Questions - Aircraft Powerplant Lubrication Systems

Fill in the Blanks

1. The resistance of an oil to flow is known as its __________.

2. The measure of the change in __________ of oil with a given change in temperature is known as the __________ index.

3. The point at which a liquid will begin to give off ignitable vapors is known as the __________ point.

4. If incompatible oil has been added to a turbine engine, it is often necessary to __________ and __________ the oil system before refilling with the proper oil.

5. Oil tanks used on engines equipped with Hydromatic propellers will feed the pressure pump from a standpipe, leaving a reserve of oil for __________.

6. The __________ valve determines which of the two possible paths the oil will take through a cooler.

7. __________ is a system installed on some reciprocating engines to aid in cold weather starting by introducing fuel into the oil system prior to shutdown.

8. Oil pressure is measured at the __________ of the engine driven oil pump.

9. Oil coolers are normally removed and thoroughly cleaned and inspected at __________ (what event).

10. Oil consumption in turbine engines is __________ than that in reciprocating engines.

11. Turbine engine oil tanks must have an expansion space of __________ % or 0.5 gallon, whichever is greater.

12. Fine mesh screens called __________ filters strain the oil just before it is sprayed onto the bearing surfaces of a turbine engine.

13. Check valves in the oil supply lines prevent accumulations of oil in the __________ of the engine while the engine is not operating.

14. If turbine oil is observed to be dark brown or blackish with little or no contaminants present, it is probably caused by a chemical reaction to __________.

15. Magnetic chip detectors are usually found in the __________ subsystem of a gas turbine engine.


1. An engine lubricating oil whose viscosity changes very little for a given change in temperature has a low viscosity index. TRUE/FALSE

2. The lubricating properties of straight mineral oil are as good as those of ashless dispersant oil. TRUE/FALSE

3. Synthetic lubricating oils are multi- viscosity oils. TRUE/FALSE

4. Turbine engine oils do use a standard identification system. TRUE/FALSE

5. SAE numbers are not used to identify turbine oils. TRUE/FALSE

6. The scavenge subsystem will have a greater capacity than the pressure subsystem. TRUE/FALSE

7. Magnetic chip detectors are usually found in the pressure subsystem of a gas turbine engine. TRUE/FALSE

8. The Electric Pulsed Chip Detector cannot discriminate between small wear particles and larger particles. TRUE/FALSE

9. Most oil temperature bulbs are mounted in the pressure oil screen housing. TRUE/FALSE

10. The oil cooler used with this aircraft’s opposed-type engine is the honeycomb type. TRUE/FALSE

Knowledge Application Questions

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

2. Name two important characteristics of aircraft engine oil.

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

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?

5. Why do oil reservoirs have expansion space?

6. What could cause oil foaming?

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

8. What function does an oil cooler bypass valve perform?

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

10. Where is the oil temperature bulb usually located?

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

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

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

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

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

Multiple Choices Questions

1. What will be the result of operating an engine in extremely high temperatures using a lubricant recommended by the manufacturer for a much lower temperature?
a. The oil pressure will be higher than normal.
b. The oil temperature and oil pressure will be higher than normal.
c. The oil pressure will be lower than normal.

2. (1) Gas turbine and reciprocating engine oils can be mixed or used interchangeably.
(2) Most gas turbine engine oils are synthetic.

Regarding the above statements,
a. only No. 2 is true.
b. both No. 1 and No. 2 are true.
c. neither No.1 nor No. 2 is true.

3. An oil separator is generally associated with which of the following?
a. Engine-driven oil pressure pump.
b. Engine-driven vacuum pump.
c. Cuno oil filter.

4. The time in seconds required for exactly 60 cubic centimeters of oil to flow through an accurately calibrated orifice at a specific temperature is recorded as a measurement of the oil's
a. flash point.
b. specific gravity.
c. viscosity.

5. Upon what quality or characteristic of a lubricating oil is its viscosity index based?
a. Its resistance to flow at a standard temperature as compared to high grade paraffin-base oil at the same temperature.
b. Its rate of change in viscosity with temperature change.
c. Its rate of flow through an orifice at a standard temperature.

6. Lubricating oils with high viscosity index ratings are oils
a. in which the viscosity does not vary much with temperature change.
b. in which the viscosity varies considerably with temperature change.
c. which have high SAE numbers.

7. Compared to reciprocating engine oils, the types of oils used in turbine engines
a. are required to carry and disperse a higher level of combustion by-products.
b. may permit a somewhat higher level of carbon formation in the engine.
c. have less tendency to produce lacquer or coke.

8. The oil used in reciprocating engines has a relatively high viscosity due to
a. the reduced ability of thin oils to maintain adequate film strength at altitude. (reduced atmospheric pressure).
b. the relatively high rotational speeds.
c. large clearances and high operating temperatures.

