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

The piston rings are worn or broken. (Page Reference: JSPT 9-3)

What are the functions of lubricating oil in reciprocating engines?

To reduce friction between moving parts and remove heat. (Page Reference: JSPT 9-2)

Name two important characteristics of aircraft engine oil?

The oil must be light enough to circulate freely yet heavy enough to provide the proper oil film at engine operating temperatures. (Page Reference: JSPT 9-2)

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

It may become so thin that the oil film between moving parts is easily broken, resulting in premature wear. (Page Reference: JSPT 9-3)

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?

The operating load and temperature as well as the rotational speed. (Page Reference: JSPT 9-3)

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

Because they usually have large operating clearances, and operate at high temperatures and pressures. (Page Reference: JSPT 9-3)

Name some oil contaminants.

Metal particles, dirt, carbon, moisture and acids. (Page Reference: JSPT 9-3)

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

A low or inadequate oil supply. (Page Reference: JSPT 9-20)

In ashless dispersant (AD) oils, what function does the dispersant perform?

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. (Page Reference: JSPT 9-5)

Why do oil reservoirs have expansion space?

To provide for oil foaming, thermal expansion, and air in the return oil. (Page Reference: JSPT 9-9)

What could cause oil foaming?

Diluted oil, contaminated oil, and the oil level being too high. (Page Reference: JSPT 9-13)

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

An oil pressure relief valve. (Page Reference: JSPT 9-13)

What function does an oil cooler bypass valve perform?

It directs the oil either through the cooler or around it in order to maintain proper operating oil temperatures. (Page Reference: JSPT 9-18)

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

A high oil temperature. (Page Reference: JSPT 4-18)

Where is the oil temperature bulb usually located?

At the engine oil inlet. (Page Reference: JSPT 9-20)

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

Depending on the type and size of the metal particles, this usually indicates abnormal wear and possible engine internal failure. (Page Reference: JSPT 9-21)

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

Follow engine manufacturer's maintenance instruction. (Page Reference: JSPT 9-21)

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

At the turbine bearing. (Page Reference: JSPT 9-33)

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

Synthetic oil. (Page Reference: JSPT 9-27)

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

At the oil pressure system (main filter), scavenge system, and at or just before the oil jet (last chance). (Page Reference: JSPT 9-31)

Name two types of turbine engine oil coolers.

Air cooled and fuel cooled. (Page Reference: JSPT 9-33)

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

It may become so thin that the oil film between moving parts is easily broken resulting in premature wear. (Page Reference: JSPT 9-3)