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Engines > GTE Systems > Flashcards

GTE Systems Flashcards

1
Q

What are the functions of a fuel system

A

Combustion
Starting
Acceleration
Stable running under varying conditions

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2
Q

What are the requirements of a fuel system

A

Ease of flow
Quick and easy start
Complete combustion
High calorific value
Non-corrosive
No harmful by-product
Provide lubrication
Minimal fire hazard

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3
Q

What corrosive properties are present in a fuel

A

Water content
Sulphur compounds

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4
Q

Why are additives used in fuel

A

Reduce contamination and microbiological growth
Minimise corrosion
Enhance lubrication

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5
Q

Why is FSII used

A

Stops ice formation
Stops fungal growth

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6
Q

Why is AVTUR preferred to AVTAG

A

Reduced fire risk

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7
Q

What fuels are used as normal and emergency fuel types

A

Normal - AVTUR
Emergency - AVTAG

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8
Q

What are the 3 main sources of fire hazard

A

Fuel spillage ignited by spark
Fuel spillage ignited by hot surface
Flammable or explosive mixtures in fuel tanks

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9
Q

How is a fuel pump driven

A

By a gear train on the accessory gearbox

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10
Q

What 2 types of pump are used

A

Piston type
Spur gear

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11
Q

What is a spill valve used for

A

Controlling the angle of the swash plate in a piston pump

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12
Q

What device is used to control the fuel supply

A

Centrifugal governor

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13
Q

How does a centrifugal governor operate

A

Rest - weights held under spring pressure, fuel valve open.
Startup - drive increases, fuel valves start to close and fuel flow is restricted
Speed - as speed increases weights move further out under cent. Force until they are balanced by spring tension
Load change - if drive increases, speed will decrease and allow more fuel into into the engine. Reverse applies

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14
Q

Why does the fuel flow need to be restricted after startup

A

100% fuel flow is only needed for startup, not for 100% engine operation

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15
Q

What 2 types of filter are used in a free turbine fuel system

A

LP filter - for metered fuel
Fine filter - protects pump from debris

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16
Q

What is the purpose of FCU and throttle

A

Controls fuel flow from startup, acceleration to governor speed

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17
Q

What is the purpose of a PRV

A

Maintain system pressure

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18
Q

What is a torch igniter

A

Maintains flame until rotary atomisers can take over

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19
Q

What is an FCU 60psi and its purpose

A

Controls the flow of fuel to torch igniters until fuel pressure is above 60psi

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20
Q

What does FADEC stand for

A

Full authority digital engine control

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21
Q

What is the purpose of a free turbine governor

A

Maintains constant rotor rpm

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22
Q

What is the purpose of solenoid valves and NRV

A

Allows fuel to the torch igniters during start cycle, P2 air purges torch igniter of fuel when start is terminated

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23
Q

What are the advantages of using a FADEC system

A

Reduced weight and fuel consumption
Reduced pilot workload
Reduced stall and surge risk
Increased engine efficiency

