AGK Engines Flashcards
1
Q
Ignition Timing…
A
Is performed by the magnetos .
Is necessary as it takes a finite time for the mixture to burn.
2
Q
Which engine initiates combustion by the heat of compression
A
Deisel engine
3
Q
Which engine uses a spark to initiate ignition
A
Petrol engine
4
Q
Name the strokes in a 4 stroke engine
A
Induction, Compression, Power, Exhaust
5
Q
Flame rate of aviation fuel mixed with air
A
60/80 ft per second
(18-24m)
6
Q
The crank assembly is comprised of…
A
Crankshaft
Connecting rods
Pistons
7
Q
Hydraulic tappets are used to…
A
automatically adjust the tappet clearance
8
Q
Why are valves often filled with sodium ?
A
To take heat away
9
Q
Name 4 EMF variables
A
Magnet size
Conductor length
Perpendicular angle
Rate of charge
10
Q
How long should the starter operating light take to switch off ?
A
30 Seconds
11
Q
An impulse coupling..
A
Gives you a higher energy retarded spark.
12
Q
A high tension booster is…
A
A vibrator directly connected to the high tension side. (shower of sparks)
13
Q
A low tension booster is…
A
A set of pulses to the primary circuit (low tension side)
14
Q
Pre flight magneto checks are…
A
Drop check
Dead cut check
15
Q
RPM drop range on a drop magneto check
A
Drop of 100-175 indicates normal magneto operation.
Drop greater than 400 means there may be a faulty spark plug and should be reported immediately.
16
Q
A blocked spark plug gap is said to be …
A
Fouled
17
Q
A spark plugs body forms an…
A
Electrode
18
Q
AVGAS is made up of ?
A
15% carbon 85% hydrogen
19
Q
Octane rating is…
A
A measure of resistance to detonation
20
Q
Detonation flame rate ?
A
1000 ft/s
21
Q
what colour is AVGAS 100LL
A
Blue
and environmentally better
22
Q
What colour is AVGAS 100
A
Green
and environmentally worse
23
Q
A fuel sample must be…
A
Clear and bright
Free of sediment
No entrained water
have a max water content of 30ppm
24
Q
Detonation causes
A
Fuel with too low octane (poor anti knock)
Incorrect (weak) mixture
Anything that could unduly raise temperature or pressure.
High engine temperature
25
Pre ignition causes
Hot debris within the cylinder
(typically carbon deposits)
Ignition malfunction (damaged spark plug)
High cylinder temperatures
26
Mixture ratios
20:1 Lean (increased detonation risk)
15:1 Chemically correct (ideal ratio)(EGT Peak)
8:1 Rich (increased detonation risk)
27
Takeoff and cruise mixes should be..
Takeoff 11:1
Cruise 17:1
28
Ineffective crank angle is ?
The period of relatively little movement of the piston around the TDC and BDC
29
Inlet valve lag is when...
The inlet valve remains open just after BDC as the compression stroke begins to help fill the chamber. The valve closes just after the piton leaves the ineffective crank angle.
30
Inlet valve lead is when...
Inlet valve opened early, just before TDC, exhaust valve is still open at the end of the exhaust stroke
31
Exhaust valve lead is when...
Both valves are closed at the start of the power stroke, most of the work is done before the piston reaches BDC, so the exhaust valve opens before the end of the power stroke. Provides a longer period to clear the cylinder of waste gasses.
32
Exhaust valve lag is when...
The exhaust valve remains open until slightly after the TDC, remaining gas exits under its own momentum.
33
TDC
Top Dead Center
34
BDC
Bottom Dead Center
35
Where does valve overlap occur ?
Around TDC between the exhaust and induction strokes.
36
Prime carburettor icing temperature and key condition ?
+18 to +25 C
and high humidity levels
Low power levels
37
Carb icing prevention ?
Carburettor heating
38
Carb icing symptoms ?
Loss of rpm
Reduced inlet MAP
Decreased EGT
Rough running
Jammed throttle
Engine stops
39
Carburettor alternative ?
