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M15 > 15.14 Engine Indication Systems > Flashcards

15.14 Engine Indication Systems Flashcards

1
Q

What are the 2 relevant temperatures of the engine?

A

Exhaust Gas Temperature (EGT)

Turbine Inlet Temperature (TIT)

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2
Q

Why are EGT measured?

A

To prevent thermal damage.

Indicate if a limit is exceeded.

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3
Q

Where is EGT measured?

A

At a colder location between HPT and LPT or directly behind LPT.

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4
Q

What is TIT?

A

The highest temperature directly behind combustion chamber.

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5
Q

What temperature is physically measured.

A

Only EGT, TIT is calculated using EGT.

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6
Q

How does an EGT indicator show average temp?

A

Using individual thermocouples.

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7
Q

What is the scale range of an EGT indicator?

A

0-1200 C

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8
Q

What happens when TIT is high?

A

An over temp warning light will illuminate.

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9
Q

What are engine thrust indications divided into?

A

Performance/ primary.
System/secondary.
Engine trend maintenance.

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10
Q

As Thrust can’t be measured directly, what are the 2 indications of equivalent value?

A

Engine Pressure Ratio (EPR).
N1 (fan) speed.

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11
Q

What is the purpose of system indication?

A

To monitor correct system operation.

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12
Q

When is engine trend monitoring done?

A

On ground to detect engine problems.

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13
Q

What 3 analyses are done for trend monitoring?

A

Thermodynamic,
Mechanic dynamic,
Oil consumption.

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14
Q

What is EPR?

A

A measured of thrust being developed.

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15
Q

How is EPR measured?

A

Comparing RAM air at engine inlet and exhaust.

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16
Q

What does a AMBER + RED indication mean on an EPR display?

A

Maximum thrust available.

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17
Q

What does the blue circle indicator on the EPR display mean?

A

It corresponds to the actual throttle position.

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18
Q

What is Flexible take off?

A

The standard take off thrust.

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19
Q

What do Boeing call Flexible take off?

A

Assumed temperature derate.

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20
Q

What does oil pressure indicate?

A

The pressure of engine oil pump discharge.

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21
Q

What are the 2 oil pressure indicator types?

A

Bourden tube.

Strain gauge.

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22
Q

The strain gauge indicator uses what configuration?

A

Wheatstone bridge configuration.

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23
Q

What principle does a strain gauge indicator use?

A

Strain causes a proportional resistance change.

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24
Q

What is the low oil pressure switch connected to?

A

Oil supply line and oil tank vent line.

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25
Q

Where is a low oil pressure switch connected to?

A

Flight warning computer.

26
Q

What does an oil temperature sensor use?

A

Resistance Temperature Detector (RTD)
Thermocouples.

27
Q

Where is oil temperature measured?

A

At the oil pump entrance.

28
Q

What does an over temperature warning produce?

A

A visual and audible warning.

29
Q

Where is the low pressure sensor located?

A

At the LP filter outlet.

30
Q

Where is a differential pressure sensor fitted?

A

Across the filter.

31
Q

What do light reciprocating engine aircraft use to measure fuel pressure?

A

A direct reading Bourden tube pressure gauge.

32
Q

Where is the fuel pressure gauge connected?

A

To the inlet of the fuel metering device.

33
Q

What does a pressure warning signal produce?

A

It illuminates a warning light using simple pressure sensing switches and an audible warning.

34
Q

What 2 indications are used to measure fuel flow?

A

Actual fuel flow to engine,
Fuel used since engine was started.

35
Q

What is fuel indicated in?

A

Weight.
Kg, tons, lbs.

36
Q

What is fuel flow calculated by?

A

The FADEC system.

37
Q

What does a fuel flow transmitter measure and where?

A

Mass flow between FCU and fuel nozzles.

38
Q

What are the 2 fuel flow transmitters used?

A

Synchronous mass flow.
Motorless mass flow.

39
Q

What do the impeller, motor and turbine do in a synchronous mass flow transmitter?

A

Impeller turns with the electric motor.

Motor accelerates fuel through the transmitter.

Turbine measures deflection angle against a spring.

40
Q

How does a motorless mass flow transmitter accelerate fuel?

A

Using the fuel itself and a small turbine.

41
Q

How is the deflection angle measured in a motorless mass flow transmitter?

A

Using 2 coils in combination with 4 permanent magnets.

42
Q

How can turbine engine speed be measured?

A

Variable reluctance sensor = measures N1

Tachometer generator type = measures N2

43
Q

How does a variable reluctance sensor measure turbine engine speed?

A

By detecting a change in magnetic flux.

44
Q

In a variable reluctance sensor, a speed probe is positioned on compressor casing in line with what?

A

A phonic wheel or actual fan blades.

45
Q

What makes up a tachometer generator ?

A

A permanent magnet driven by a gearbox.

46
Q

What does the permanent magnet do in a tachometer generator?

A

It generates 3 phases AC voltage with a frequency that is proportional to speed input.

47
Q

What is another purpose of the Permanent Magnet Generator?

A

It also tells the pilot ether the engine is turning in the correct direction.

48
Q

What are the 3 types of rotor speed indicators?

A

Clock type.
Moving vertical bar.
Electromechanical.

49
Q

What is vibration measured in?

A

Units from 0 to 6.

50
Q

What is the vibration monitoring computer called?

A

Engine Vibration Monitoring Unit (EVMU)

51
Q

What does an accelerometer measure?

A

Radial acceleration of rotor system.

52
Q

Where are the 2 accelerometers located?

A

In the compressor area and in the turbine area.

53
Q

What are the 2 types of accelerometers?

A

Electromagnetic
Piezoelectric crystal.

54
Q

How does the piezoelectric crystal accelerometer work?

A

It generates a voltage when a force is applied to the crystal.

55
Q

In vibration indication, if a speed signal fails, what does rotor identification show?

A

Broadband (BB) vibration.

56
Q

What are the 2 types of torque meters?

A

Electric or hydraulic.

57
Q

How does an electric torque meter work?

A

A twist in the shaft is measured by the difference between 2 shafts.

58
Q

How does a hydraulic torque meter work?

A

A helical gear moves in response to applied torque.

59
Q

What is a critical power test?

A

A power assurance test.

60
Q

What does a power assurance test check?

A

If the engine can accelerate to Engine Pressure Ratio in a specific time and decelerate in a specific time.

61
Q

How long must an engine operate at idle for before a power assurance test?

A

5 mins.

62
Q

After what conditions must the engine be left to cool down and for how long?

A

After operation for 8s above 70% power.
Leave for 10 mins.

M15 (18 decks)

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