply pump or high oil pressure at idle
• Significant rise in oil temperature after power reduction

Question 16

What is the critical lubricating point in a turbine engine due to high temperatures?

Answer 16

The exhaust turbine bearing.

Question 17

What is the function of air-cooling in turbine engines?

Answer 17

To cool the turbine components using bleed air from the compressor.

Question 18

What are the four subsystems of a basic lubrication system?

Answer 18

• Oil reservoir and supply system
• Scavenge system
• Vent system
• Monitoring system

Question 19

What is the purpose of the oil reservoir and supply system?

Answer 19

To supply oil to lubricate, cool, and clean the engine bearings and gearboxes.

Question 20

What materials are typically used for the oil tank in a lubrication system?

Answer 20

Aluminium alloy coated with silicone for fire resistance.

Question 21

What are the two methods for filling the oil tank?

Answer 21

• Gravity fill
• Pressure fill

Question 22

What is the purpose of a strainer in the oil tank?

Answer 22

To catch large foreign particles during servicing.

Question 23

Where does the oil flow after leaving the oil tank?

Answer 23

To the oil pump and pressure filter housing.

Question 24

What is the primary source of oil cooling in the distribution system?

Answer 24

The fuel-cooled oil cooler.

Question 25

What are the two most common types of oil pumps used in turbine engines?

Answer 25

* Gear pump * Gerotor pump

Question 26

What is the function of an oil pressure regulating valve?

Answer 26

To keep the pressure in the system within certain limits.

Question 27

What is the purpose of a pressure relief valve in large turbofan oil systems?

Answer 27

To relieve pressure and bypass oil back to the inlet side of the oil pump.

Question 28

What is the function of bypass valves in oil systems?

Answer 28

To maintain proper oil temperature or pressure by varying oil flow through the cooler or filter.

Question 29

What is the role of oil filters in the lubrication system?

Answer 29

To clean the oil and protect the system.

Question 30

What are the two main types of oil coolers used for turbine engines?

Answer 30

* Fuel-cooled oil coolers * Air-cooled oil coolers

Question 31

What does the term 'scavenging' refer to in the lubrication system?

Answer 31

Removing oil and contaminants from bearing compartments and gearboxes.

Question 32

What system component removes air from the scavenge oil?

Answer 32

A breather in the external gearbox.

Question 33

What types of transmitters are used in the oil indication subsystem?

Answer 33

* Capacitance-type transmitter * Reed switch type transmitter

Question 34

What is the principle behind the capacitance-type oil quantity transmitter?

Answer 34

Capacitance change of a capacitor.

Question 35

What does the debris monitoring system in oil lubrication do?

Answer 35

Monitors the quantity, size, and type of particles in the oil.

Question 36

What is the Spectrometric Oil Analysis Program (SOAP) used for?

Answer 36

To identify internal wear of lubricated engine components.

Question 37

What is the size range of particles that SOAP can detect in oil?

Answer 37

From 0.001 mm to 0.02 mm.

Question 38

What is the significance of monitoring metal particles in engine oil?

Answer 38

To identify increased wear for bearings and gears at an early stage.

Question 39

What does spectrometric analysis for oil samples help identify?

Answer 39

Metal particles suspended in oil ## Footnote Each metal produces a unique spectrum when vaporized, allowing for identification and quantification.

Question 40

How are oil samples for SOAP taken?

Answer 40

From the oil tank at regular intervals ## Footnote Samples are sent to a laboratory for analysis.

Question 41

What is the purpose of the high-voltage AC spark in spectrometric oil analysis?

Answer 41

To burn the film of oil on the rotating disk ## Footnote This allows light emitted to pass through slits for metal detection.

Question 42

What metals are commonly analyzed in turbine engine oils?

Answer 42

* Aluminium * Iron * Chromium * Silver * Copper * Tin * Magnesium * Lead * Nickel * Titanium ## Footnote Each metal has a specific threshold limit of contamination measured in parts per million.

Question 43

What is the threshold limit of contamination?

Answer 43

The maximum amount of normal wear for each metal ## Footnote It is measured by weight in parts per million (PPM).

Question 44

What do magnetic chip detectors do?

Answer 44

Catch metal particles attracted to the magnet ## Footnote They provide a quick assessment of oil condition.

Question 45

How can the condition of magnetic chip detectors be checked?

Answer 45

Manually at fixed intervals or electronically monitored ## Footnote They can be removed when necessary.

Question 46

What should be done before opening the oil tank filler cap after engine shut-down?

Answer 46

Wait at least five minutes ## Footnote This prevents hot oil from spraying out.

Question 47

What is the risk indicated by a fuel smell when opening the oil tank filler cap?

Answer 47

Leakage in the fuel-cooled oil cooler ## Footnote Further troubleshooting is required if this smell is detected.

Question 48

What are the two methods to replenish the oil system?

Answer 48

* Gravity filling * Pressure filling ## Footnote Gravity filling uses oil cans, while pressure filling uses an oil servicing system.

Question 49

Why is it important to monitor engine oil consumption?

Answer 49

To ensure proper maintenance and record keeping ## Footnote The quantity of oil added should be entered in the aircraft's technical logbook.

Question 50

True or False: The oil tank is usually located below the level of the gearbox.

Answer 50

False ## Footnote The oil tank is located above the gearbox.

Question 51

Fill in the blank: Spectrometric oil analysis provides invaluable information to help determine the source of _______.

Answer 51

Contamination ## Footnote Engine manufacturers provide lists of engine components for troubleshooting.