Fuel injection, fuel is injected to the cylinders directly so no need for a carburettor.
40
Diesel engine is primed how ?
By using the accelerator pump
41
Fuel must ...
Have a lot of energy
Be able to form a vapour
Be able to burn quickly
42
AVGAS has a SG of ...
0.72 at 15 C
43
what can occur if fuel vaporises in the fuel lines or pumps. This causes partial or complete loss of engine power.
Vapour lock
44
What is the extremely rapid chemical decomposition of the mixture after burning has begun. May be heard as knocking sound.
Detonation
45
What is the ignition of the mixture before the spark plug has sparked. Caused by hot spots in the cylinder.
Pre-ignition
46
Symptoms for pre-ignition and detonation ?
Rough running
Power loss
Overheating
47
What is added to fuel to reduce detonation ?
Lead
AVGAS 100LL (Low lead)
48
What is the stoichiometric fuel mix ?
15:1, but cannot be used as engine would overheat
49
Which engine has a lower power to weight ratio, Why ?
Diesel
They are heavier but have the same output as a lighter petrol engine and lower max RPM. But it has a greater compression ratio
50
What is a carburettors purpose ?
To mix fuel and air to the correct ratio. Fuel is supplied by an engine driven pump. Air is supplied via the air intake.
51
How is mixture manually controlled ?
A mixture control lever in the cockpit
52
At low power setting the butterfly valve is... ?
Almost closed
53
Pre-ignition is ?
The ignition of mixture before the spark plug has fired
54
RPM gauge measures ?
Crankshaft RPM
55
Manifold pressure gauge ?
Measures manifold pressures in InHg
56
Boost pressure gauge ?
Measures manifold pressure in PSI relative to sea level pressure
57
Oil pressure gauge ?
Measures oil pressure just after the oil filter
58
Oil temperature gauge ?
Measures oil temperature in oil return line
59
CHT gauge ?
Measures the temperature of the hottest cylinder
60
EGT gauge ?
Measures the temperature of the exhaust gas stream
61
Fuel pressure gauge ?
Measures the fuel pump output pressure
62
Induction temperature gauge ?
Measures the carburettor inlet temperature
63
Camber line and chord line are between ?
Leading and trailing edge
Chord is the length of the chord line
64
Does a petrol or diesel engine have greater thermal efficiency ?
Diesel.
It has a higher compression ratio; 20:1 whereas petrol engines only have a 10:1 ratio.
65
What device is fitted to measure cylinder head temperature effectively ?
A Thermocouple
66
Engine PWR output ?
Torque x RPM
67
how is magneto switched off ?
Grounding the magneto
68
What happens to AoA of a fixed pitch prop as A/C accelerates along a runway ?
Decreases
69
Rich mixture in climbing segments results in ?
A gradually rich mixture as you climb (less dense air)
70
Why does a cylinder have 2 spark plugs ?
It reduces time for complete combustion
71
How is impeller driven ?
Diversion of exhaust gasses by waste gate, using energy that would otherwise be wasted
72
What is the angle between the blade chord and the plane of rotation ?
Blade pitch
73
Flat rating is used in what ambient conditions ?
Cold
74
What does jet thrust vary with
Altitude
Air density
Air speed
Engine RPM
75
Hot and high conditions are associated with… ?
The least thrust available from the engine
76
Propulsive power is … ?
Thrust x Aircraft velocity
77
RAM effect is associated with ?
High airspeed
78
Combustion occurs at a constant … ?
Pressure
79
What does a compressor do to gas flow ?
Gives it energy
80
Flat rating is used in what conditions ?
Cold
81
Constant speed propeller… ?
Adjusts pitch to ensure propeller runs at optimum RPM for airspeed
82
How is blade pitch altered ?
PCU in the propeller hub
83
Coarse pitch …?
Absorbs most power, creates most rotational drag
84
Fine pitch… ?
