lubrication

Question 1

what is the main function of a lubricant? (3)

Answer 1

• must lubricate the moving parts of the engine
• cool the engine
• clean engine

Question 2

how does oil lubricate?

Answer 2

The constant flow of oil reduces friction and conducts heat away from surfaces of metal. heat that’s carried away by circulating oil is then cooled by an air cooler.

Question 3

oil tends to do what and prevent what? regarding combustion chambers.

Answer 3

seal combustion chambers by filling the space between the cylinder walls and piston rings, preventing the flow of combustion gases past piston rings.

Question 4

what are the secondary functions of oil?

Answer 4

sealing - keeping pipes and line from leaking

cushioning - lessening the impact when two objects are pushed together.

Question 5

what are the types of oil? (3)

Answer 5

• straight mineral oil, the disadvantage that they tend to oxidise while in the engine producing sludge and carbon deposits that block the oil galleries, pipes and filters.
• detergent oil, oil that cleans an engine but form compounds from metallic ash which blocks lines and filters.
• ashless dispersant oil, formulated so no deposits are formed and is the one used in aircraft.

Question 6

how are oils graded?

Answer 6

oil grade is given as a number. aircraft engines are usually given in a commercial aviation number.

“flying is twice as good as driving a car” SAE is double e.g 80 grade CAN oil = 40 SAE.

Question 7

what does SAE mean?

Answer 7

society of autmotive engineers number

Question 8

how does a dry-sump system work?

Answer 8

stores oil in a separate tank and scavengers the oil sump, leaving it essentially dry.

Question 9

how is the condition of an oil system monitored?

Answer 9

using cockpit gauges, two gauges are used. an oil pressure gauge and an oil temperature gauge.

Question 10

oil pressure is measured in what?

Answer 10

psi (pounders per square inch)

Question 11

oil temperature indicated is measured in what?

Answer 11

degrees celsius or Fahrenheit with both being redline for max and min and operating parameters being colour coded.

Question 12

how is oil quantity measured? and what happens if oil is too low or high?

Answer 12

checked prior to flight, the wet-sump engine will have a dipstick which is calibrated to slow quantity of oil present.

if the oil level is too low, oil overheats and pressure may be too low or may fluctuate. if too high excess oil will be forced out of the engine.

Question 13

how does oil cool?

Answer 13

it’s pumped around the engine including through the engine block.

The channels in the engine through which the oil travels are called galleries and as it moves through the galleries it absorbs heat from the engine.

Question 14

how does oil clean?

Answer 14

foreign materials are picked up by the oil and removed via an oil filter. that’s why the oil and filter need to be changed regularly.

Question 15

when should oil be changed?

Answer 15

every 50 hours of engine time.

Question 16

what is viscosity?

Answer 16

how thick a fluid is.

Question 17

what happens to the lubricating properties of oil with changing the temperature of an engine?

Answer 17

An increase in temperature can cause a reduction in viscosity, so as the oil heats up, it gets thinner meaning to lubricate less effectively than when it’s cold.

Question 18

how does a wet sump system work?

Answer 18

when the system isn’t working gravity drains the oil from the bottom of the engine to the sump and since they have no separate oil tank the sump acts as the tank.

Question 19

how does a dry-sump system work?

Answer 19

collects small amount of oil at the sump due to gravity, and the main system allows for the oil to be pumped into a tank which a separate pump is then used to push it around the engine

Question 20

what are oil pumps?

Answer 20

gear type pumps and as the oil runs through them they are also self-lubricating.

Question 21

how do oil pumps work?

Answer 21

powered by the engine usually being run from the accessory housing of the engine.

Question 22

what do oil filters do? and what can water do to it?

Answer 22

filter out much of the foreign matter which finds its way into the oil system.

if in the oil filter it can cause the chemical composition of the oil to start breaking down and forming by-products.

Question 23

why is checking oil quantity in pre-flight important?

Answer 23

too much oil can damage an engine and too little will mean that the 3 main functions of oil cannot be carried out

Question 24

why should you not over tighten the dipstick?

Answer 24

as the engine heats up and expands it can damage the dipstick shaft.

Question 25

oil pressure during checkups must rise within what time frame and if it doesn’t what does this mean?

Answer 25

30 seconds.

the worst-case scenario is that the oil is not free to circulate around the engine for some reason and may cause the engine to seize so you must shut down the engine ASAP.

Question 26

what does it mean if the oil pressure gauge is fluctuating from normal to low, backwards to forwards?

Answer 26

the most common issue is low oil quantity. could be caused by an oil pump failure (oil not being pumped around the engine) or an oil leak.

Question 27

what does it mean if there is an indication of high oil pressure?

Answer 27

the pressure relief valve is no longer working correctly. As its main job is to stop oil pressure from becoming too high, meaning that if it’s broken you can’t do much.

Question 28

if oil pressure becomes too high what can occur?

Answer 28

oil pressure can damage seals and connections, and if these break or burst then an oil leak might occur.

Question 29

if oil pressure reads zero what does this mean?

Answer 29

there is no oil left in the oil reservoir.

Question 30

what causes high oil temperature readings?

Answer 30

running the plane on a hot day at lower altitudes and at high power settings is the main problem regarding it.

Question 31

what should you do if you are reading high oil temperatures?

Answer 31

not a good idea to continue running with it so adding more cooling airflow to the engine using stuff like cowl flaps may help.

Question 32

what does it mean if the oil temperature is high and at the same time oil pressure is low?

Answer 32

something is not right with the engine, and these two happening at the same time could suggest an oil leak has happened.

Question 33

what should you do if the oil temperature is high and oil pressure is low?

Answer 33

land ASAP and check for leaks.

Question 34

what can you do if oil pressure reads high?

Answer 34

nothing during flight so landing ASAP should be the go.

Question 35

Procedure for filling oil

Answer 35

Unscrew cap and use funnel to put oil in