M15.10

Question 1

What is the purpose of a turbine engine lubrication system?

Answer 1

To lubricate, cool, clean, and protect engine bearings and gearboxes.

Question 2

What are the two main types of turbine engine lubrication systems?

Answer 2

Wet sump systems and dry sump systems.

Question 3

What is a wet sump lubrication system?

Answer 3

A system where oil is stored within the engine.

Question 4

What is a dry sump lubrication system?

Answer 4

A system where oil is stored in an external tank and circulated by pumps.

Question 5

What are the two classifications of lubrication systems by pressure control?

Answer 5

Full-flow systems and constant pressure (regulated) systems.

Question 6

What characterises a full-flow lubrication system?

Answer 6

Oil pressure varies with engine speed, oil temperature, and system leakage.

Question 7

What are advantages of full-flow systems?

Answer 7

Simple design and widely used.

Question 8

What are disadvantages of full-flow systems?

Answer 8

Very high oil pressure at high speeds and higher oil temperature after power reduction.

Question 9

What characterises a constant pressure lubrication system?

Answer 9

Oil pressure is maintained at a fixed value regardless of engine speed or temperature.

Question 10

How is constant oil pressure maintained?

Answer 10

By a pressure-regulating valve.

Question 11

List the four main lubrication system subsystems.

Answer 11

Oil reservoir and supply, scavenge system, vent (breather) system, monitoring system.

Question 12

What material are oil tanks typically made from?

Answer 12

Fire-resistant aluminium.

Question 13

Why are oil tanks slightly pressurised?

Answer 13

To ensure positive oil flow to the pump.

Question 14

Typical oil tank pressurisation value?

Answer 14

Approximately 4 psi.

Question 15

What components are commonly found on oil tanks?

Answer 15

Strainers, check valves, sight glasses, scuppers, and deaerators.

Question 16

How is oil cooled in large jet engines?

Answer 16

By fuel-cooled oil coolers.

Question 17

How is oil cooled in turboprops and APUs?

Answer 17

By air-cooled oil coolers.

Question 18

What is a hot tank lubrication system?

Answer 18

Oil is cooled after leaving the tank.

Question 19

What is a cold tank lubrication system?

Answer 19

Oil is cooled before returning to the tank.

Question 20

What are the two main types of oil pumps used?

Answer 20

Gear pumps and gerotor pumps.

Question 21

Which oil pump type is most common?

Answer 21

Gear pumps.

Question 22

What are advantages of gerotor pumps?

Answer 22

Compact, efficient, and capable of multi-element operation.

Question 23

How are oil pumps usually driven?

Answer 23

By the accessory gearbox.

Question 24

What is the function of a pressure regulating valve?

Answer 24

To maintain constant oil pressure.

Question 25

What is the function of a pressure relief valve?

Answer 25

To protect the system from overpressure.

Question 26

What is the purpose of bypass valves?

Answer 26

To bypass filters or coolers when oil is cold or components are blocked.

Question 27

What type of bypass valves are commonly used in modern systems?

Answer 27

Thermostatic bypass valves.

Question 28

What is the purpose of oil filtration?

Answer 28

To protect pumps, bearings, and oil nozzles from contamination.

Question 29

Name common oil filtration components.

Answer 29

Suction screens, pressure filters, scavenge filters, bypass valves, clogging indicators.

Question 30

What is a last-chance filter?

Answer 30

A screen located upstream of oil nozzles to catch final debris.

Question 31

What is the function of the scavenge system?

Answer 31

To return used oil and contaminants to the oil tank.

Question 32

Where does scavenged oil come from?

Answer 32

Bearing compartments and gearboxes.

Question 33

What is the purpose of the vent (breather) system?

Answer 33

To remove air and prevent pressure build-up in bearing compartments.

Question 34

Why must bearing compartments be vented?

Answer 34

To prevent oil being forced past seals into the compressor.

Question 35

How is air removed from oil in the tank?

Answer 35

By a deaerator.

Question 36

Where is vented air discharged?

Answer 36

Overboard.

Question 37

Why are vents screened and baffled?

Answer 37

To prevent oil loss during manoeuvres.

Question 38

What parameters are monitored by the lubrication monitoring system?

Answer 38

Oil quantity, oil pressure, oil temperature, and oil condition.

Question 39

How do capacitance oil quantity transmitters work?

Answer 39

By measuring changes in dielectric constant as oil level changes.

Question 40

How do reed switch oil quantity transmitters work?

Answer 40

Using a float and reed switches to vary electrical resistance.

Question 41

What contaminates engine oil over time?

Answer 41

Wear particles, degraded additives, water, and dust.

Question 42

What is the purpose of debris monitoring systems?

Answer 42

To assess internal engine wear by tracking particles.

Question 43

What is the function of magnetic chip detectors?

Answer 43

To capture ferrous particles from the oil.

Question 44

How can magnetic chip detectors provide warnings?

Answer 44

Metal bridges magnets causing a resistance change and indication.