Absorbs the least power
Creates a lot of rotational drag if not running (Engine failure)
85
What prevents blades from going fully coarse on engine shut down ?
Centrifugal latch
86
Feathered blades are ?
Fully coarse to provide the minimum drag
87
Un-feathering is ?
Putting the blades to a finer pitch to allow engine restart in flight
88
What is fitted to multi engine aircraft to prevent problems caused by asymmetric drag ?
Auto-feather system
89
How is reverse thrust achieved ?
By setting the pitch to behind fully fine
(Beta range)
90
How is reverse thrust prevented ?
Weight on wheels operated fine pitch stop
91
How is cabin noise reduced ?
Synchronising or synchrophasing to avoid build up of pressure waves
92
How to avoid over boosting ?
Rev up: Power back
93
When must CSU operation be checked ?
Before flight, done by operating RPM lever
94
Which system always has a governor fitted ?
Constant speed, variable pitch
95
What sound frequency is produced from a propeller engine commonly
90 Db
96
Fining blade pitch … ?
Increases RPM
97
What pitch is wanted for landing and takeoff ?
Fine pitch
98
Ideal cruise pitch ?
Coarse
99
How is the propeller driven ?
Engine torque (RPM)
100
Impact on AoA on a variable pitch prop with increase or decrease of TAS and RPM ?
It remains the same
101
Effect of TAS on AoA on a fixed pitch prop ?
AoA is inversely proportional to TAS
(TAS increases AoA decreases)
102
What does LP spool comprise
LP compressor or fan
LP turbine
Shaft
103
What does HP spoil comprise
HP compressor
HP turbine
104
For optimal efficiency… ?
Fan must run at relatively low RPM
Core must run at a very high rpm
Multiple spools allow this to happen
105
Bypass ratio is ?
The ratio of bypass air mass flow to core mass flow.
( air entering the core Vs air going in bypass duct.
If 10 tonnes of air enter inlet, and 1 comes out the exhaust, bypass ratio is 9:1)
106
What do some turbine engines have to drive the propeller ?
Free turbine
107
Pure turbojet has no ?
Bypass duct
Exhaust jet velocity is very high instead
108
An engine which uses a gas turbine to drive a helicopter rotor is a ?
Turbo shaft
109
Advantage of multi spool designs is ?
Each spool runs at its optimum speed
110
Most moderns commercial jet aircraft use ?
Turbofan engines
111
Read part of pitot-style inlet forms a …?
Divergent duct
112
Pitot style inlet cannot guarantee stable inlet conditions:
When contaminated with ice
At very high angle of attack
In severe turbulence
I’m very high crosswinds
113
Air inlet fan has sensors to detect
Inlet temperature
Inept pressure
(Amongst other things)
114
Nacelle functions ?
Reduce compressor noise
Provide structure for bypass duct
Streamline engine installation
Protect external engine components
115
Two types of compressor ?
Centrifugal
Axial flow
116
Compression ratio on a centrifugal compressor ?
4.5:1 per stage
A maximum of 2 stages in series can be employed
117
What is a “stage” in an axial flow compressor ?
A set of rotating rotors and stationary stators, axial flow compressor comprises many stages
118
Axial flow compression ratio ?
1.1-1.2:1 (10-20%) per stage
119
What happens to Velocity pressure and temperature going through a rotor ?
Velocity - Increases
Pressure (static) - decreases
Temperature - Increases
120
What happens to velocity, pressure and temperature in a stator ?
Velocity - decreases
Pressure (static) - increases
Temperature - increases
121
Variable Inlet guide veins … ?
Swivel to deliver air at correct AoA to first stage of compressor
122
Why is clearance between rotor sections and compressor case very small ?
To prevent tip losses
123
Diffuser role ?
Converts kinetic energy into static pressure
124
Stall or surge indicators
Low RPM
Banging noises
High temp
125
Axial compressors are vulnerable to … ?