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24
Q

What components does a FADEC system normally consist of

A

ECU, Hydro Mechanical unit and various sensors

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25
How is a FADEC system a redundant system
2 independent channels, switching from one input/output to the other to eliminate any failure
26
How often does a FADEC system determine wether to be active or on standby
30 milliseconds
27
What are some examples of fuel system maintenance activities
Throttle adjustment (rigging after disturbance) Filters replaced Rigid pipelines (security) Flexible pipelines (twists and damage) Leak checks Fuel flow tests (airframe system connection to engine)
28
Where are fuel flow tests carried out
NOT ON ENGINE On airframe system connection to the engine
29
What is the engine air system defined as
Airflow that does not directly contribute to engine thrust
30
What functions of an air system are performed internally
Sealing of bearings Purging torch igniters Anti-Icing Air pressure to FCU Internal cooling Pressure balancing
31
Why is P2 air used to purge the Torch igniter
To stop leftover fuel carbonising in the pipeline
32
What functions of an air system are done externally
Air conditioning Sand filtering Winch motor operation Cooling accessories
33
How do seals in oil systems use air to prevent leaks
Air is tapped from compressor and migrates through a labyrinth seal at higher pressure than oil, preventing oil loss
34
What is pressure balancing
HP air is fed onto the opposing face of compressor and turbine blades to overcome thrust loading
35
How is the combustion chamber cooled
Layer of air between engine casing and the combustion chamber
36
How are turbine blades cooled
Cool air fed through hollow blades to reduce their temperature
37
What is a hot air system used for
HP air from compressor used for ice removal and prevention
38
How are some of the engine mounted accessories cooled
Atmospheric air ducted in through louvres
39
What can occur when anti icing is switched on
Raise in JPT Drop in engine RPM
40
What are the 2 forms of ice protection system
Electrical Hot air
41
What is the purpose of a lubricant
Prevent surfaces touching and eliminate: Friction Wear Aids cooling
42
What are the 2 phases of lubrication
Boundary Film
43
What is boundary lubrication
Oil film between surfaces is only a few molecules thick
44
What is film lubrication
Rotating parts kept separate by a ring of oil
45
What oil is used in a GTE
OX— , a synthetic oil
46
What are the shafts in a GTE supported by
Ball or roller bearings
47
What substances are used to remove heat from an engine
Air Oil
48
What 3 bearings are used in oil systems
Roller Bearings - radial and axial Ball bearings - axial or thrust loads Squeeze film - minimise vibration
49
What is a dry vs a wet sump
Dry - oil is kept in a separate tank Wet - oil is contained in the sump
50
What sump do most GTE use
Dry sump
51
How does a squeeze film work
Small clearance between bearing and housing, filled with oil to reduce vibration and fatigue risk
52
What types of seal are used in oil systems
Carbon Brush Lip Labyrinth
53
How does a labyrinth seal work
Pressurised air is directed towards bearings, which stops the lower pressure oil from escaping from the bearing surface
54
Which seals rely on physical contact with the assemble to prevent leaks
Brush Lip Carbon
55
What are the 2 methods of lubrication
Oil mist - compressed air atomises the oil, aids cooling Oil jet - sprays oil directly onto bearing
56
What is the advantage of an oil jet
Controllable Reliable Regulate quantity and pressure
57
What is the purpose of an oil system
Supply an adequate amount of oil and deliver it to various parts of an engine
58
What are the 2 types of oil systems
Recirculatory Expendable
59
What are the 2 types of recirculatory system
Pressure relief valve system Full flow system
60
What is the purpose of a PRV recirculatory system
Maintains system pressure over higher engine speeds, using a PRV to maintain it
61
What are the advantages of a Full flow system
Pump delivers oil to bearings directly Allows smaller pumps to supply sufficient oil
62
What is the typical PRV oil system path
Tank Pressure Pump PRV Filter Check Valve Fine filter Engine Mag plug Filter Pump FCOC, ACOC
63
What can be used to remove air from oil
Baffles Centrifugal breather
64
Where are scavenge pumps used
Any areas that need oil delivered to them
65
How does a centrifugal breather work
Rotating components separate heavier oil from air. Oil is returned to tank and air is vented
66
What can be fitted to oil systems while maintenance is being carried out to stop leakages
Blanks / caps
67
What maintenance is carried out on oil systems
Consumption monitoring Maintaining oil level Probe monitoring Filter replacements Leak checks Pipe inspections
68
What health and safety precautions should be taken when working with oil systems
Barrier cream Wash hands before eating Use of soap and water Watch for open cuts and grazes Relevant PPE to be used
69
