AGK Engines Flashcards
1
Q
What perfoms Ignition Timing and why is it important?
A
Performed by magnetos
Is necessary as it takes a finite time for the mixture to burn
2
Q
Which engine ignites combustion by the heat of compression?
A
Diesel 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
Induction Stroke
A
Inlet Valve opens just before TDC
Volume Increase
Pressure/Temp decrease
Inlet valve closes just before BDC
6
Q
Compression Stroke
A
Inlet/Exhaust valve closed
Stroke starts when piston is on the up
Volume decreases
Pressure/Temp increases
Just before TDC, mixture is ignited
7
Q
When is the mixture ignited and how?
A
Just before TDC
Spark plug - burns fuel instantaneously
8
Q
Power Stroke
A
Rapid rise in P/T
Inlet/Exhaust closed
Volume increases
Pressure/Temp decreases
Only stroke to produce POWER
9
Q
Exhaust Stroke
A
Starts at BDC, as piston begins to rise
Volume decrease
Pressure/Temp increase
Piston pushes out the waste gases
10
Q
Flame rate of aviation fuel mixed with air
A
60/80ft per second
11
Q
The cramk assembly is compromised of…
A
Crankshaft
Connecting rods
Pistons
12
Q
Hydraulic tappets are used to…
A
Automatically adjust the tappet clearance
13
Q
Why are valves often filled with sodium?
A
To take away heat
14
Q
Crank assembly
A
Connecting rods
Pistons
Crankshaft
15
Q
Name 4 EMF variables
A
Magnet size
Conductor length
Perpendicular angle
Rate of charge
16
Q
How long should the starter operating light take to switch off?
A
30 seconds
17
Q
An impulse coupling is…
A
Gives a higher energy retarded spark
18
Q
A high tension booster is…
A
A vibrartor directly connected to the high tension side (secondary circuit) and then Primary circuit
(Shower of sparks)
19
Q
A low tension booster
A
A set of pulses to the primary circuit
(Low tension side)
20
Q
Pre flight magneto checks are…
A
Drop Check
Dead Cut check
21
Q
What should happen if magneto check (Drop/Dead) reveals an issue?
A
Aircraft shut down
Fault logged in the AML
22
Q
RPM drop range on a DROP magneto check
A
Drop of 100-175rpm indicates normal magneto operation
Drop greater than 400rpm means there may be a faulty spark plug or p lead - report immediately!
23
Q
How to perform a Drop check
A
At 1000-1200rpm switch each magneto off in turn
Monitor for a drop in rpm and engine sound
Engine should continue to run
24
Q
What does a dead cut check ensure?
A
ignition switch circuit is operating correctly
Means engine can be shut down electrically
25
Should a DEAD cut check be performed before or after DROP check?
After and when engine is at 75%rpm (2000,2200rpm)
26
How to perform dead cut check
Ignition - switch OFF briefly
Engine rpm should rapidly decay (magnetos switched off)
ignition - switch ON before engine completely stops
27
If one magneto fails in flight, what happens?
None of the cylinders will stop firing
28
What powers the spark plugs during engine start up?
Magnetos
29
What converts continuous AC to a series of pulses?
Magneto
30
Design of ignition switch system...
Fail sake during flight
Allows engine to still fire even if switch fails
Potential hazard to anyone close to a stationary prop
31
What does a closed ignition switch do?
Grounds magneto and makes the ignition circuit safe
32
A blocked spark plug is said to be...
Fouled
33
A spark plugs body forms an...
Electrode
34
AVGAS is made up of?
15% carbon
85% hydrogen
35
An octane rating is
A measure of resistance to detonation
36
Detonation flame rate?
60-80 ft/s
37
What colour is AVGASLL?
Blue
Better for environment
38
What colour is AVGAS 100?
Green
Environmentally worse
39
What does LL stand for?
Low Led
40
What colour is AVGAS 80?
Red
Only for authorised certain aircraft
41
A fuel sample must be...
Clear and bright
Free of sediment
No entrained water
have a max water content of 30ppm
42
What does ppm stand for?
Parts per million
43
Causes of detonation...
Fuel with too low octane
incorrect (weak) mixture
Anything that could unduly raise temperature/pressure
High Engine temperature
44
Detonation flame rate?
1000ft/s
45
What is pre ignition?
Ignition of mixture before spark plug has fired
46
What causes Pre ignition?
Hot debris within cylinder (often carbon deposits)
Ignition malfunction (damaged spark plug)
High cylinder temp
47
Does detonation occur before or after pre ignition?
After
48
Mixture ratios
20:1 Lean (increased detonation risk)
15:1 Chemically correct (ideal ratio)
8:1 Rich ( increased detonation risk)
49
Takeoff mix
11:1
Rich mixture (for large power output), makes cylinder cooler
50
Cruise mix
17:1
Lean, it increases range
51
CHT and EGT
Cylinder head temp
Exhaust gas temp
52
How are mixture ratios measured?
