M15.9 Lubricants and Fuels

Question 1

What were the earliest gas turbine engines developed using?

Answer 1

Straight mineral oils

Question 2

What operational requirements led to the evolution of oils with lower viscosities?

Answer 2

Low-temperature starting and re-lights

Question 3

Why were mineral oils found unsuitable for modern gas turbine engines?

Answer 3

Lack of stability, excessive volatility, and thermal degradation at high temperatures

Question 4

What type of oils were developed to meet the requirements of gas turbine engines?

Answer 4

Ester-based synthetic oils

Question 5

What was the initial viscosity of the synthetic oils developed for gas turbine engines?

Answer 5

Approximately 3 centistokes (3 mm2/s at 100 °C)

Question 6

What modifications were made to improve the load-carrying capability of synthetic oils?

Answer 6

Thickeners were added to raise viscosity to about 7.5 centistokes (7.5 mm2/s at 100 °C)

Question 7

What are the main tasks of oil on modern jet engines?

Answer 7

• Lubricating
• Cooling
• Cleaning
• Corrosion protection

Question 8

What is the pour point of Type 2 oils for jet engines?

Answer 8

-57 °C

Question 9

What is the flash point of Type 2 oils?

Answer 9

Higher than 250 °C

Question 10

What does viscosity measure in engine oil?

Answer 10

The internal resistance of a fluid against deformation

Question 11

What is oxidation resistance in engine oil?

Answer 11

The ability of oil to resist thickening when reacting with oxygen

Question 12

What is thermal stability in the context of engine oils?

Answer 12

The resistance to decomposition of oil compounds at high temperatures

Question 13

What are the two groups of engine oils?

Answer 13

• Synthetic oils
• Mineral oils

Question 14

What are the three types of synthetic oils?

Answer 14

• Type 1: First-generation synthetic oil
• Type 2: Mostly used on modern gas turbine engines
• Type 3: Higher thermal stability and viscosity, used on special aircraft

Question 15

What are the advantages of synthetic oils?

Answer 15

• Better viscosity
• Better thermal stability
• High-pressure resistance

Question 16

What is one disadvantage of synthetic oils?

Answer 16

High price

Question 17

What are some key physical and performance properties that lubricants must exhibit?

Answer 17

• Viscosity Index
• Viscosity
• Pour point
• Flash point
• Pressure resistance
• Oxidation resistance
• Thermal stability
• Volatility
• Acidity

Question 18

What is the definition of pour point?

Answer 18

The lowest temperature at which oil will visibly move in a test tube for 5 seconds

Question 19

What is the significance of pressure resistance in engine oil?

Answer 19

It resists loads on bearings and prevents contact between moving surfaces

Question 20

What is the definition of volatility in the context of engine oil?

Answer 20

The ease with which a liquid is converted into a vaporous state

Question 21

What is the typical composition of kerosene fuel used in commercial gas turbine engines?

Answer 21

Approximately 16% hydrogen and 84% carbon

Question 22

What are the four main types of turbine engine fuel?

Answer 22

• Jet A1
• Jet A
• Jet B
• JP 5

Question 23

What is the flash point of JP 5 fuel?

Answer 23

Plus 65 °C

Question 24

What are the main requirements of turbine engine fuels?

Answer 24

• Low freezing point
• Flash point low enough for ignition
• Low tendency to vaporize at high altitudes
• Widely available
• Adequate lubrication capabilities

Question 25

What are common problems caused by water in fuel?

Answer 25

* Ice build-up * Corrosion * Engine power fluctuations * Microbial growth

Question 26

What is the purpose of anti-ice additives in aviation fuel?

Answer 26

To prevent ice formation in fuel

Question 27

What do anti-oxidants do in aviation fuel?

Answer 27

Prevent the formation of gum deposits caused by oxidation

Question 28

What is the role of static dissipator additives?

Answer 28

Reduce hazardous effects of static electricity in fuel transfer systems

Question 29

What is rubber swelling in the context of oil performance?

Answer 29

The amount the oil will cause a rubber compound to swell

Question 30

What is coking in engine oils?

Answer 30

The amount of carbon residue remaining after extreme heating

Question 31

What is the definition of fuel density?

Answer 31

The ratio between mass and volume of the fuel

Question 32

What do corrosion inhibitors protect?

Answer 32

Corrosion inhibitors protect ferrous metals in fuel handling systems ## Footnote Examples include pipelines and fuel storage tanks.

Question 33

What is the function of metal de-activators?

Answer 33

Metal de-activators suppress the catalytic effect that some metals have on fuel oxidation ## Footnote Particularly effective against copper.

Question 34

What is the health risk associated with engine oil under normal conditions?

Answer 34

Low health risk for humans ## Footnote Individual reactions may vary.

Question 35

What should be done if engine oil is ingested?

Answer 35

Seek immediate medical assistance and provide details of the product and quantity ingested.

Question 36

What are the effects of prolonged breathing of hydrocarbon vapour concentrations above prescribed limits?

Answer 36

Light-headedness, dizziness, or nausea.

Question 37

What should be done in case of skin contact with engine oil?

Answer 37

Wash the skin thoroughly with soap and warm water and remove oil-soaked clothing.

Question 38

What safety equipment should be used when handling engine oil?

Answer 38

Protective clothing, gloves, and eye protection.

Question 39

What happens to synthetic oils when exposed to extremes of temperature?

Answer 39

They are not storage stable and their shelf life should be checked before use.

Question 40

Why should open containers of synthetic oil not be reused?

Answer 40

Synthetic oil is hygroscopic and will absorb moisture from the atmosphere.

Question 41

What special safety precautions are required when handling jet fuels?

Answer 41

Bonding and earthing are essential; flow rates must be restricted.

Question 42

What should be done in case of a small spillage of jet fuel?

Answer 42

Remove with commercial absorbing agents.

Question 43

What is the correct action if fuel comes in contact with the skin?

Answer 43

Wash thoroughly with soap and water.

Question 44

What should be done if fuel enters the eyes?

Answer 44

Flush with plenty of clean water for up to 10 minutes and seek medical advice.

Question 45

What are the risks associated with fuel leaks?

Answer 45

Refuelling malfunctions or damage to the aircraft.

Question 46

What is the first step to take when dealing with a fuel spillage?

Answer 46

Stop the leakage flow.

Question 47

What is prohibited near an aircraft to reduce fire hazard?

Answer 47

No naked flames and no smoking.

Question 48

What must not be done when the aircraft engines are running?

Answer 48

Refuelling is not allowed.

Question 49

What types of activities can create sparks near an aircraft?

Answer 49

Electrical switching, HF transmission, weather radar operation, metal parts striking together, electric static discharge.

Question 50

What type of tools must be used when working in a fuel tank?

Answer 50

Explosion-proof tools.

Question 51

What type of clothing should be worn when entering a fuel tank?

Answer 51

Special cotton clothing that will not create electric static charges.

Question 52

Fill in the blank: Jet fuel should not be used for _______.

Answer 52

cleaning purposes.