Jeppesen Chapter 9 - Lubrication Systems (22 items)

Question 1

Q1. A reciprocating engine is found to have excessive oil consumption without evidence of any oil leaks. What is the likely cause?

Answer 1

A1. The piston rings are worn or broken.

Question 2

Q3. Name two important characteristics of aircraft engine oil.

Answer 2

A3. The oil must be light enough to circulate freely yet heavy enough to provide the proper oil film at engine operating temperatures.

Question 3

Q4. What could happen to an oil that is too low in viscosity at normal engine operating temperatures?

Answer 3

A4. It may become so thin that the oil film between moving parts is easily broken, resulting in premature wear.

Question 4

Q5. 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

A5. The operating load and temperatures as well as the rotational speed.

Question 5

Q6. Why do aircraft reciprocating engines use a relatively high viscosity oil?

Answer 5

A6. Because they usually have larger operating clearances, and operate at high temperatures and pressures.

Question 6

Q7. Name some oil contaminants.

Answer 6

A7. Metal particles, dirt, carbon, moisture, and acids.

Question 7

Q8. What is a possible indication of low oil pressure together with high oil temperature?

Answer 7

A8. A low or inadequate oil supply.

Question 8

Q9. 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 of harmful deposits, and the inside of the engine clean.

Question 9

Q10. Why do oil reservoirs have expansion space?

Answer 9

A10. To provide for oil foaming, thermal expansion, and air in the return oil.

Question 10

Q11. What could cause oil foaming?

Answer 10

A11. Diluted oil, contaminated oil, and the oil level being to high.

Question 11

Q12. What controls oil pressure in a gear-type oil pressure pump?

Answer 11

A12. An oil pressure relief valve.

Question 12

Q13. What functions does an oil cooler bypass perform.

Answer 12

A13. It directs the oil either through the cooler or around it in order to maintain the proper operating oil temperatures.

Question 13

Q14. What could be a possible indication if the oil cooler passage becomes obstructed?

Answer 13

A14. A high oil temperature.

Question 14

Q15. Where is the oil temperature bulb usually located?

Answer 14

A15. At the engine oil inlet.

Question 15

Q16. What does the presence of metal particles in an engine oil filter indicate?

Answer 15

A16. Depending on the type and size of the metal particles, this usually indicates abnormal wear and possible engine internal failure.

Question 16

Q17. What should be done if metal particles are found in an engine oil filter?

Answer 16

A17. Follow engine manufacture’s maintenance instructions.

Question 17

Q18. Where is the most critical point of lubrication in a gas turbine engine?

Answer 17

A18. At the turbine bearing.

Question 18

Q19. What type of oil is used in a turbine engine oil system?

Answer 18

A19. Synthetic oil.

Question 19

Q20. Where are oil screens or filters most likely located in a turbine engine oil system?

Answer 19

A20. At the oil pressure system (main filter), scavenge system, and at or just before the oil jet (last chance).

Question 20

Q21. Name two types of turbine engine oil coolers.

Answer 20

A21. Air cooled and fuel cooled.

Question 21

Q22. What could happen to an oil that is too low in viscosity at normal engine operating temperatures?

Answer 21

A22. It may become so thin that oil film between the moving parts is easily broken resulting in premature wear.

Question 22

Q2. What are the functions of lubricating oil in reciprocating engines?

Answer 22

A2. To reduce friction between moving parts and remove heat.