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Module 15 > 15.13 > Flashcards

15.13 Flashcards

1
Q

When might you want to motor the engine without ignition?

A

When doing maintenance checks

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2
Q

When might you only want to ingite the engine?

A

In flight after a flame out

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3
Q

What are gas turbine engines started by?

A

The HP compressor

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4
Q

Why would you want to accelerate the compressor?

A

To provide sufficient air to support combustion

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5
Q

Until when must the starter assist the engine?

A

Until it has reached above a self accelerating speed

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6
Q

How much torque should the motor create?

A

Excess to overcome compressor inertia and friction)

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7
Q

When is ignition turned on, then following after fuel suppled?

A

When the starter has accelerated compressor to the point where air is flowing though

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8
Q

When is the fuel flow rate not sufficient for the engine to accelerate?

A

At low (cranking) speeds

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9
Q

Are the starter and the ignitor switched off automatically or manually?

A

Automatically

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10
Q

What is a hot or hung false start?

A

When the starter doesn’t assist the acceleration so theres a delay in the starting cycle

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11
Q

What is the cartridge stater?

A

A small impulse type engine that is driven by high velocity gases

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12
Q

Where do the high velocity gases needed to drive the impulse type engine in the cartridge starter come from?

A

A burning cartridge

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13
Q

The power output from the turbine is passed through what two things before it rotates the engines?

A

A reduction gearbox (increases torque with lower rpm)

An automatic means of disconnection (when you don’t need the starter anymore)

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14
Q

What initiates the burning of the cartridge?

A

An electrically fired denoter. (cordite charge)

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15
Q

How does the cartridge system work?

A

Putting in a voltage (electricity) to start the ignition of the cartridge causes a release of hot gases. These hot gases go through a breech to a nozzle with allows flow to the turbine. This causes the turbine to rotate (under overboard exhaust collector)

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16
Q

What happens when the pressure rises above the preset maximum?

A

The air goes through a pressure relief valve which bypasses it through the hot air nozzle. (Want the two separate pressures to mix at the end to trim the pressure)

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17
Q

Advantages of air starter system?

A

Lighter, simple and more economical

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18
Q

What two things are consisted in an air starter system?

A

A reduction gearbox and a clutch which drives an output shaft connected to an engine

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19
Q

What air is used to start the starter turbine?

A

GPU air
APU
Crossfeed from running engine

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20
Q

What PSI is used at a time to start an air driven starter turbine?

A

30-50

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21
Q

When does the clutch automatically disengage?

A

When the engine accelerates to idling RPM and the starter motor ceases

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22
Q

What type of clutch is involved in a air starter?

A

A sprag clucth

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23
Q

When does the sprag clutch engage automatically?

A

When the rotor starts to turn

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24
Q

When does the sprag clutch disengage?o

A

As soon as the drive coupling turns more rapidly than rotor (It doesn’t need the starter motor anymore as it has reached self accelerating speed)

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25
Q

When does the ouput assemble and the drive coupling turn?

A

As long as the engine is on

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26
Q

What is set to open the turbine switch when the starter reaches cut out point?

A

A rotor switch actuator (Closes the valve and stops air supply to starter

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27
Q

What does a turbine rotor containment ring do?

A

Dissipate energy
Discharge energy coming off of the blades through the exhaust duct (in event of overspeed of turbine

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28
Q

What does the transmission housing also provide?

A

Lubrication

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29
Q

What is in the drain opening that allows you to see inside?

A

A sight glass

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30
Q

What does a magnetic drain plug do?

A

Picks up any ferrous metals that may be in the oil for the turbine (used to start the starter)

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31
Q

What 3 things are involved in maintenance?

A

Leaks
Oil level
Magnetic drain plug

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32
Q

What can be added through a port in the air starter?

A

Oil to the transmission housing sump

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33
Q

When is the sump vented?

A

During normal flight

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33
Q

The slope of the cam track is designed to provide what?

A

Small initial travel but high torque

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34
Q

If air starter valve fails to open (to allow air in to start) what must you do?

A

Manual over ride

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35
Q

What are the two types of electric starter systems?

A

Direct cranking
Starter generator

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36
Q

What type of electricity does the direct cranking electric starter use?

A

DC

37
Q

What does the clutch do when the engine reaches the a self sustaining speed on an electric starter system?

A

Automatically disengages

38
Q

The electrical supply is automatically cancelled when what?

A

When the starter motor is reduced after the engine has started efficiently or when the time cycle is completed

39
Q

Where are direct cranking systems used mostly?

A

On small turbine engines like APU’s or turboshaft engines

40
Q

How do direct cranking electrical systems work?

A

High or low voltages passed through a series of relays or resistance to allow voltage to build up as the starter gains speed.

41
Q

What does the direct cranking system also provide?

