15.9 Flashcards
Two types of oils?
Mineral oils
Synthetic oils
Where are mineral oils only used?
Piston engines
What are the main tasks of oil on modern jet aircraft?
Lubrication
Cooling
Cleaning
Corrosion protection
What are the three types of synthetic oils?
Type 1
Type 2
Type 3
What is a type 1 synthetic oil?
First generation- only used on older gas turbine engines
What is the type of synthetic oil used on modern gas turbine engine?
Type 2
Describe type 3 synthetic oil?
Has higher thermal stability and viscosity at high temperatures
Used on special aircraft
Advantages of synthetic oils?
Better viscosity
Good thermal stability
High pressure resistance
Disadvantages of synthetic oils?
Higher price
Can’t be mixed with other manufactured oils
What is the viscosity index?
Effect temperature has on viscosity of the oil.
Higher number=least affected by a change in temperature
What is the pour point?
Lowest temperature that oil will visibly move in a 31.75mm test tube held horizontally for 5 seconds
What is the flash point?
Lowest temperature oil will give off enough vapour to flash when flame is applied
What is the fire point?
Lowest temperature that the oil will ignite and burn continuously for at least 5 seconds
What is volatility?
Measure of ease in which a liquid is converted to a vaporous state
What is acidity?
A measure of the corrosive tendencies of the oil
What is oil foaming?
The measure of resistance of the oil to separate from entrapped air
What is rubber swelling?
Amount of oil that will cause a particular rubber compound to swell
What is oxidation and thermal stability?
Ability of oil to resist formation of hard carbon and sludge at high temperatures
What is corrosiveness?
The effect of oil on various metals, especially copper
What is pressure in relation to factors affecting oil performance?
Ability of the oil to carry a load
What is coking?
The amount of carbon residue remaining in the oil after being subjected to extreme heating.
What are factors that affect oil performance?
Water emulsion
Storage stability
Compatibility
Inter facial tension
Why would chemical additives be added to oils?
To impart desirable characteristics
Flash and freeze point for Jet A1
Flash- 38 degrees c
Freeze- -47 degrees c
Flash and freeze point for Jet A?
Flash- 38 degrees c
Freeze- -40 degrees c
Flash and freeze for Jet B?
Flash= 20 degrees c
Freeze= -60 degrees c
Flash and freeze point for JP5?
Flash= 65 degrees c
Freeze= -48 degrees c
What should be the appearance of fuel?
Should be clear, bright and visually free from solid matter and undissolved water at normal ambient temperature.
Different fuels have different freezing points due to their what?
Composition
When would a highly volatile fuel be desired?
For engine starts in cold weather and flight
Why would a low volatile fuel be desired?
To eliminate vapour lock and to reduce fuel losses by evaporation.
The required freezing point of fuel for turbine engines should be below what?
-40 degrees C
What are the main requirement for fuel?
Low freezing point
A flash point low enough for ignition and as high as possible for safe handling
Adequate lubrication
Low tendency to vaporise at high altitude
Low tendency to carry water
Widely available
Are synthetic oils storage stable?
No
Stored oil should be protected from what?
Extreme temperature
Why should opened containers of oil not be reused?
As synthetic oil is hygroscopic
Can you mix different branded synthetic oils?
No
If ingestion of oil takes place what should you do?
DO NOT induce vomiting
Drink 250ml of water and seek medical attention
When is refuelling not allowed?
When aircraft is running
Conditions that could create sparks?
Electrical switching
HF transmissions
Weather radar operation
Metal parts- struck together
Electric static discharge
Fuel truck must be connected to aircraft with what?
Grounding lead
Explosion proof tools are used where?
In fuel tanks
When can you enter a fuel tank without full face mask?
If tank is considered health safe
How is a health safe tank achieved?
Through good/sufficient ventilation
To get out of category 4 tank areas what must you use?
Mechanical cutters