Air Systems & Starting and Ignition

Question 1

A turbine engine ignition system contains three major components:

Answer 1

a high voltage exciter,

high voltage transmission lead,

and an igniter plug.

Question 2

The ________ is powered by the aircraft electrical system, either D.C. or A.C., or a dedicated permanent magnet alternator (PMA) and produces a high voltage pulse through the igniter lead to the plug.

Answer 2

exciter

Question 3

The _________ then arcs (spark
jumps a gap) to ignite the fuel/air mixture in the combustion
chamber

Answer 3

igniter plug

Question 4

Modern gas turbine engine ignition systems are of the high
intensity capacitor discharge type with either __________ or ________

Answer 4

Intermittent Duty or Extended Duty cycles.

Question 5

____________ - sufficiently high current may cause overheat damage to their units, so they have a restricted duty cycle based on operating time, followed by a cooling off period

Answer 5

Intermittent Duty types

Question 6

___________ - have long duty cycles, or in some cases are rated for continuous duty, meaning they have no
time limits all.

Answer 6

Extended Duty types

Question 7

After a normal start, __________ is no longer needed and the ___________ is deactivated

Answer 7

ignition, ignition system

Question 8

_______________ is used for starting all jet engines and a dual system is always fitted.

Answer 8

High-energy (H.E.) ignition

Question 9

Each system has an ignition unit connected to its own ________________, the two plugs being situated in different positions in the combustion system.

Answer 9

igniter plug

Question 10

Ignition units are rated in ________.

Answer 10

Joules

Question 11

They are designed to give
outputs which may vary according to requirements.

Answer 11

Ignition

Question 12

A _______________ (e.g. twelve joule) is necessary to ensure that
the engine will obtain a satisfactory relight at high altitudes
and is sometimes necessary for starting

Answer 12

high value output

Question 13

a ___________ (e.g. three to six joule) is preferred because it results in a longer life of the igniter
plug and ignition unit.

Answer 13

low value output

Question 14

under certain flight conditions, such as icing or take-off in heavy rain or snow, it may be necessary to have
the ignition system continuously operating to give an
automatic relight should flame extinction occur. it is preferred to use ___________

Answer 14

low value output

Question 15

There are two basic types of igniter plug; the _________ or _____________ and the ______________.

Answer 15

constricted/constrained air gap type, shunted surface discharge type

Question 16

The air gap type is similar in operation to
the ________________

Answer 16

conventional reciprocating engine spark plug

Question 17

The air gap type is similar in operation to
the conventional reciprocating engine spark plug, but has a ________________

Answer 17

larger air gap between the electrode and body for the
spark to cross

Question 18

A potential difference of approximately ___________ is required to ionize the gap before a spark will occur. This
high voltage requires very good insulation throughout the
circuit

Answer 18

25,000 volts

Question 19

The _____________ has the end of the
insulator formed by a semi
conducting pellet which permits
an electrical leakage from the
central high tension electrode to
the body

Answer 19

surface discharge igniter
plug

Question 20

The discharge takes the form of a high intensity flashover from the electrode to the body and only requires a potential difference of approximately ____________ for operation.

Answer 20

2000 volts

Question 21

igniter types

Answer 21

constrained air gap type
shunted surface discharge type

Question 22

types of ignition by duration

Answer 22

intermittent duty
extended duty

Question 23

types of ignition by output

Answer 23

low value output
high value output

Question 24

Two separate systems are required to ensure that a gas
turbine engine will start satisfactorily:

Answer 24

Firstly, provision must be made for the compressor and turbine
- Engine Idling RPM

Secondly, provision must be made for ignition

Question 25

The starter motor must _____________ and transmit it to the engine rotating assembly

Answer 25

produce a high torque

Question 26

Methods of Starting

Answer 26

Electric Starter Cartridge Starter Isopropyl-Nitrate Starter Air Starter Gas Turbine Starter Hydraulic Starter

Question 27

The _____________ is usually a direct current (D.C.) electric motor

Answer 27

electric starter

Question 28

automatically disengages after the engine has reached a self-sustaining speed

Answer 28

Clutch (Electric Starter)

Question 29

It also provides the power for the operation of the ignition system.