Foreign object damage
126
Positives of centrifugal compressor
Less prone to surges
Less susceptible to FOD
Shorter, so more compact engines
Reasonably Efficient
127
Negatives of a Centrifugal compressor
Low compression ratio
Less efficient than an axial flow compressor
Requires larger frontal area
128
Axial Flow compressor P+N
Very efficient
High compression ratio
Vulnerable to FOD
Can suffer aerodynamic instability
129
Stall and surge cheats
Multiple stools
Bleed valves
Variable inlet guide veins (VIGV) or variable station valves (VSVs)
130
Stall and surge avoidance
Before flight check for ice and damage
Avoid starting in cross or tailwind
Avoid extreme angles of attack
131
The entire axial flow compressor is located in … ?
A convergent duct to help sustain airflow against rising static pressure
132
Flow reversal through an axial flow compressor is called ?
Compressor surge
133
Diffuser at the back of an axial flow compressor uses a …. Duct ?
Divergent
134
External air bleed- alternate name + uses
Customer bleed
To supply hot air or high pressure to aircraft systems, such as air con or anti icing
Can be switched off manually.
135
Internal Air bleed functions
Spinner anti icing
Pressurised internal cavities
Pressurised bearing housings
136
How to stop an internal engine over heat ?
Turn off engines
137
Role of combustion chamber ?
To mid air and fuel to allow efficient burning
138
Pressure across Gas turbine engine ?
GTE is a constant pressure engine, combustion does not create an increase
139
How does the distribution of air go into the combustion chamber ?
20% goes through a ‘snout’ in ceramic lining, 80% goes around
140
Air fuel ratio in GTE
45-130:1
In the flame is 15:1
141
What does a primary airflow feed ?
Combustion flame, via a swirled valve and recirculating vortex.
Reducing airflow speed to 3 m/s
142
Where is gas ignited ?
Primary zone
143
What does a combustor drain do ?
Allows pooled fuel to drain away preventing a hot start or torching
144
Cannular combustion chambers
Multiple chambers, Lots of little flames, lots of cooling tubes.
145
Turbo annular combustion chamber
Radially placed, multiple flame tubes with different nozzles.
146
Annular combustor (modern)
Fuel nozzles arranged radially injecting into one large flame tube
147
Air spray injectors
Takes in air to creates a swirl and mixes it with fuel to make a toroidal flame in the primary zone, controlled by FADEC
148
Advantage of air spray injectors ?
Low carbon emissions
Lower pollutants
149
What is the most sensitive part of the GTE
The turbine assembly is most temperature and pressure sensitive part and is life critical
150
What happens to turbine size heading away from heat
It increases
151
What does the turbine drive ?
Compressor, front fan, accessory gearbox
152
Compressor stage is ?
Rotating rotor
Stationary stator
153
Turbine stage is made up of
Stationary nozzle guide vein (NGV)
Rotating turbine rotor
154
What does the turbine do ?
Extract kinetic energy to creat rotation of turbine discs and thus the spool shaft
155
Impact on T, sP, V across the turbine
Decreases
156
How is the turbine system housed ?
In a divergent duct
157
Impulse turbines
Driven by a fluid jet against the blade, rotation is only achieved through this action, causing an impulse force which drives the turbine.
158
Impulse turbine nozzle and rotor setup
Nozzle - convergent (creates a jet flow which strikes the blades)
Rotor - constant area
159
Reaction turbine
Is designed in the opposite to impulse and utilises newton’s 3rd law. Air accelerated through convergent ducts creating a reaction force
160
Reaction turbine rotor and stator set up
Nozzle - constant area
Rotor - convergent shape (accelerates air through it)
161
P/V/T across an impulse turbine (NGV/Rotor)
NGV
P- Decreases
V - Increases
T - Decreases
Rotor
P - Decreases
V - Increases
T - Decreases
162
P/V/T across an Impulse/reaction turbine (NGV/Rotor)
NGV
P - Decrease
V - Increase
T - Decrease
Rotor
P - Decrease
V - Increase
T - Decrease
163
P/V/T across a reaction turbine (NGV/Rotor)
NGV
P - No change
V - No change
T - No change
Rotor
P - Decrease
V - Increase
T - Decrease
164
How are blades connected to discs
Fir tree connection, increases surface area whilst creating multiple load paths
165
How is blade stress monitored ?
