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Module 15 - Gas Turbine Engines > 15.9 - Lubricants and Fuels > Flashcards

15.9 - Lubricants and Fuels Flashcards

1
Q

What are the three main sources of lubricating oils?

A

Mineral
Synthetic
Vegetable

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2
Q

Why are synthetic oils used in jet engines over mineral oils?

A

They retain their lubricating properties and are more resistant to oxidation at higher temperatures

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3
Q

What is viscosity of a fluid?

A

The internal resistance of a fluid to deform under shear stress. It depends on temperature.

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4
Q

What is the pour point?

A

An oils temperature at which point when it is cooled down, means it cannot flow

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5
Q

What is the flash point?

A

The lowest temperature at which it becomes an ignitable mixture with air. It’s the liquid temperature at which the vapour is given off

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6
Q

What is the pressure resistance?

A

A load carrying capability of the oil when it forms a film between two parts. It’s resistance on the loads of the moving surfaces.

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7
Q

What is an oils oxidation resistance?

A

Ensures the oils resistance and durability.

Oxidised oil becomes thicker and increases viscosity, reducing the lubrication effect.

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8
Q

What is thermal stability of an oil?

A

The resistance of the oil to decomposition in high temperatures.

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9
Q

What additives can be added to oil?

A

Extreme pressure
Anti-corrosion
Detergent
Inhibitors

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10
Q

What is a detergent additive used for in engine oil?

A

They allow the oil to hold sludge or debris in suspension, preventing it from building up within the engine. It will be carried until trapped by filters.

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11
Q

What are inhibitors used for in oil?

A

Additives used to slow down the formation of oxidation products.

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12
Q

What can water or moisture do to a lubricating system?

A
  • breaks down heavily loaded surfaces
  • water and oil forms an emulsion, reducing its lubrication effect
  • water breaks down the additives in the oil
  • causes excessive frothing, with subsequent loss of oil through the vent systems
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13
Q

What types of fuel do international airliners use?

A

Jet-A and Jet-A1

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14
Q

What types of fuels are used by military jets?

A

Jet-B, Turbo fuel 5, JP-4 and JP-5

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15
Q

What are metal de-activators in fuel?

A

They suppress the catalytic effect which some metals, particularly copper, have on fuel oxidation.

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16
Q

What are biocide additives in fuel?

A

Reduces the risks of microbiological growths in the fuel systems. Biopic is well known.

17
Q

What types of tools should be used with fuel systems?

A

Spark-free

18
Q

What is a hydrokit used for?

A

Detecting in dissolved water quantities in turbine fuel

19
Q

What is the name of the microbiological fungus found in contaminated fuel?

A

Cladosporium Resinae

20
Q

What ratio of kerosene and air will burn effectively?

A

15 parts air to 1 part fuel

21
Q

What is an oils viscosity index based on?

A

It rate of change in viscosity with temperature change

22
Q

What is the resistance to flow of an oil known as?

A

It’s Viscosity

23
Q

The combined output from all of the scavenge pumps will be _______ than the pressure pump output.

A

Greater than the pressure pump output

24
Q

What is the typical operating PSI in a gas turbine lubricating system?

A

100psi

25
Q

How is a gear box breather prevented from leaking oil to the atmosphere?

A

An impeller and centrifugal force

26
Q

What is Jet B fuel?

A

A kerosene based fuel

27
Q

What is Reid vapour pressure?

A

It is the pressure exerted by a fuel when heated to 38 degrees C

28
Q

What happens to the weight of the fuel if the specific gravity is increased?

A

It increases

29
Q

To what condition does the fuel flow respond during aircraft acceleration?

A

The mass airflow through the engine

30
Q

To read oil pressure direct from the source, what system would you use?

A

A Bourdon tube

31
Q

What is an EP lubricant?

A

Extreme pressure - Used for gear-type pumps where high tooth pressures and high rubbing forces are present

32
Q

What is DERD 2494?

A

A kerosene based fuel

33
Q

What advantage do mineral oils have over vegetable oils in a turbine engine?

A

They are more chemically stable

34
Q

What should you do when servicing a felt-type filter?

A

Remove and replace the filter

Module 15 - Gas Turbine Engines (22 decks)

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