M15.9 Lubricants and Fuels Flashcards
What were the earliest gas turbine engines developed using?
Straight mineral oils
What operational requirements led to the evolution of oils with lower viscosities?
Low-temperature starting and re-lights
Why were mineral oils found unsuitable for modern gas turbine engines?
Lack of stability, excessive volatility, and thermal degradation at high temperatures
What type of oils were developed to meet the requirements of gas turbine engines?
Ester-based synthetic oils
What was the initial viscosity of the synthetic oils developed for gas turbine engines?
Approximately 3 centistokes (3 mm2/s at 100 °C)
What modifications were made to improve the load-carrying capability of synthetic oils?
Thickeners were added to raise viscosity to about 7.5 centistokes (7.5 mm2/s at 100 °C)
What are the main tasks of oil on modern jet engines?
- Lubricating
- Cooling
- Cleaning
- Corrosion protection
What is the pour point of Type 2 oils for jet engines?
-57 °C
What is the flash point of Type 2 oils?
Higher than 250 °C
What does viscosity measure in engine oil?
The internal resistance of a fluid against deformation
What is oxidation resistance in engine oil?
The ability of oil to resist thickening when reacting with oxygen
What is thermal stability in the context of engine oils?
The resistance to decomposition of oil compounds at high temperatures
What are the two groups of engine oils?
- Synthetic oils
- Mineral oils
What are the three types of synthetic oils?
- 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
What are the advantages of synthetic oils?
- Better viscosity
- Better thermal stability
- High-pressure resistance
What is one disadvantage of synthetic oils?
High price
What are some key physical and performance properties that lubricants must exhibit?
- Viscosity Index
- Viscosity
- Pour point
- Flash point
- Pressure resistance
- Oxidation resistance
- Thermal stability
- Volatility
- Acidity
What is the definition of pour point?
The lowest temperature at which oil will visibly move in a test tube for 5 seconds
What is the significance of pressure resistance in engine oil?
It resists loads on bearings and prevents contact between moving surfaces
What is the definition of volatility in the context of engine oil?
The ease with which a liquid is converted into a vaporous state
What is the typical composition of kerosene fuel used in commercial gas turbine engines?
Approximately 16% hydrogen and 84% carbon
What are the four main types of turbine engine fuel?
- Jet A1
- Jet A
- Jet B
- JP 5
What is the flash point of JP 5 fuel?
Plus 65 °C
What are the main requirements of turbine engine fuels?
- Low freezing point
- Flash point low enough for ignition
- Low tendency to vaporize at high altitudes
- Widely available
- Adequate lubrication capabilities
What are common problems caused by water in fuel?
- Ice build-up
- Corrosion
- Engine power fluctuations
- Microbial growth
What is the purpose of anti-ice additives in aviation fuel?
To prevent ice formation in fuel
What do anti-oxidants do in aviation fuel?
Prevent the formation of gum deposits caused by oxidation
What is the role of static dissipator additives?
Reduce hazardous effects of static electricity in fuel transfer systems
What is rubber swelling in the context of oil performance?
The amount the oil will cause a rubber compound to swell
What is coking in engine oils?
The amount of carbon residue remaining after extreme heating
What is the definition of fuel density?
The ratio between mass and volume of the fuel
What do corrosion inhibitors protect?
Corrosion inhibitors protect ferrous metals in fuel handling systems
Examples include pipelines and fuel storage tanks.
What is the function of metal de-activators?
Metal de-activators suppress the catalytic effect that some metals have on fuel oxidation
Particularly effective against copper.
What is the health risk associated with engine oil under normal conditions?
Low health risk for humans
Individual reactions may vary.
What should be done if engine oil is ingested?
Seek immediate medical assistance and provide details of the product and quantity ingested.
What are the effects of prolonged breathing of hydrocarbon vapour concentrations above prescribed limits?
Light-headedness, dizziness, or nausea.
What should be done in case of skin contact with engine oil?
Wash the skin thoroughly with soap and warm water and remove oil-soaked clothing.
What safety equipment should be used when handling engine oil?
Protective clothing, gloves, and eye protection.
What happens to synthetic oils when exposed to extremes of temperature?
They are not storage stable and their shelf life should be checked before use.
Why should open containers of synthetic oil not be reused?
Synthetic oil is hygroscopic and will absorb moisture from the atmosphere.
What special safety precautions are required when handling jet fuels?
Bonding and earthing are essential; flow rates must be restricted.
What should be done in case of a small spillage of jet fuel?
Remove with commercial absorbing agents.
What is the correct action if fuel comes in contact with the skin?
Wash thoroughly with soap and water.
What should be done if fuel enters the eyes?
Flush with plenty of clean water for up to 10 minutes and seek medical advice.
What are the risks associated with fuel leaks?
Refuelling malfunctions or damage to the aircraft.
What is the first step to take when dealing with a fuel spillage?
Stop the leakage flow.
What is prohibited near an aircraft to reduce fire hazard?
No naked flames and no smoking.
What must not be done when the aircraft engines are running?
Refuelling is not allowed.
What types of activities can create sparks near an aircraft?
Electrical switching, HF transmission, weather radar operation, metal parts striking together, electric static discharge.
What type of tools must be used when working in a fuel tank?
Explosion-proof tools.
What type of clothing should be worn when entering a fuel tank?
Special cotton clothing that will not create electric static charges.
Fill in the blank: Jet fuel should not be used for _______.
cleaning purposes.