Answer 29

Electric Starter

Question 30

The __________ is automatically cancelled when the starter load is reduced after the engine has satisfactorily started or when the time cycle is completed.

Answer 30

electrical supply

Question 31

___________ is sometimes used on military engines and provides a quick independent method of starting.

Answer 31

Cartridge starting

Question 32

The _____________ is basically a small impulse-type turbine that is driven by high velocity gases from a burning cartridge.

Answer 32

starter motor

Question 33

An ___________ initiates the burning of the cartridge charge.

Answer 33

electrically fired detonator

Question 34

CARTRIDGE The power output of the turbine is passed through a __________ and an ___________ to rotate the engine

Answer 34

reduction gear, automatic disconnect mechanism

Question 35

This type of starter provides a high power output and gives rapid starting characteristics.

Answer 35

Isopropyl-nitrate starter

Question 36

In this instance, the turbine is rotated by high pressure gases resulting from the combustion of ___________.

Answer 36

isopropyl-nitrate

Question 37

This fuel is sprayed into a combustion chamber, which forms part of the starter, where it is electrically ignited by a high energy ignition system.

Answer 37

Iso-propyl-nitrate

Question 38

A ________ supplies the fuel to the combustion chamber from a storage tank and an ____________ scavenges the starter combustion chamber of fumes before each start.

Answer 38

pump, air pump

Question 39

______________ is used on most commercial and some military jet engines.

Answer 39

Air starting

Question 40

advantage of air over other starting system

Answer 40

light, simple and economical to operate.

Question 41

An _____________ transmits power through a reduction gear and clutch to the starter output shaft which is connected to the engine

Answer 41

air starter motor

Question 42

The ____________ is rotated by air taken from an external ground supply, an auxiliary power unit (A.P.U.) or as a cross feed from a running engine.

Answer 42

starter turbine

Question 43

The air supply to the starter is controlled by an ___________ and ____________

Answer 43

electrically operated control and pressure reducing valve.

Question 44

The clutch also automatically disengages as the engine accelerates up to __________ and the rotation of the starter ceases

Answer 44

idling r.p.m.

Question 45

A _______________ is used for some jet engines and is completely self-contained.

Answer 45

gas turbine starter

Question 46

It has its own fuel and ignition system, starting system (usually electric or hydraulic) and self-contained oil system.

Answer 46

Gas Turbine Engine

Question 47

This type of starter is economical to operate and provides a high power output for a comparatively low weight.

Answer 47

Gas Turbine Engine

Question 48

The starter consists of a small, compact gas turbine engine, usually featuring a ____________ , a _____________ and a ____________________.

Answer 48

turbine-driven centrifugal compressor, reverse flow combustion system, mechanically independent free-power turbine

Question 49

The free power turbine is connected to the main engine via a ___________

Answer 49

two stage epicyclic reduction gear, automatic clutch and output shaft

Question 50

_____________ is used for starting some small jet engines.

Answer 50

Hydraulic starting

Question 51

Methods of transmitting the torque to the engine may vary, but a typical system would include a ___________

Answer 51

reduction gear and clutch assembly

Question 52

Power to rotate the pump/starter is provided by hydraulic pressure from a ground supply unit

Answer 52

hydraulic

Question 53

powered by dc motor

Answer 53

electric

Question 54

powered by burning cartridge

Answer 54

cartridge

Question 55

powered by cobmbustion

Answer 55

Isopropyl nitrate

Question 56

powered by air coming from external source

Answer 56

Air

Question 57

compact/ mini gte starter

Answer 57

Gas turbiine engine

Question 58

powered by hydraulic pressure from GPU`

Answer 58

Hydraulic

Question 59

defines as those airflows which do not directly contribute to the engine thrust

Answer 59

Internal air system

Question 60

the system also supplies air for the aircraft services. up to ___ of the total engine core mass airflow may be used for these various functions

Answer 60

1/5

Question 61

important consideration at the design stage of a gte is the need to

Answer 61

parts do not absorbs heat

Question 62

areas which requires air cooling

Answer 62

combustor and turbine

Question 63

used to control the temperature of the compressor shafts and discs by either cooling or heating them.