HCF - high number of small stresses (vibrations)
LCF - low number of large stresses
166
How is blade stress reduced ?
Reducing blade temp
Single Crystal tech sees alloys moulded in a specific manor to reduce it
167
Active clearance control (ACC) role ?
Ensures minimum loss within turbine, using hot bleed air to expand the turbine case to maintain small tip clearances.
168
How is blade tip losses reduced ?
Shrouding
169
Typical exhaust system composition
Jet pipe
Propelling nozzle
An exhaust cone
170
Purpose of exhaust system ?
To maximise thrust by accelerating air rear wards
171
When does the propelling nozzle become choked ?
When nozzle velocity reaches M1.0
172
P/V/T effect in exhaust
P + T fall
V may increase
173
How is exhaust noise reduced ?
Shrouding high velocity core exhaust gas with cold bypass air. Mixer units can be used instead
174
What does scarfing do ?
Reduces noise on modern A/C
175
How is reverse thrust produced ?
By reversing some of the hot stream with blocker doors or clamshells or buckets
176
How is reverse thrust produced on high bypass engines ?
Reverse thrust is produced by reversing some of the bypass air through cascade vanes and doors in the nacelle
177
How is inflight reverse thrust prevented ?
Interlocks.
Airbus won’t let reverse thrust be used at low speeds.
178
Cold stream reversal is used on ?
Larger, high bypass engines
179
Minimum number of reverse thrust protections ?
3
One on flight deck
(Visual indication of doors, green for in operation, Amber for unlocked)
Two operated by engine
180
How are blocker doors operated ?
Hydraulically
181
How are clamshells and buckets operated
Pneumatically
182
How is engine temp measured?
Thermocouple
183
Thermocouple composition?
Two dis-similar metals joined to form a junction with a loop, a small voltage is produced when exposed to heat
184
EGT ?
Exhaust gas temperature
185
TGT
Turbine gas temperature
186
TET
Turbine engine temperature
187
JPT
Jet pipe temperature
188
How are rotating shafts supported
Needle roller bearings
189
How are thrust loads generated by shafts transferred to the main engine casing ?
Ball bearings, so shafts must have both types of bearing
190
How are bearings lubricated and cooled ?
By engine oil
191
Why does the filter have a bypass ?
Incase it becomes blocked
192
What surrounds each set of bearings
A bearing chamber
193
Main lubrication system components are (7)
Oil pressure pumps
Scavenge pumps
Oil reservoir
Oil cooler/fuel heater
Filters
Magnetic chip detectors
Air/Oil separator
194
Labyrinth seal use ?
To prevent loss of oil from bearing housing
195
If you notice engine run down time has decreased, this means ?
There’s a damaged abradable lining/seal (grabbing abradable seal)
196
Pre flight lubrication checks
Oil quantity check - (sight glass)
Oil leaks - (walk around)
Shortly after engine start oil pressure should rise after 30 secs. If not may indicate a leak
197
What does rising oil quantity indicate ?
Fuel leaking into oil lube system
198
How is filter blockage indicated ?
CLOG
199
Smell of damp socks or acrid smoke may indicate ?
Internal engine issue
200
Purpose of engine fuel system ?
To provide fuel to the combustor at the correct pressure under all conditions
201
Fuel delivery is dependent on ?
Core rotation speed (N2)
202
FADEC stands for
Full Authority Digital Engine Control
203
Heart of the FADEC is a ?
Engine electronic controller (EEC), which has two channels for redundancy
204
FADEC power supplies ?
