Lubrication Flashcards
What are the primary and secondary purposes of lubrication?
Reduce friction
&
Cooling
How is oil grade determined?
-Operating loads
-Rotational speed of components
-Operating temperatures
What are the 5 functions of lubrication?
Cools
Seals
Cushions
Cleans
Prevents corrosion
What has the greatest effect on viscosity?
Temperature
What is viscosity index?
States the rate of change in viscosity with a change in temperature
(Higher index rating = less effected by temp)
Three reasons for the viscosity index?
1.Large engine operating clearances
2.High operating temperatures
3.High bearing pressures
Aircraft oils are rated with a _______ number.
Saybolt
(Determined by the number of seconds it takes for 60 cc’s of material to drain through a calibrated orifice at a specific temperature)
Multi-viscosity oils use ____ numbers.
SAE
(Converted from the Saybolt number)
What are the 4 lubrication types?
Animal based
Vegetable based
Mineral based
Synthetic
What are the most commonly used lubrication types in aviation?
Mineral
&
Synthetic (Semi-synthetic)
Oils with the same Mil Spec may be interchanged as long as what?
They are the same grade
What are the three states of lubricants?
Solid
Semisolid
Liquid (fluid)
What is pour point?
Lowest temperature at which oil will pour without being disturbed
What is cloud point?
Temp at which wax content begins to solidify and the oil becomes cloudy
What is flash point?
When oil will flash but not burn
What is fire point?
When oil is hot enough to continue to burn
What oils may not be mixed?
Mineral based and synthetic
Oil systems can be one of two types. What are they?
Dry sump or Wet sump
What is the difference between Dry and Wet sump types?
Wet
-Oil supply is carried in the engine
-No scavenger pump
Dry
-Oil is carried in a tank separate from the engine
-Has scavenger pump
What are the 3 methods of internal lubrication?
Pressure
Spray
Splash
Oil tanks must be able to withstand how much pressure?
5 psi
FAR 33.71 requires what?
On or around the filler opening must be marked with the word “OIL”
An expansion space of ______ tank capacity or ______, whichever is greater, must be provided for oil tanks.
10%
1/2 Gallon
What is a hopper tank used for?
Oil dilution and aids in quick warming of the oil
What are 3 types of oil pumps?
Vane type
Gear type
Gerotor
Oil pumps must have what in order to bypass extra oil?
Pressure relief valve
What are the two types of oil filter systems?
Full Flow
By-pass
What are the differences between the Full-flow and By-pass type oil filter systems?
Full-flow
-Filters all the oil at once
-Has bypass valve to allow oil passage if filter becomes clogged
-In Series
By-pass
-Filters the oil in portions
-In parallel
What are 3 types of filter constructions?
Screen type (reusable)
Cuno (Discs and Spacers)
Spin-on (Cartridge, Most common)
What are oil coolers for?
Fluid to fluid heat exchanger
Transfers heat from oil to air or fuel
How do you determine oil temp in wet and dry sumps?
Sensing bulb