9. If all other requirements can be met, what type of oil should be used to achieve theoretically perfect engine lubrication?
a. The thinnest oil that will stay in place and maintain a reasonable film strength.
b. An oil that combines high viscosity and low demulsibility.
c. An oil that combines a low viscosity index and a high neutralization number.

10. In addition to lubricating (reducing friction between moving parts), engine oil performs what functions?
I. Cools.
2. Seals.
3. Cleans.
4. Prevents corrosion.
5. Cushions impact (shock) loads.

a. 1, 2, 3, 4
b. 1, 2, 3, 4, 5
c. 1, 3, 4

11. Which of these characteristics is desirable in turbine engine oil?
a. Low flash point.
b. High flash point.
c. High volatility.

12. The viscosity of a liquid i s a measure of its
a. resistance to flow.
b. rate of change of internal friction with change in temperature.
c. weight or density.

13. What type of oil system is usually found on turbine engines?
a. Dry sump, pressure, and spray.
b. Dry sump, dip, and splash.
c. Wet sump, spray, and splash.

14. Which of the following factors helps determine the proper grade of oil to use in a particular engine?
a. Adequate lubrication in various attitudes of flight.
b. Positive introduction of oil to the bearings.
c. Operating speeds of bearings.

15. Specific gravity i s a comparison of the weight of a substance to the weight of an equal volume of
a. oil at a specific temperature.
b. distilled water at a specific temperature.
c. mercury at a specific temperature.

16. Oil tank fillers on reciprocating engines are marked with the word
a. "oil," and tank capacity, in accordance with 14 CFR part 45.
b. "oil," type, and grade, in accordance with 14 CFR part 33.
c. "oil," in accordance with 14 CFR part 23.

17. What advantage do mineral base lubricants have over vegetable oil base lubricants when used in aircraft engines?
a. Cooling ability.
b. Chemical stability.
c. Friction resistance.

18. The recommended aircraft engine lubricants are
a. mineral or synthetic based.
b. vegetable, mineral, or synthetic based.
c. animal, mineral, or synthetic based.

19. High tooth pressures and high rubbing velocities, such as occur with spur-type gears, require the use of
a. an EP lubricant.
b. straight mineral oil.
c. metallic ash detergent oil.

20. Manufacturers normally require turbine engine oil servicing within a short time after engine shutdown primarily to
a. prevent overservicing.
b. help dilute and neutralize any contaminants that may already be present in the engine's oil system.
c. provide a better indication of any oil leaks in the system.

21. What type of oil do most engine manufacturers recommend for new reciprocating engine break-in?
a. Ashless-dispersant oil.
b. Straight mineral oil.
c. Semi-synthetic oil.

22. What type of oil do most engine manufacturers recommend after new reciprocating engine break-in?
a. Metallic-ash detergent oil.
b. Ashless-dispersant oil.
c. Straight mineral oil.

23. The type of oil pumps most commonly used on turbine engines are classified as
a. positive displacement.
b. variable displacement.
c. constant speed.

24. As a general rule, the mixture setting on a reciprocating engine operating at or near takeoff power that provides the best cooling is
b. LEAN.

25. The engine oil temperature regulator is usually located between which of the following on a dry sump reciprocating engine?
a. The engine oil supply pump and the internal lubrication system.
b. The scavenger pump outlet and the oil storage tank.
c. The oil storage tank and the engine oil supply pump.

26. What will happen to the return oil if the oil line between the scavenger pump and the oil cooler separates?
a. Oil will accumulate in the engine.
b. The return oil will be pumped overboard.
c. The scavenger return line check valve will close and force the oil to bypass directly to the intake side of the pressure pump.

27. At cruise RPM, some oil will flow through the relief valve of a gear-type engine oil pump. This is normal as the relief valve is set at a pressure which is
a. lower than the pump inlet pressure.
b. lower than the pressure pump capabilities.
c. higher than pressure pump capabilities.

28. (1) Fuel may be used to cool oil in gas turbine engines.
(2) Ram air may be used to cool oil in gas turbine engines.

Regarding the above statements,
a. only No. 1 is true.
b. only No. 2 is true.
c. both No. 1 and No. 2 are true.

29. In a reciprocating engine oil system, the temperature bulb senses oil temperature
a. at a point after the oil has passed through the oil cooler.
b. while the oil is in the hottest area of the engine.
c. immediately before the oil enters the oil cooler.

30. The oil dampened main bearing utilized in some turbine engines is used to
a. provide lubrication of bearings from the beginning of starting rotation until normal oil pressure is established.
b. provide an oil film between the outer race and the bearing housing in order to reduce vibration tendencies in the rotor system, and to allow for slight misalignment.
c. dampen surges in oil pressure to the bearings.

