15.9 Lubrication and Fuels Flashcards
What were the earliest gas turbine engines developed using?
Straight mineral oils
These oils had low-temperature starting issues.
What operational requirements led to the evolution of oils with lower viscosities?
Low-temperature starting requirements
This includes starting on the ground or at altitude (re-lights).
What issues were found with mineral oils in gas turbine engines?
Lack of stability, excessive volatility, thermal degradation
These issues arose at higher temperatures.
What type of oils were developed for gas turbine engine lubricants?
Ester-based synthetic oils
These oils were more suitable for high-performance engines.
What viscosity did the initial ester-based synthetic oils have?
Approximately 3 centistokes
This was insufficient for high gear loads.
What was added to the initial synthetic oils to improve their performance?
Thickeners
This raised the viscosity to about 7.5 centistokes.
What are Type 1 oils known for?
Reliance on additives and multi-component additive packages
These were necessary to improve performance.
What does APU stand for?
Auxiliary Power Units
APUs are increasingly using 3 mm²/s oils.
What is the demand for engine oils in the USA due to?
Improved thermal stability and high load-carrying ability
Some sacrifice in low-temperature performance is accepted.
What are the main tasks of oil in modern jet engines?
- Lubricating
- Cooling
- Cleaning
- Corrosion protection
Each task is crucial for engine operation.
What is the purpose of lubrication in engine oil?
To reduce friction between moving metal surfaces
This prevents wear and damage.
What temperature does Type 2 oils have a pour point of?
-57 °C
Below this temperature, the oil stops flowing.
What is the flash point of Type 2 oils?
Higher than 250 °C
This helps avoid fire hazards.
What does viscosity measure in engine oil?
The internal resistance of a fluid against deformation
It affects how the oil flows and lubricates.
What is the viscosity range for Type 2 oils at 99 °C?
Higher than 5 cS and lower than 13,000 cS at -40 °C
This ensures proper performance under various temperatures.
What is oxidation resistance in engine oil?
The oil’s ability to resist thickening when reacting with oxygen
Important for maintaining durability.
What defines thermal stability in engine oil?
Resistance to decomposition of oil compounds at high temperatures
This ensures consistent lubrication capabilities.
What are the two main groups of engine oils?
- Synthetic oils
- Mineral oils
Synthetic oils are preferred for jet engines.
What is a key disadvantage of synthetic oils?
High price and harmful to the skin
They cannot be mixed with oils from other manufacturers.
What are the four main types of turbine engine fuel?
- Jet A1
- Jet A
- Jet B
- JP 5
Each has different specifications and uses.
What is the flash point minimum for Jet A1 fuel?
38 °C
This is important for safe handling.
What are the main requirements of turbine engine fuels?
- Low freezing point
- High flash point
- Clear appearance
- Limited acidity
- Low volatility
- Good fluidity
- High calorific value
- Stability against contamination
These ensure performance and safety.
What is the main purpose of additives in engine oil?
To impart desirable characteristics
Additives can include detergents, antioxidants, and foam inhibitors.
What is the impact of oil foaming on performance?
It affects the oil’s ability to separate from entrapped air
Foaming can reduce lubrication efficiency.
What is the significance of corrosion resistance in engine oil?
To prevent damage to engine components, especially metals
This is crucial for longevity.
What does the term ‘volatility’ refer to in fuel properties?
The ease with which a liquid is converted to vapor
High volatility is desirable for cold starts.
What is the maximum thermal stability of turbine engine fuels?
Deposits forming at varying temperatures
This refers to the ability of the fuel to maintain performance without forming deposits under different temperature conditions.
What contaminants are monitored in turbine engine fuels?
Maximum copper, existent gum and water reaction
Contaminants can affect fuel performance and engine health.
What is the importance of electrical conductivity in turbine engine fuels?
Minimum and maximum electrical conductivity
Conductivity can affect the performance and safety of the fuel.
What are the maximum limits for additives in turbine engine fuels?
Maximum anti-oxidants and static dissipator
Additives help in maintaining fuel quality and preventing issues.
What is a key characteristic of jet fuel regarding vaporization?
Low tendency to vaporise in high flight altitudes
This ensures fuel remains in liquid form at high altitudes.
What is the density of Jet A1 and Jet A at 15°C?
0.81 kg/ltr
Density is crucial for fuel management and performance.
List the main requirements for turbine engine fuel.