Answer 63

cooling air

Question 64

ensures even temperature distribution and maintain minimum blade tip and seal clearances

Answer 64

Cooling air

Question 65

dependent upon hight turbine entry temperature, which is limited by the turbine blade and nozzle guide vane materials

Answer 65

High thermal efficiency

Question 66

Continuous cooling of these components allows their environmental operating temperature to ______________

Answer 66

exceed the material's melting point without affecting blade and vane integrity

Question 67

require the discs to be cooled and thus prevent thermal fatigue and uncontrolled expansion and contraction rates

Answer 67

Heat conduction from turbine blades to turbine disc

Question 68

most commonn ways of cooling the components

Answer 68

engine bleed air

Question 69

Two types of blade cooling

Answer 69

Convection Transpiration

Question 70

holes in the tip

Answer 70

convection

Question 71

porous material

Answer 71

transpiration

Question 72

grat practical benefit but development has lead to multi pass internal cooling of blades, impingement cooling of vanes with external air film cooling of both vanes and blades

Answer 72

single pass internal cooling

Question 73

example of accessory cooling

Answer 73

generator

Question 74

when ___________ is used for cooling, the source may be the compressor or atmospheric air ducted from the intake louvres in the engine cowlings

Answer 74

air

Question 75

various sealing methods are used on _________

Answer 75

gte

Question 76

use of seals

Answer 76

prevent oil leakage control cooling airflows prevent ingress of the mainstream gas into the turbine disc cavities

Question 77

types of seal

Answer 77

labyrinth ring carbon hydraulic brush

Question 78

air systems cooling

Answer 78

turbine cooling acessory cooling

Question 79

Two separate systems are required to ensure that a gas turbine engine will start satisfactorily

Answer 79

compressor and turbine ignition

Question 80

The starter motor must produce a ____________ and transmit it to the engine rotating assembly in a manner that provides smooth acceleration from rest up to a speed at which the gas flow through the engine provides _____________

Answer 80

high torque; sufficient power for the engine turbine to take over.

Question 81

Methods of Starting

Answer 81

Electric Starter Cartridge Starter Isopropyl Nitrate Starter Air Starter Gas Turbine Starter Hydraulic Starter

Question 82

usually a direct current (D.C.) electric motor coupled to the engine through a reduction gear and ratchet mechanism, or clutch, which automatically disengages after the engine has reached a self-sustaining speed.

Answer 82

The electric starter

Question 83

provides the power for the operation of the ignition system. The electrical supply is automatically cancelled when the starter load is reduced after the engine has satisfactorily started or when the time cycle is completed

Answer 83

Electric Starter

Question 84

is sometimes used on military engines and provides a quick independent method of starting.

Answer 84

Cartridge starter

Question 85

The starter motor is basically a small impulse-type turbine that is driven by high velocity gases from a burning cartridge.

Answer 85

Cartridge

Question 86

An electrically fired detonator initiates the burning of the __________charge.

Answer 86

cartridge

Question 87

This type of starter provides a high power output and gives rapid starting characteristics. I

Answer 87

Isopropyl-nitrate

Question 88

This fuel is sprayed into a combustion chamber, which forms part of the starter, where it is electrically ignited by a high energy ignition system

Answer 88

Iso-propyl nitrate

Question 89

is used on most commercial and some military jet engines.

Answer 89

Air starting

Question 90

It has many advantages over other starting systems, and is comparatively light, simple and economical to operate. A

Answer 90

Air starting

Question 91

A _________ is used for some jet engines and is completely self-contained. I

Answer 91

gas turbine engine starter

Question 92

The starter consists of a small, compact gas turbine engine

Answer 92

GasTurbineEngine

Question 93

is used for starting some small jet engines

Answer 93

Hydraulic starting

Question 94

Power to rotate the pump/starter is provided by hydraulic pressure from a ground supply unit

Answer 94

Hydraulic