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Module 15 > 15.10 > Flashcards

15.10 Flashcards

1
Q

Where does the lubrication system distribute oil to?

A

Engine bearings
Gearbox

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2
Q

What is the difference between wet and dry sumps?

A

The dry sump stores the oil in an external tank mounted on/near the engine

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3
Q

What do the wet and dry sumps do?

A

Recirculate the air whilst maintaining a constant pressure

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4
Q

What can the oil/lubrication system be divided into?

A

Full-flow and Constant pressure

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5
Q

What system has no way of regulation the oil pressure?

A

Full flow

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6
Q

In a full flow oil system, what does the oil pressure change with considering it has no means of being regulated?

A

N2 rotor speed (RPM and engine speed), The oil temperature and the flow areas downstream of the supply pump.

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7
Q

What rotor system is the supply pump driven by?

A

N2 via the gearbox

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8
Q

What happens as the N2 rotor speed increases?

A

There is higher flow so higher pressure oil

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9
Q

An increase of oil temperature leads to what sort of viscosity?

A

Lower viscosity

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10
Q

What does a decrease in oil temperature mean for the pressure?

A

Decreases

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11
Q

How can you detect a leakage in the oil system?

A

An increase in total flow area leading to a decrease in oil pressure

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12
Q

What happens if the leak is external?

A

A decrease in oil quantity and pressure (needs to move faster to compensate for quantity)

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13
Q

What prevents oil pressure from becoming too high?

A

Pressure relief valve

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14
Q

Where is the pressure relief valve installed in full flow?

A

Between delivery side and suction side

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15
Q

What is the constant pressure system also called?

A

The regulated pressure system

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16
Q

What does the constant pressure system have that the full flow system doesn’t?

A

Pressure regulating valve

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17
Q

What does the pressure regulating valve do in the constant pressure system?

A

It holds the pressure to a given value no matter the N2 rotor speed

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18
Q

FOR YOUR KNOWLEDGE, how does a full flow system work?

A

It reaches max pressure at idle then if it needs to exceed that, it will go beyond this making it inefficient

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19
Q

FOR YOUR KNOWLEDGE, how does a constant flow system work?

A

It reaches max pressure at idle and stays at this pressure even if the power is increased via speed via the N2 compressor

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20
Q

What is the purpose of the fuel systems discussed?

A

To deliver fuel to the nozzles

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21
Q

In what system do changes in the oil pressure have no effect on temperature?

A

Constant flow

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22
Q

What (in a constant flow unit) ensures that we have the same pressure regardless of engine speeds?

A

Pressure regulating system holding the pressure between the vent and the oil pressure

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23
Q

Why is the full flow system the most commonly used system?

A

It is simple and no adjustments are necessary

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24
Q

What are the two disadvantages of the full flow system?

A

System needs a large supply pump or relatively high oil pressure when the engines are at idle (leading to high oil pressure at high speeds.)

There is a significant increase in oil temperature after a power reduction (low flow rate)

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25
Q

What two types of cooling can engines use?

A

Air cooling
Oil cooling

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26
Q

Where is the air taken from for air cooling?

A

Early stages of compressor

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27
Q

What 3 things can air cooling be used to cool?

A

Turbine disc
Vanes
Blades

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27
Q

What does the oil require for lubrication?

A

An oil cooler

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28
Q

What does the use of cooling air reduce?

A

The quantity of oil to cool the bearings

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29
Q

What are the 4 subsystems that the basic lubrication system has?

A

Reservoir
Scavenge
Vent
Monitering

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30
Q

What is the purpose of the engine oil system?

A

To lubricate, cool and clean the bearing and gearboxes in the engine

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31
Q

What does system have the capability of doing to prevent ice formation in fuel?

A

Heat the engine fuel

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32
Q

What re the 3 subsystems of an oil system?

A

Storage
Distribution
Indicating

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33
Q

What is the oil tank made from?

A

Aluminium alloy with a silicone layer

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34
Q

What is the purpose of the silicone layer?

A

Fire resistance

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35
Q

What are the 2 ways to fill the tank?

A

Gravity
Pressure

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36
Q

How is gravity fill done?

A

Oil is added to the tank directly through the oil tank filler

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37
Q

How is pressure fill done?

A

Using a pressurised oil source connected to a filling manifold

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38
Q

The scupper (which surrounds the filler) has what purpose?

A

Catches spilled oil and drains it at the engine drain mast

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39
Q

What does a check valve prevent?

A

The discharge of air and oil when the cap is not correctly fitted

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40
Q

Where is the strainer and check valve located?

A

Bellow the filler cap

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41
Q

What is the purpose of the strainer?

A

Catches any large foreign particles during servicing

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42
Q

What is beneficial about the strainer for maintenance personnel?

A

Oil samples can be taken

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43
Q

What can you check the oil quantity with, that is positioned on the side face of the tank?

A

The sight glass

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44
Q

What is the primary source of oil cooling?

A

The fuel cooled oil cooler

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45
Q

How does the fuel cooled oil cooler work?

A

The oil cools as it heats the fuel

46
Q

What operates when additional oil cooling is required?

A

Air oil heat exchanger

47
Q

What is the single function of some oil pumps?

A

To supply or scavenge

48
Q

What are the 2 most common oil pumps?

A

Gerotor
Gear

49
Q

What are the 2 elements of the gear type pump?

A

Pressure
Scavenging

50
Q

Some pumps have several elements, how are they configured?

A

1 or more elements of pressure and 2 or more for scavenging

51
Q

How many elements does the gerotor pump contain?

A

2 (same as gear type)

52
Q

How can the capacity of the elements be controlled?

A

By varying the size of the gerotor elements

53
Q

Are each of the elements (pressure and scavenge) different or identical?