- Low Freezing Point
- Flash Point low enough for ignition
- Low Tendency to Vaporise in High Altitudes
- Widely Available
- Low Tendency to Carry Water
- High Volatility for Engine Starts
- Available all Over the World
- Adequate Lubrication Capabilities
- Low Tendency to Hold Water
These requirements ensure safe and efficient engine operation.
What issues can water in fuel cause?
- Ice build-up if fuel cools below 0 °C
- Corrosion in fuel system components
- Engine power fluctuations or flameouts
- Erratic fuel quantity indications
- Support for microbial growth
Water contamination poses significant risks to engine performance and safety.
How can water be present in fuel?
- Dissolved in fuel (invisible)
- Suspended in fuel (visible as droplets)
Both forms of water can lead to various issues in the fuel system.
What method is commonly used to check for water in fuel?
Syringe test cartridge
This method involves drawing fuel through a chemically treated filter to detect water presence.
What happens if water is detected in fuel?
The tank is required to be drained, refilled, and tested again
This is necessary to prevent issues related to water contamination.
What are fuel additives?
Compounds added to fuel in very small quantities to provide special or improved qualities.
How are fuel additives measured?
In parts per million (ppm).
What controls the quantity and approval of fuel additives?
Manufacturer’s specifications for each specific fuel.
What is the purpose of anti-ice additives?
To lower the freezing point of water in fuel and prevent icing.
What is an example of an anti-ice additive?
Prist®.
How do anti-ice additives work?
They dissolve in free water and lower its freezing point.
What are the unique purity issues related to jet fuel?
Presence of water and fuel-consuming microbes.
Why is microbial contamination a threat in engine fuels?
Engine fuels always contain water, allowing microbes to grow.
Where do microbes thrive in aircraft fuel systems?
In areas where water settles in the fuel tanks.
What is a biofilm?
A layer formed by microorganisms that can clog filters and corrode tank coatings.
How can microbial growth be controlled in fuel?
By using a biocide additive.
What practices should be followed to minimize water in fuel?
Avoid prolonged storage and regularly monitor for settled water.
What are anti-oxidants used for in fuel?
To prevent gum deposits and inhibit peroxide formation.
What do static dissipator additives do?
Reduce the hazardous effects of static electricity in fuel transfer.
True or False: Static dissipator additives eliminate the need for bonding in fuel systems.
False.
What do corrosion inhibitors protect?
Ferrous metals in fuel handling systems from corrosion.
What is the effect of metal de-activators?
They suppress the catalytic effect of metals on fuel oxidation.
What should be minimized when handling engine oil?
Exposure to vapours and mist
Prolonged breathing of hydrocarbon vapour concentrations above prescribed limits could result in light-headedness, dizziness, or nausea.
What does MSDS stand for?
Material Safety Data Sheets
MSDS provides information on limits of exposure to engine oil.
What should you do if engine oil is ingested?
Seek immediate medical assistance and provide details of the product and amount ingested.
What is the recommended action in case of skin contact with engine oil?
Wash the skin thoroughly with soap and warm water.
What type of protective gear should be used when handling engine oil?
Protective clothing, gloves, and eye protection.
What happens to engine oil when subjected to very high temperatures?
It can break down and produce a product of unknown toxicity.
What is the shelf life consideration for synthetic oils?
Synthetic oils are not storage stable and should be checked before use.
What should be avoided when using open containers of synthetic oil?
Reuse of open containers.
What effect do synthetic oils have on certain materials?
They tend to damage some types of paints, electrical insulation, and elastomer materials.
What safety precautions are required when handling jet fuels?
Bonding and earthing (grounding) are essential.
What should be done in case of a small fuel spillage?
Remove with commercial absorbing agents.
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 is the recommended action if fuel is ingested?
Do not induce vomiting; drink 250 ml (1/2 pint) of water and obtain medical attention.
What should be done immediately if a fuel leak occurs?
Stop the leakage flow and add a binding agent to the fuel spillage.
True or False: Refuelling is allowed when the aircraft engines are running.
False
What sources of heat are prohibited near the aircraft?
Naked flames and smoking.
What must be connected to prevent electric static discharge during refuelling?
The fuel truck must be connected to the aircraft by a grounding lead.
What type of tools should be used when working in a fuel tank?
Explosion-proof tools.
What type of clothing should be worn when entering a fuel tank?
Cotton clothing that will not create electric static charges.
What can create sparks near an aircraft?
Electrical switching, HF transmission, weather radar operation, metal parts striking together, electric static discharge.
