15.9 Flashcards
Why are mineral oils bad?
Lack stability, thermal degradation and excessive volatility
What bad about mineral oils sucessor, Esther based synthetic oils?
Low viscosity so insufficient load carrying capability
How was the problem of Esther based synthetic oils overcome?
By adding additives
What are Type 1 oils?
Low viscosity so required additives
What are second generation oils?
Oils that were based on hindered Esthers (Improvement of thermal stability and load carrying)
What are third generation oils?
Oils that have thermal stability?
What are the main tasks of oil on modern jet engine?
Cleaning
Corrosion resistance
Cooling
Lubrication
What does the oil do with the carried particles it cleans off of a surface?
Passes it through a filter
Two groups of engine oils?
Synthetic
Mineral
What are the thee types of synthetic oils?
Type 1 - Old aircraft
Type 2 - Modern aircraft
Type 3 - Special aircraft (Higher stability and viscosity at higher temperatures)
Advantages of synthetic oils?
Better viscosity, high pressure resistance, and better thermal stability
Disadvantage of synthetic oils?
They are expensive
What is viscosity index?
Effect temperature has on the viscosity on the oil. (The higher the number the least effected by change)
What is viscosity?
a fluids internal resistance against deformation
What does the viscosity of oil depend on?
High at low temp
Low at high temp
What is the pour point?
The lowest temperature the oil will visibly move
Type 2 oils have a pour point of what degree?
-57 degrees
What is a flash point?
The lowest temperature in which the oil will give off enough vapour to flash when a flame is applied
What should the flashpoint be in an engine?
High
Type 2 oils have what degree of flash point?
Above 250 degrees
What is pressure resistance?
Capability of an oil film between two components
What is oxidation resistance?
The reaction between oil and oxygen
What happens when oil reacts with oxygen?
It gets thicker and therefore the velocity increases
When does oil start to react with oxygen?
When certain temp increases above a certain level. It increases the durability
What is thermal stability?
Oil’s resistance to the break down of oil compounds at high temps
What is volatility?
The measure of ease at which a liquid is converted to a vapours state
What is acidity?
A measure of corrosive tendencies of a oil
What 6 factors affect the performance of oil?
Oil foaming
Rubber swelling
Oxidisation and thermal stability
Corrosiveness
Pressure
Coking
What is oil foaming?
The measure of resistance of oil being separated from trapped air
What is rubber swelling?
Amount of oil causing a rubber compound to swell
What is oxidisation and thermal stability?
The ability of the oil to resist the formation of hard carbon and sludge at high temperatures
What is corrosiveness?
What material does it effect?
The effect oil has on materials ESPECIALLY copper
What is pressure?
The ability of an oil to carry a load
What is coking?
Amount of carbon residue remaining in the oil after being subjected to extreme heating
Where is the Kerosene fuel most commonly used in commercial gas turbine engines?
Jet A and Jet A1
What is kerosene refined from?
Crude oil
What are the main 4 types of turbine engine fuel?
Jet A1, Jet A, Jet B, JP5
What is the most common fuel used in Europe for commercial jets?
Jet A1
What is the American name for Jet A1?
JP 1A
What is the most commonly used fuel type for jet engines in America?
Jet A
What is Jet A also referred to in the USA?
JP 1
What fuel can be an alternative to Jet A1?
Jet B
What is bad about Jet B?
It has a higher flammability with a flashpoint of -20 degrees (Difficult to handle)
What is an advantage about Jet B?
It Is used in colder weather
What is JP 5?
Military type jet fuel
Why is JP 5 preferred by military on a/c carriers?
It has a very high flash point of 65 degrees (safe to handle)
Low freezing point of -48 degrees
What must be recorded when refuelling?
The type of fuel used
What is the American name for JP 5?
JP 1A
What are the main requirements for turbine engine fuels?
Has a low freezing and flash point, low enough to provide good ignition but high for safe handling
What appearance must the fuel exhibit?
Clear
Bright
Visually free from solid masses
What composition must the fuel exhibit?
Limited acidity
A fuel with high volatility is desired for what?
A highly volatile fuel is very desirable for engine starts in cold weather and in flight
A fuel with low volatility is desired for what?
To eliminate vapour lock and reduce fuel losses via evaporation
What is the maximum viscosity of fuel?
-20 degrees
What 2 materials are susceptible to corrosion?
Copper
Silver
When must turbine engine fuels have a low tendency to vaporise?
In high flight altitudes
When does Jet fuel vaporise?
If the ambient pressure decreases
What is fuel density the ratio between?
The ratio between mass and volume
What 2 things does the density change with in regards to fuel?
Type
Temperature
At a temperature of 15 degrees what density does jet A1 and jet A have?
0.81kg/ltr
What can remove dirt in fuel and oil systems?
Filters (water will always be found in fuel)
What 2 conditions can fuel carry water in?
Dissolved (invisible) or suspended (Small droplets and water bubbles)
At what temperature does ice build up due to water?
0 degrees
What 3 things can water cause in the fuel system?
Corrosion
Engine power fluctuations/flameouts
Microbial growth
What maintenance can be done to avoid problems of water in fuel?
Monitor and remove the water periodically
What unit are fuel additives measured in?
Parts per million (ppm)
What is a fuel anti ice additive also known as?
Prist (Glycol anti freeze)
What allows microbes to assemble, grow and live on the fuel?
The greater presence of water
How do you prevent microbial contamination considering water is always present?
Have areas where water can settle and microbes to flourish
What disadvantages do anti ice additives inhibit?
Bacterial growth
What must you avoid to prevent water from appearing?
Having fuel in a fuel tank for a prolonged period
What do anti oxidants prevent?
The formation of gum deposits
What causes gum deposits?
Oxidisation
What do static dissipator additives reduce the effects of?
Static electricity generated by the movement of fuel
What do corrosion inhibitors protect from corrosion?
Ferrous metals in fuel handling systems
What do metal deactivators suppress?
The catalytic effect that some metals have on fuel oxidisation
What metal do metal deactivators suppress the catalytic effect it has on fuel oxidisation?
Copper
What involving your mouth should you never do in regards to fuel?
Siphon it
What involving your mouth should you never do in regards to oil?
Siphon it
If engine oil is ingested what must you provide details about?
The product and how much of it was ingested
What can prolonged or repeated contact with engine oil cause?
Irritation and dermatitis (so wash off with warm water)
What must you do if you get engine oil in your eye?
Clean your eye out with fresh water
What can engine oil do to paint when split, so what must you do to protect it?
It can discolour blister or remove, so wipe it clean with a petroleum solvent
Why should open containers of synthetic oil not be reused?
Because they are hydroscopic so will absorb moisture from the atmosphere to render it useful
Can you mix oils?
No
What accumulates with high furl rates?
Static electrical charges
What restrict fuel flow?
Diameter of the hose
What is essential do deal with static electrical charges?
Bonding and earthing
How can you remove small amounts of spillage?
With a commercial absorbing agent
How do you remove large amounts of spillage?
Plenty of water ensuring it does not enter drainage systems
How long should you wash your eye out with water after fuel gets in it?
10 minuets
How much water should you drink if you ingest fuel?
250ml
How are fuel leaks caused?
By malfunctions or damage
Where do refusing leaks occur?
At the vent tank opening
After you stop the leakage flow what must you do?
Add a binding agent to the fuel spillage
What shall not be operated near or below a vent tank?
Car engine
When can you not refuel?
When the engines are running
What tools must you use in a fuel tank?
Explosion proof tools, this includes communication systems
What clothing must you wear when entering a tank?
Cotten to not create electrostatic charging