FADEC alternator/ generator - in flight
A/C electrical system - below 20% of N2 before and after
205
Major FADEC functions are
Deliver correct amount of fuel
Maintain sufficient HP pump output at low RPM
Fuel shut off when commanded
Overspeed protection
Controlling compressor airflow (BLD valves)
Ensuring manifold draining on shutdown
Reverse thrust
ACC
(Clue is F stands for Full ) Anything engine related
206
If you have a single channel failure ?
No loss of functionality, FADEC fault would be displayed
207
Dual channel failure ?
(Bank & PP answer is ) engine is will fail/ shutdown
( Mick says it will revert back to last selected power setting)
208
Jet fuel is a form of ?
Kerosene or parrafin oil
Most commonly Jet A and Jet A-1
(Jet A-1 has additives)
209
Jet A flash and waxing point ?
Flash +38°C
Waxing -40°C
210
Jet A-1 flash and waxing point
Flash point +38°C
Waxing point -47°C
211
Fuel additive blend is ?
Fuel system icing inhibitor (FSII)
Anti static additives
Oxidation and corrosion inhibitors
212
What fuel cane be used on cold climates (Canada, the poles) ?
Jet B
70% gasoline
30% kerosene
(Jet B is banned in Europe for commercial operations for safety and environmental concerns)
213
Fuel waxing ?
Fuel turns to a slushy substance and can CLOG all components within the system. Any water will for slush way before waxing point.
214
How is fuel starvation prevented ?
Fuel heater is now placed before the filters
215
De-rating means ?
The engine is set to have lower thrust in ideal conditions using less fuel.
However max thrust isn’t available if it becomes required
216
Flex thrust is ?
A temporary limitation on max thrust created by entering an assumed temperature which is higher than ambient, so engine produces less thrust saving fuel.
Max thrust (TO/GA) is available if required
217
How are de-rate and flex thrust set
By the crew via the CDU
218
Thrust may be indicated by ?
ratio of inlet to outlet pressure (EPR) or speed of the tan (N1)
219
Increase of vibration means ?
Trouble ahead
220
2 types of engine starter motor are ?
Air (pneumatic) starter - driven by compressed air
Electric (starter/generator) - driven by AC to start accessory gearbox, becomes a generator at ground idle.
221
Dry start
Low staggering RPM
No EGT
No fuel flow
- could be HPSOV malfunction
222
Hung start
Low staggering RPM
High EGT
Low fuel flow
- could be a compressor stall
- low bleed pressure
- engine failing to reach self sustaining speed
223
Hot start
Normal RPM increase
Rapid and excessive EGT rise
Normal fuel flow
-possible following a previous failed start attempt
224
Wet start
Low staggering RPM
No EGT
Some indicated fuel flow
- dry run should be carried out before re-trying
225
Multi engine spool start, difference in rotational speeds
N1- 20-25%
N2- 50-60%
226
Torching may result in ?
A tailpipe fire
This will not illuminate any warning
It may or may not be indicated by EGT
227
APU auto shutdown reasons
Fire warning
Excessive EGT
Low oil pressure
High oil temperature
Airspeed/Altitude limit exceeded
APU overspend
High bleed Air temperature
228
Typical APU capacity limits
Electrical power and Air bleed - 11’000ft
Air bleed - 17’000ft
Electrical power;
60KVA- 32’000 - 41’000ft
90KVA- sea level - 32’000ft
APU start up to - 41’000ft
Battery start not available above - 25’000ft
229
The APU supplies
Electrical and (optionally) pneumatic power
230
Starting sequence for an GTE on the ground ?
Starter, rotation, ignition, fuel
231
What is specific range in a jet aeroplane ?
Nautical miles flown per unit mass of fuel
232
Advantages of multi-spool engines ?
One smaller air starter driving only one spool can be used
233
In a GTE an un geared fan has the same RPM as ?
The low pressure compressor
234
What is the energy delivered by a free turbine DEPENDANT on ?
Rotational speed of the HP spool
235
Bypass ratio is the ratio of ?
Hot air mass flow to cold air mass flow
236
Converging duct induces ?
Decrease in pressure, increase in exhaust gas velocity
(pressure into speed)
237
