lubrication systems

Question 1

why is an oil tank required to have expansion space

Answer 1

to provide for thermal expansion and air in the return oil

Question 2

why must aircraft reciprocating engines use an oil with a relatively high viscosity

Answer 2

aircraft engines have large operating clearances, high operating temperatures, and high bearing pressures

Question 3

what is the function of a dispersant additive as contained in ashless dispersant oil

Answer 3

a dispersant helps keep an engine interior clean by keeping sludge forming contaminants in suspension in the oil until they can be trapped by filter or drained out at oil change

Question 4

what factors must an engine manufacturer consider in determining the proper grade of oil for an engine

Answer 4

operating load, rotational speeds, and operating temperatures

Question 5

what may happen to an oil that is too low in viscosity at engine operating temperatures

Answer 5

it is likely to become so thin that the oil film between moving parts is easily broken

Question 6

what is the most critical lubrication point in a gas turbine engine?

Answer 6

the turbine bearing

Question 7

what are two important characteristics relating to viscosity that an engine oil must possess

Answer 7

it must be light enough to circulate freely and heavy enough to provide the proper oil film at engine operating temperatures

Question 8

what is the primary purpose of an aircraft reciprocating engine lubricant

Answer 8

to reduce friction between moving parts

Question 9

what is the first thing to be done if metal particles are found in an engine oil filter

Answer 9

evaluate the finding according the manufacturer’s maintenance instructions

Question 10

what controls oil pressure in a gear-type oil pressure pump

Answer 10

an oil pressure relief valve

Question 11

what are two types of turbine engine oil coolers

Answer 11

air cooled and fuel cooled

Question 12

what could cause oil foaming

Answer 12

diluted oil, contaminated oil, and the oil level being too high

Question 13

what are some oil contaminants

Answer 13

moisture
acids
dirt
carbon
metal particles

Question 14

what type of oil is used in turbine engine oil systems

Answer 14

synthetic oil

Question 15

what could be the cause of excessive oil consumption without the evidence of oil leaks in a reciprocating engine?

Answer 15

worn or broken piston rings

Question 16

what would be an indication of an inadequate oil supply

Answer 16

low oil pressure and high oil temperature

Question 17

what would be an indication of an obstruction in oil cooler passages

Answer 17

high oil temperatures

Question 18

name at least two areas of a turbine engine oil system where oil screens/filters may be located

Answer 18

1. oil pressure system (main filters)
   2.scavenage system
2. at or just before the oil jets (last chance)

Question 19

what does the presence of metal particles in an engine oil filter indicate

Answer 19

possible engine internal failure

Question 20

what is the purpose of an oil cooler bypass valve

Answer 20

an oil cooler bypass valve directs the oil through or around the oil cooler to keep the oil temperature within operating limits

Question 21

where does the oil temperature bulb usually sense oil temperature

Answer 21

at the engine oil inlet