Lubrication Systems

Question 1

A reciprocating engine is found to have excessive oil consumption without evidence of any oil leaks, what is the likely cause?

Answer 1

The piston rings are worn or broken

Question 1

What are the functions of lubricating oil in a reciprocating engine?

Answer 1

To reduce friction between moving parts and remove heat

Question 2

Name two important characteristics of aircraft engine oil

Answer 2

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

Question 3

What could happen to an oil that is too low in viscosity at normal engine operating temperatures?

Answer 3

It may become so thin that the oil film that is between moving parts is easily broken, resulting in premature wear

Question 4

What are some of the factors that must be considered by an engine manufacturer in determining the proper grade of oil for a particular engine?

Answer 4

The operating load and temperature as well as the rotational speed

Question 5

Name some oil contaminants

Answer 5

Metal particles, dirt, carbon, moisture and acids

Question 6

Why do aircraft reciprocating engines use relatively high viscosity oil?

Answer 6

Because they usually have large operating clearances and operate at high temperatures and pressures

Question 7

What is a possible indication of low oil pressure together with high oil temperature?

Answer 7

A low or inadequate oil supply

Question 8

In ashless dispersant ad oils, what function does the dispersant perform?

Answer 8

The dispersant causes sludge forming materials to repel each other and remain in suspension until they can be trapped by the oil filter or drained. This keeps the oil passages and ring grooves free from harmful deposits and the inside of the engine clean

Question 9

Why do oil reservoirs have expansion space?

Answer 9

To provide for oil foaming, thermal expansion and air in the returned oil

Question 10

What could cause oil foaming?

Answer 10

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

Question 11

What controls oil pressure in a gear type oil pressure pump?

Answer 11

An oil pressure relief valve

Question 12

What function does an oil cooler bypass valve perform?

Answer 12

It directs the oil either through the cooler or around it in order to perform proper operating oil temperatures

Question 13

What could be a possible indication if the oil cooler passage becomes obstructed?

Answer 13

A high oil temperature

Question 14

Where is the oil temperature bulb usually located?

Answer 14

At the engine oil inlet

Question 15

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

Answer 15

Depending on the type and size of the metal particles, this usually indicates abnormal wear and possible engine internal failure

Question 16

What should be done if metal particles are found in the engine oil filter?

Answer 16

Follow the engine manufacturer’s maintenance instructions

Question 17

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

Answer 17

At the turbine bearing

Question 18

What type of oil is used in a turbine engine oil system?

Answer 18

Synthetic oil

Question 19

Where are oil screens or filters most likely located in a turbine engine oil system?

Answer 19

At the oil pressure system, main filter, scavenge system and at or just before the oil jet

Question 20

Name two types of turbine engine oil coolers

Answer 20

Air cooled and fuel cooled