Chapter 9 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.
What are the functions of lubricating oil in reciprocating engines?
To reduce friction between moving parts and remove heat.
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 temperature as well as rotational speed.
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.
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 up 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 too high.
What controls oil pressure in a gear type oil pressure pump?
An oil pressure relief valve.
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.
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.
