Engine Lubrication Systems

Question 1

What is straight mineral oil?

Answer 1

It is the lubricating oil as obtained by fractional distillation of crude oil. It does not have any additives.

Question 2

What is ashless dispersant (AD) oil?

Answer 2

A mineral lubricating oil containing additives that disperse the contaminants throughout the oil so they will not clump and clog oil passages. There are no ash-forming additives in AD oil.

Question 3

What is synthetic oil?

Answer 3

A lubricating oil that is mad by chemically changing the nature of an oil base to give it the needed characteristics. Synthetic oil is the primary oil for turbine engines.

Question 4

Is automotive oil suitable for use in aircraft engines?

Answer 4

No, automotive and aviation oils are formulated for entirely different operating conditions.

Question 5

What is meant by a multiviscosity oil?

Answer 5

It is a lubricating oil with a viscosity index improver that increases the viscosity of the oil when it is hot and decreases the viscosity when it is cold.

Question 6

Where can you find the grade of engine oil specified for a particular aircraft?

Answer 6

In the airplane flight manual or the pilot’s operating handbook for the aircraft.

Question 7

What are six functions of the oil in an aircraft engine?

Answer 7

-Reduces friction
-Seals and cushions
-Removes heat
-Cleans inside the engine
-Protects against corrosion
-Performs hydraulic action

Question 8

What is the purpose of an air-oil separator, or deaerator, in a turbine engine oil tank?

Answer 8

In normal operation, the oil picks up a quantity of air and it is swirled as it enters the deaerator. The swirling action releases the air from the oil, and the air is used to pressurize the oil tank.

Question 9

How is oil pressure regulated in an aircraft engine?

Answer 9

A pressure-relief valve senses the desired pressure and sends excess oil back into the engine sump.

Question 10

What is the purpose of the restricted orifice in the line between the oil pressure gauge and the engine?

Answer 10

The restricted fitting helps dampen any pulsations in the oil pressure cause by the pump.

Question 11

What is a hot-tank lubrication system for a turbojet engine?

Answer 11

a lubrication system in which the oil cooler is in the pressure subsystem and the scavenged oil is not cooled before it is returned to the tank.

Question 12

what is a cold-tank lubrication system for a turbojet engine?

Answer 12

A lubrication system in which the oil cooler is in the scavenge subsystem, and the scavenged oil is cooled before it is returned to the tank.

Question 13

Where does a wet sump oil system store oil?

Answer 13

In a reservoir inside the engine.

Question 14

Where does a dry sump oil system store oil?

Answer 14

In a reservoir outside the engine through the use of a scavenge pump and external tubing.

Question 15

What is the purpose of a chip detector?

Answer 15

Magnetic chip detectors are used in the oil system to detect and catch ferrous particles present in the oil. During maintenance, the chip detectors are removed from the engine and inspected for metal; if none is found, the detector is cleaned, replaced, and safety wired. If metal is found on a chip detector, an investigation should be made to find the source of the metal on the chip.

Question 16

What components in a reciprocating-engine lubrication system must be inspected on a 100-hour or annual inspection?

Answer 16

-The oil supe or tank
-Oil strainer screen
-Oil filter
-Oil cooler and the temperature control valve
-Oil pressure and temperature gauges and any transmitters associated with them
-The entire engine for indications of oil leaks

Question 17

What two instruments show the condition of a reciprocating-engine lubrication system?

Answer 17

-Oil pressure
-Oil temperature gauges.

Question 18

What must be done to an oil filter when it is removed from the engine?

Answer 18

It should be cut open and the pleated element examined to determine the type and amount of contaminant carried by the oil.

Question 19

What is a spectrometric oil analysis program?

Answer 19

A program in which a sample of oil is taken from the engine at regular intervals and sent to a laboratory, where it is burned in an electric arc. The resulting light is analyzed for the wavelengths of the elements that are present in the oil sample. Traces of aluminum, copper, and iron in the oil indicate wear of the pistons or wrist pin plugs (aluminum), cylinder walls or piston rings (iron), or main bearings or bushing (copper). A single sample is meaningless. There must be a series of samples taken at regular intervals to measure the change in the amounts of these metals.

Question 20

What type of oil quantity indicator is used in most aircraft engines?

Answer 20

A dipstick that measures the quantity of oil in the tank or sump.

Question 21

When should the engine oil quantity be checked on a turnine engine?

Answer 21

As soon as practical after the engine is shut down.

Question 22

Where is the oil temperature measured on a reciprocating engine?

Answer 22

Usually at the oil pressure screen before the oil goes into the engine passages.

Question 23

Why do engine manufacturers recommend that engine lubricating oil be changed at specific intervals?

Answer 23

The oil pick up contaminants and carries them through the engine where then can cause wear. The oil also becomes acidic and causes corrosion in the engine.

Question 24

What problem can improper piston ring conditioning (also known as run-in or break-in) lead to?

Answer 24

High oil consumption.

Question 25

What are causes of high oil consumption in a reciprocating engine?

Answer 25

-Failing or failed bearing
-Worn or broken piston rings
-Incorrect installation of piston rings
-External oil leakage
-Leakage through engine fuel pump vent
-Engine breather or vacuum pump breather