A

Identical

54
Q

Where is an oil pressure regulating valve incorporated into the oil system?

A

On the pressure side

55
Q

When is a pressure relief valve more of a pressure regulating valve?

A

When pressure in the system is kept in certain limits

56
Q

When would a large turbofan oil system not have a regulating valve?

A

Because the system varies with rpm and engine speed

57
Q

When is a relief valve especially important?

A

When oil coolers are involved because they are thin walls and easily ruptured

58
Q

When is a bypass valve included in an oil system?

A

When an oil cooler is involved

59
Q

What is the purpose of the bypass valve?

A

To maintain proper oil temperature and pressure

60
Q

What 2 things does the bypass valve vary the proportion of oil flow passing through?

A

The oil cooler and the filter

61
Q

What are screens in the suction lines used to protect?

A

Oil pumps

62
Q

When would lubrication system screens protect the oil nozzles?

A

If the supply filter is bypassed (called the last chance filter) they are upstream of the oil nozzles

63
Q

What 4 things do filters have in terms of construction?

A

A filter housing
Removable cover
Bypass valve
Clogging indicators

64
Q

When is the system called the hot tank system?

A

If the oil cooler/ heat exchanger is installed in the supply line

65
Q

Why is it called the hot tank system?

A

Because the oil is not cooled before entering the oil tank

66
Q

When is the system called a cold tank system?

A

When the oil cooler is installed in the scavenge line

67
Q

Why is it called a cold tank system?

A

Because the oil is called before it returns to the tank

68
Q

What are the 2 mains types of oil coolers?

A

Fuel cooled
Air cooled

69
Q

What are the advantages of fuel cooled oil coolers?

A

They are efficient and small

70
Q

What aircraft are air cooled oil coolers used on?

A

Turboprop engines and APUs

71
Q

What are the main components of a typical fuel cooled oil cooler?

A

Housing
Cover
Core

72
Q

How many scavenge pumps are there?

A

7

73
Q

What is the purpose of the scavenge pumps?

A

To remove oil from the bearings and gearboxes

74
Q

What is in the external gearbox that removes air overboard from the scavenge oil?

A

A breather

75
Q

Where is a de-aerator installed?

A

At the inlet for the scavenge wheel

76
Q

What is the purpose of the de-aerator?

A

Separates air from incoming scavenge oil

77
Q

What does the air leave the oil tank via?

A

The vent line

78
Q

What can happen if the tank filler cap is removed during present HP air?

A

Hot oil can spill out the tank

79
Q

How long is the HP air present for after engine shutdown?

A

5 mins

80
Q

What does the oil indication monitor?

A

Quantity
Condition
Pressure
Temperature

81
Q

What are the 2 types of transmitters used for indication?

A

Capacitance type
Reed switch type

82
Q

What is the principle of the capacitive level measurement based on?

A

The capacitance change of the capacitor

83
Q

What is the upper and lower of the capacitance transmitter?

A

The upper part has electronic components for a capacitance measurement (measuring the capacity) and the lower part is immersed in oil and has 2 concentric tubes

84
Q

What does the Reed type transmitter consist of?

A

A metal tube with a float inside and a multi switch assembly

85
Q

What activates the internal switch assembly?

A

Permanent magnets

86
Q

When the tank is full, where is the float?

A

The upper limits

87
Q

What changes with the switch?

A

Resistance

88
Q

What do oils contain to boost their performance?

A

Additives

89
Q

What does SOAP stand for?

A

Spectrometric
Oil
Analysis
Program

90
Q

Where does the engine oil carry particles from the bearings and the gears to?

A

Filters and the lubrication system

91
Q

What is monitored by the debris monitoring system?

A

The quantity, size and type of material for indication of internal wear of lubricated parts

92
Q

What size particles does a scavenge oil filter element catch?

A

more than 0.0015

93
Q

What happens to the particles caught in the filter?

A

They are removed and sent for testing

94
Q

What size particles can SOAP analysis find?

A

0.001-0.02mm (so small they cannot be caught in normal oil filters)

95
Q

What is the disadvantage of SOAP?

A

Filter element is not changed often, but when it is it takes time

96
Q

When are SOAP samples taken periosdically?

A

When the engines are shut down

96
Q
A
96
Q

Where are oil samples for SOAP taken from?

A

The oil tank

97
Q

What is an advantage of magnetic chips?

A

Theyre less time consuming
Easier

98
Q

What do magnetic chip detectors a catch?

A

Metal particles that are attracted to the magnet

99
Q

How are magnetic chip detectors checked?

A

Manually and on some aircraft they are electronically monitored

100
Q

What happens to resistance when particles connect to the magnet?

A

It decreases

101
Q

What is the resistance between the two chip detector magnets monitored by?

A

The electric control unit (ECU)

102
Q

Where can the oil quantity be checked at?

A

Sight gages or ECAM/EICAS

103
Q

What does the siphoning effect do to the flow of oil from the tank to the gearbox?

A

Makes it slower

104
Q

What is installed to prevent the siphoning effect on a oil system?

A

An anti-siphon device

105
Q

On engines without anti-siphon what is the time interval after engine shut-down that you can check the oil quantity in the tank?

A

Between 5 and 20 minuets

106
Q

How long should you wait before opening the oil tank filler cap?

A

5 minuets

107
Q

If you can smell fuel when opening the filler cap, where is a leakage indicated?

A

In the fuel cooled oil cooler

108
Q

What 2 things can the oil system be replenished using?

A

Oil cans (gravity)
Oil servicing (pressure)

109
Q

Where can details of the required oil type be found?

A

On a label close to the oil tank filler cap

110
Q

Because monitoring the oil consumption of the engine is important, what must you enter into the logbook?

A

Quantity of oil added to the tank

Module 15 (18 decks)

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