M15.9

Question 1

Why were early mineral oils unsuitable for gas turbine engines?

Answer 1

Poor low-temperature performance, high volatility, and thermal degradation at higher engine temperatures.

Question 2

What replaced mineral oils in gas turbine engines?

Answer 2

Ester-based synthetic oils.

Question 3

What are Type 1 turbine oils?

Answer 3

First-generation synthetic oils relying heavily on additives; now used mainly in older engines.

Question 4

What are Type 2 turbine oils?

Answer 4

Second-generation synthetic oils with improved thermal stability and load-carrying capability; widely used in modern engines.

Question 5

What are Type 3 turbine oils?

Answer 5

Third-generation oils with very high thermal stability and high-temperature viscosity for high-performance aircraft.

Question 6

What factors drove the development of advanced engine oils?

Answer 6

Increasing engine efficiency, operating temperature, and pressure.

Question 7

What are the four main functions of engine oil?

Answer 7

Lubrication, cooling, cleaning, and corrosion protection.

Question 8

What are the two main types of engine oil?

Answer 8

Mineral oils and synthetic oils.

Question 9

Why are synthetic oils preferred?

Answer 9

Superior viscosity control, thermal stability, and pressure resistance.

Question 10

What does viscosity measure?

Answer 10

An oil’s resistance to flow.

Question 11

What is viscosity index?

Answer 11

How much viscosity changes with temperature.

Question 12

What is the pour point of oil?

Answer 12

The lowest temperature at which oil will flow.

Question 13

Typical pour point of Type 2 oil?

Answer 13

Approximately −57 °C.

Question 14

What is flash point?

Answer 14

The temperature at which oil vapours ignite.

Question 15

Typical flash point of Type 2 oils?

Answer 15

Greater than 250 °C.

Question 16

Why is oxidation resistance important?

Answer 16

Prevents oil thickening and degradation at high temperatures.

Question 17

What is thermal stability?

Answer 17

Resistance to molecular breakdown at high temperatures.

Question 18

What does increasing oil acidity indicate?

Answer 18

Oil degradation and increased corrosion risk.

Question 19

List common engine oil additives.

Answer 19

Antioxidants, anti-wear agents, detergents, foam inhibitors, viscosity modifiers, pour point depressants.

Question 20

What is the main composition of turbine fuels?

Answer 20

Kerosene-based hydrocarbons refined from crude oil.

Question 21

Name common turbine engine fuels.

Answer 21

Jet A1, Jet A, Jet B, JP-5.

Question 22

Where is Jet A1 primarily used?

Answer 22

Europe.

Question 23

Why is Jet B used?

Answer 23

Improved cold-weather performance.

Question 24

Why does JP-5 have a high flash point?

Answer 24

For safer use on aircraft carriers.

Question 25

Why must fuel type always be recorded?

Answer 25

Different fuels have different characteristics and limitations.

Question 26

List key turbine fuel requirements.

Answer 26

Low freezing point, safe flash point, controlled volatility, stability, low corrosiveness, lubrication, minimal contaminants.

Question 27

What is the density of Jet A / Jet A1 at 15 °C?

Answer 27

0.81 kg/L.

Question 28

In what two forms can water exist in fuel?

Answer 28

Dissolved and suspended.

Question 29

What problems can water in fuel cause?

Answer 29

Ice formation, corrosion, flameouts, and microbial growth.

Question 30

What are fuel anti-ice additives used for?

Answer 30

Prevent ice formation in the fuel system.

Question 31

What is Prist®?

Answer 31

A commonly used fuel anti-ice additive.

Question 32

Why is jet fuel prone to microbial growth?

Answer 32

It retains water which supports microbial contamination.

Question 33

Name common aviation fuel additives.

Answer 33

Anti-oxidants, static dissipators, corrosion inhibitors, metal de-activators.

Question 34

What health hazards are associated with engine oil?

Answer 34

Respiratory irritation, dermatitis, eye irritation, and toxicity if ingested.

Question 35

What physical hazards are associated with engine oil?

Answer 35

Burns from hot oil and high-pressure injection injuries.

Question 36

How can engine oil damage aircraft materials?

Answer 36

It can damage paintwork, plastics, rubbers, tyres, and windows.

Question 37

What PPE should be used when handling engine oil?

Answer 37

Gloves, goggles, and protective clothing.

Question 38

What must be done before opening pressurised oil systems?

Answer 38

Allow the engine to cool and wait the specified depressurisation time.

Question 39

Why are turbine fuels particularly hazardous?

Answer 39

They are highly flammable and produce explosive vapours.

Question 40

What precautions are required when working with fuel systems?

Answer 40

Isolate fuel supply, release pressure, drain fuel safely, and follow fire precautions.