31. What is the purpose of the last chance oil filters?
a. To prevent damage to the oil spray nozzle.
b. To filter the oil immediately before it enters the main bearings.
c. To assure a clean supply of oil to the lubrication system.

32. In a jet engine which uses a fuel-oil heat exchanger, the oil temperature is controlled by a thermostatic valve that regulates the flow of
a. fuel through the heat exchanger.
b.- both fuel and oil through the heat exchanger.
c. oil through the heat exchanger.

33. What prevents pressure within the lubricating oil tank from rising above or falling below ambient pressure (reciprocating engine)?
a. Oil tank check valve.
b. Oil pressure relief valve.
c. Oil tank vent.

34. In an axial-flow turbine engine, compressor bleed air is sometimes used to aid in cooling the
a. fuel.
b. inlet guide vanes.
c. turbine, vanes, blades, and bearings.

35. Oil picks up the most heat from which of the following turbine engine components?
a. Rotor coupling.
b. Compressor bearing.
c. Turbine bearing.

36. Which of the following is a function of the fuel-oil heat exchanger on a turbojet engine?
a. Aerates the fuel.
b. Emulsifies the oil.
c. Increases fuel temperature.

37. According to Federal Aviation Regulations (FAR'S), oil tank fillers on turbine engines must be marked with the word
a. "oil" and the type and grade of oil specified by the manufacturer.
b. "oil" and tank capacity.
c. "oil."

38. After making a welded repair to a pressurized-type turbine engine oil tank, the tank should be pressure checked to
a. not less than 5 PSI plus the maximum operating pressure of the tank.
b. not less than 5 PSI plus the average operating pressure of the tank.
c. 5 PSI.

39. Why are fixed orifice nozzles used in the lubrication system of gas turbine engines?
a. To provide a relatively constant oil flow to the main bearings at all engine speeds.
b. To keep back pressure on the oil pump, thus preventing an air lock.
c. To protect the oil seals by preventing excessive pressure from entering the bearing cavities.

40. Possible failure related ferrous-metal particles in turbine engine oil cause an (electrical) indicating-type magnetic chip detector to indicate their presence by
a. disturbing the magnetic lines of flux around the detector tip.
b. bridging the gap between the detector center (positive) electrode and the ground electrode.
c. generating a small electric current that is caused by the particles being in contact with the dissimilar metal of the detector tip.

41. What would be the probable result if the oil system pressure relief valve should stick in the open position on a turbine engine?
a. Increased oil pressure.
b. Decreased oil temperature.
c. Insufficient lubrication.

42. What is the primary purpose of the oil-to-fuel heat exchanger?
a. Cool the fuel.
b. Cool the oil.
c. De-aerate the oil.

43. What unit in an aircraft engine lubrication system is adjusted to maintain the desired system pressure?
a. Oil pressure relief valve.
b. Oil viscisity valve.
c. Oil pump.

44. Low oil pressure can be detrimental to the internal engine components. However, high oil pressure
a. should be limited to the engine manufacturer's recommendations.
b. has a negligible effect.
c. will not occur because of pressure losses around the bearings.

45. What is the primary purpose of the oil breather pressurization system that is used on turbine engines?
a. Prevents foaming of the oil.
b. Allows aeration of the oil for better lubrication because of the airloil mist.
c. Provides a proper oil spray pattern from the main bearing oil jets.

46. The purpose of directing bleed air to the outer turbine case on some engines is to
a. provide optimum turbine blade tip clearance by controlling thermal expansion.
b. provide up to 100 percent kinetic energy extraction from the flowing gases.
c. allow operation in a thermal environment 600 to 800 OF above the temperature limits of turbine blade and vane alloys.

47. Some larger reciprocating engines use a compensating oil pressure relief valve to
a. provide a high engine oil pressure when the oil is cold and automatically lower the oil pressure when the oil warms up.
b. compensate for changes in atmospheric pressure that accompany altitude changes.
c. automatically keep oil pressure nearly the same whether the oil is warm or cold.

48. In order to relieve excessive pump pressure in an engine's internal oil system, most engines are equipped with a
a. vent.
b. bypass valve.
c. relief valve.

49. What is the source of most of the heat that is absorbed by the lubricating oil in a reciprocating engine?
a. Crankshaft main bearings.
b. Exhaust valves.
c. Pistons and cylinder walls.

50. How are the teeth of the gears in the accessory section of an engine normally lubricated?
a. By splashed or sprayed oil.
b. By submerging the load-bearing portions in oil.
c. By surrounding the load-bearing portions with baffles or housings within which oil pressure can be maintained.
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