Lubrication Systems Flashcards
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.
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.
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.
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 temperatures as well as the rotational speed.
Why do aircraft reciprocating engines use a relatively high viscosity oil?
Because they usually have larger operating clearances, and operate at high temperatures and pressures.
Name some oil contaminants.
Metal particles, dirt, carbon, moisture, and acids.
What is a possible indication of low oil pressure together with high oil temperature?
A low or inadequate oil supply.
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.
Why do oil reservoirs have expansion space?
To provide for oil foaming, thermal expansion, and air in the return oil.
What could cause oil foaming?
Diluted oil, contaminated oil, and the oil level being to high.
What controls oil pressure in a gear-type oil pressure pump?
An oil pressure relief valve.
What functions does an oil cooler bypass perform.
It directs the oil either through the cooler or around it in order to maintain the proper operating oil temperatures.
What could be a possible indication if the oil cooler passage becomes obstructed?
A high oil temperature.
Where is the oil temperature bulb usually located?
At the engine oil inlet.
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.