What are the advantages of a Full flow system
Provides suitable oil flow Suitable pressure At all engine speeds
70
What does APU stand for
Auxiliary power unit
71
What is the APU used for
Powering all ancillary services required while the aircraft is on the ground
72
Where is the APU normally fitted
In passenger aircraft, in a fireproof enclosure in the tail cone
73
How many stage compressors and turbines does an APU have
Single stage compressor Single combustion chamber Single stage turbine
74
When would the APU need to be shut down
Low power Over-Speed Overheating Loss of oil pressure Fire
75
What are the 4 basic components of a starting system
Starter motor Ignition circuit Fuel/Air supply Control system
76
What is the purpose of the starter motor
Will take the engine up to self sustaining speed, turns without ignition or fuel
77
What does an ignition circuit do
High energy ignition system to start combustion
78
What does a control system in a starting system do
Monitors the start sequence and protects speed and temperature limits
79
What is the definition of self sustaining speed
Lowest rpm from which the turbine will drive the engine without help from a starter motor
80
What are the 4 types of starter
Electric Gas Air Hydraulic
81
What services can an APU provide
Pneumatics Hydraulics Electrics
82
What are the advantages of a starter generator
Less weight Low cost No disengagement mechanism
83
How can overheating be prevented on a starter motor
Restricted to an operating time of 20 seconds for 3 attempts before having to be left for 15 minutes for another attempt
84
What are the 3 types of igniter plug
Surface discharge plug Air gap plug Torch igniter
85
What does HEIU stand for
High Energy Ignition unit
86
What is the purpose of HEIUs
Deliver high voltage, high current discharge at an igniter plug
87
What must be done with the HEIU when the electrical supply is disconnected
Disconnect LT lead Allow 1 minute for the capacitor to discharge
88
When else apart from start up can the ignition system be used
Testing Re-Light Anti Icing Turbulence Takeoff in heavy rain
89
What maintenance can be checked on starter systems
Security of attachment Injector blockage Igniters test Ignition lead damage
90
What services does an APU provide
Electronics Hydraulics Pneumatics Air conditioning
91
What systems are monitored on a GTE
Engine Temperature Oil pressure and temperature Engine rpm Torque Fuel flow Vibration Engine pressure ratio (EPR)
92
What is used to measure JPT
Thermocouples Pyrometers
93
How does a thermocouple work
Hot air is allowed to pass between 2 dissimilar metals, creating an electrical signal which is transmitted to the cockpit
94
What is EPR
Ratio between turbine discharge pressure and compressor inlet pressure
95
How does a pyrometer work
Infra red detectors that measure the temperature of the turbine, requires a supply of bleed air to clean the lens
96
How is vibration monitored
Materials that produce an electric signal when squeezed by forces during vibration, transmit the signal to the cockpit
97
How is fuel flow measured
Fuel passed through a tube Impeller imposes a spin onto fuel Spinning fuel turns a turbine which records and sends signal based on how far it turns
98
What is used to separate engine compartments from fire spreading
Titanium / Stainless steel bulkheads
99
How are fires sensed in the engine
FireWire
100
How does FireWire work
When FireWire heats up, the resistance of the filling material drops, causing the electricity to pass to the outer casing. This sends a signal to the cockpit
101
How can fire be indicated in the cockpit?
Alarm Lights Audible warnings
102
What can destroy the effectiveness of the FireWire
Moisture destroys the negative temperature coefficient
103
What is the traditional extinguishant for engine fires
BCF, charged with nitrogen
104
How is the FireWire response tested
Simulates an overheat condition, does not operate the system
105
How is extinguishant directed onto the fire
Discharged from containers through a series of spray nozzles
106
What is a 2 shot system
A system that allows 2 bottles to be used on either engine, or both
107
How long should a pilot wait after extinguishing 1 bottle to use another
15 seconds
108
109
What maintenance can be carried out on fire systems
Checking extinguishant pressure Weighing fire bottles
110
What are the 3 typical engine controls found in a GTE
HP cock Throttle Centrifugal governor
111
What are the 3 types of control cables
Bowden cables Teleflex Bowden flex
112
What are Bowden cables usually used for
Lightly loaded components In tension only Relies on a spring for return
113
What is a teleflex system usually used for
Pushing and pulling Tension and compression
114
What are bowdenflex cables used for
Withstand compression and tension Can withstand high temperatures
115
What maintenance needs to be checked and carried out on GTE engine controls
Control run checks Rigging Wear on control stops Freedom of movement Leaks

Engines (5 decks)

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