A

Power for ignition

42
Q

What is the difference between the starter generator and the direct cranking systems (The two electrical systems)

A

The starter generator can be used as a generator too (Don’t need an IDG) after the engines have reached self sustaining speed. (STARTER AND GENERATOR )

43
Q

In what type of starter motor is the shaft permanently engaged with the starter motor?

A

The starter generator

44
Q

What type of generator is a starter generator? What do they produce

A

Shunt generator (strong field and high torque)

45
Q

What is the C field used for in starter genrators?

A

Starting

46
Q

What is the shunt used for in a starter generator?

A

For voltage generation in the generator

47
Q

What does the undercurrent controller do?

A

controls the starter generator when it is used as a starter to provide positive action (To keep it running until the engine is running at a good speed)

48
Q

How many relays does the control block of the undercurrent relay

A
49
Q

What is the igniter used for?

A

To ignite the fuel then switches off

50
Q

What is different about the continuous ignition mode?

A

It uses a lower voltage and lower power

51
Q

When is continous ignition used?

A

If there is a possibility of engine flame out to relight the fuel and keep the engine from stopping

52
Q

What situation is continous ignition used in?

A

Take off, landing and some weather conditions (abnormal or emergancy)

53
Q

What is ignition cooled down with?

A

Fan airflow

54
Q

What type of ignition are most turbine engines equipped with?

A

Electronic type

55
Q

How many ignition sources do capacitor type systens consit of?

A

2 operating at operating from common DC source

56
Q

What are the DC sources used for ingition?

A

115VAC
The battery
Permenant magnetic generator

57
Q

What is the generator turned by?

A

The gearbox so produced power every time the engine is running

58
Q

Because of high altitudes, what can this cause the spark to do?

A

Become high intensity

59
Q

What is a safety factor ignition systems?

A

A dual system designed to fire two igniter plugs

60
Q

Before the electrical energy reaches the exciter unit, what does it pass through?

A

A filter that prevents noise voltage entering fuel electrical systems

61
Q

What drives the multi lobe

A

A multi-lobe/single lobe cam

62
Q

What are breaker points acctuated by?

A

Cams (multi/single)

63
Q

Once combustion is started what is the flame considered as?

A

Continuous

64
Q

What is the benefit of the ignitor being hermetically sealed?

A

Protects components from adverse operating conditions
Eliminate possibility of flashover (due to pressure change)
Sheilding against high frequency voltage

65
Q

What is the energy in the capacitor discharge exciter unit stored in?

A

Capacitor

66
Q

How many storage capacitors are there in discharge circuits?

A

2 (in the exciter unit)

67
Q

What happens to the resistance when the ignitor plug fires?

A

Drops to allow the larger capacitor to discharge across the gap

68
Q

What is the dual purpose of the spark?

A

Igniting abnormal fuel mixtures
Burning off deposits

69
Q

What is an exciter plug?

A

A dual unit that produces sparks for both igniter plugs

70
Q

A continuous series of sparks is produced until when?

A

The engine starts

71
Q

Why are exciters air cooled?

A

To prevent overheating during long use of continuous ignition

72
Q

When is an exception for the sparks being produced after the engine has started?

A

When continuous ignition

73
Q

Where are spark plugs used?

A

Reciprocating engine system

74
Q

What is the main difference between spark plugs and igniter plugs?

A

Igniter plugs’ electrode need to capable of withstanding a higher energy

75
Q

What causes electrode errosion?

A

High energy current

76
Q

How can you minimise electrode errosion?

A

Short periods of operation

77
Q

Why is the electrode gap larger in a igniter plug than a spark plug?

A

Operating pressures lower (in spark plug)
Spark can arc more easily (In igniter plug)

78
Q

What does a long reach ignitor mean?

A

It protrudes into the combustion chamber slightly for more effective results

79
Q

Where is a gap plug used?

A

Turbine engines

80
Q

What does a gap plug not do and what does this ensure?

A

Extend into the combustion chamber so it has a cooler operating temperature

81
Q

In a gap plug igniter plug, where does the spark arc?

A

Beyond the face of the combustion chamber liner

82
Q

How can the igniter be checked?

A

Hearing a clicking noise as the engine begins to start driven by the starter

Removing it and activating the start cycle and looking for a visible spark across it

83
Q

What does the ignition system wire insulation need to be?

A

Flexible with no evidence of arcing

84
Q

What must you do to the leads?

A

Clean them with a solvent and perform continuity checks

85
Q

When handling hot parts what PPE must you wear?

A

Hand PPE

86
Q

What is the most probable reason for accidental discharge of an ignitor plug?

A

Touching the ignitor

87
Q

What type of tools must be used?

A

Insulated

88
Q

Coupling nuts or connectors should not be what?

A

Touched with bare hands

89
Q

At what end must you disconnect igniter lead couplings first at?

A

The exciter end

Module 15 (18 decks)

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