By mass
53
Why does a 15:1 mix (ideal), create high CHT?
flame rate is slower, so is in contact with cylinder head for longer
54
What is Ineffective crank angle?
Period of relatively little movement of the piston around TDC and BDC
55
Inlet valve lag is when...
Inlet valve remains open just after BDC as the compression stroke begins
Helps fill chamber
Valve closes just after the piston leaves ineffective crank angle
56
Inlet valve lead is when...
Inlet valve open early, just before TDC (end off exhaust stroke)
Exhaust valves still open at the end of exhaust stroke
57
Exhaust valve lead is when...
E valve opens before BDC on P stroke
Longer time to clear cylinder waste gases
58
Exhaust valve Lag is when...
E valve is open until slightly after TDC
Remaining gases exit under own momentum
59
TDC
Top Dead Centre
60
BDC
Bottom Dead Centre
61
Where does valve overlap occur?
Around TDC between exhaust/induction strokes
62
What is Torque?
The capacity to do work (leverage)
ibs, ft, nm
63
Torque equation
Force (F) x Distance (D)
64
Force Equation
Pressure (P) x Area (M^2)
65
Piston Engine Principles
Chemical Energy
Heat Energy
Pressure Energy
Mechanical Energy
66
How to check health of engine?
Oil temp gauge
Oil Pressure gauge
CHT gauge
67
Secondary functions of engine oil?
Protect against corrosion
Cleaning engine
Cooling engine by absorbing heat and dissipating it to surrounding atmosphere
68
An ideal oil should be...
Discourages sludge formnation
Inhibits corrosion
Suitable viscosity over wide range of temps
69
Auxiliary spark augementation methods
Impulse coupling
Low tension booster
High Tension booster
70
Excessive engine cooling in a decent can cause damage to the engine, why?
Thermal shock
71
Impulse coupling components...
HUB CAM with flyweights
Spring
Shell (BODY)
72
73
Power Equation
Torque x RPM
74
What is the 'stroke'
Distance between TDC and BDC
75
How many degrees does the crank shaft rotate?
720 degrees
76
How many strokes in 1 cycle?
4
77
How many degrees does the crankshaft rotate between TDC and BDC
180 degrees
78
The ... rotates 1/2 speed of the crankshaft
Camshaft
79
What does a carburettor do?
Mixes fuel and air before it reaches the engine
80
What does CBP stand for?
Contact Breaker Point
81
'
82
What components seal the skirt rings?
Piston rings
83
What component lifts the push rods?
Cams
84
What does pressure do inside a carburettor?
Allows fuel to flow
85
Carb icing symptoms
Loss of rpm
Recued inlet MAP
Decreased EGT
Rough running
Jammed throttle
Engine stops
86
Carburettor alternative?
Fuel injection, fuel injected straight into cylinders
87
What is added to fuel to reduce detonation?
Lead
88
89
What is the pressure like inside the float chamber of a carburettor?
Atmospheric
90
RAM effect
When air is taken aboard an aircraft in flight, it undergoes an increase in pressure
91
Q
1/2 pV^2
92
Engine flywheel gear sequence
Starter motor
Starter overrun clutch
Flywheel gear
93
The higher compression ratio in a diesel engine means that the engine block has ... than similar powered petrol engine
Less weight
94
What do thick primary windings do in the magneto?
Create big pulses which are then sent to the spark plug
95
What does the CBP do?
Cuts the current at the peak and then goes back to zero and builds up again
96
What happens to the pressure on a cold engine start up?
Goes into the amber range on the gauge
~ This has to return to green before taxiing
97
Dry Sump Schematic
98
Liquid Cooling System
99
When is the cow flap opened and closed?
Closed during decent - otherwise cylinders will be over cooled
Opened during t/o to increase cooling
100
What should engine oil be?
Correct specification
Unopened bottle
101
What type of piston engine loses power during initial part of the climb to high altitude?
Normally aspirated
102
Where are intercoolers located?
Between turbocharger and inlet manifold
103
Waste gate principles...
Sensitive to ambient pressure
Controlled by waste gate controller
Controls rotational speed of the turbocharger
104
Oil pressure gauge
Oil temperature gauge
Measures oil pressure just after the oil filter
Measures oil temperature in oil return line
105
Where does a propeller make the most amount of thrust?
75% blade radius
106
Camber line and chord line are between?
Leading and trail edge
107
Does a petrol or diesel engine have a greater thermal efficiency?
Diesel
Higher compression ratio 20:1. But Petrol one has 10:1
108
What is the blade angel?
Angle in-between Chord line and Plane of Rotation
109
What is the most efficient AoA and when is it reached?
4 Degrees
Reached in the cruise
110
The effect of TAS on a fixed pitch propeller
As TAS increases, AoA decreases
As TAS decreases AoA increases
FYI, AoA is large at the start of T/O but as TAS increases, the propeller becomes more efficient
111
The effect of RPM on a fixed pitch propeller
As RPM increases, AoA increases
As RPM decreases, AoA decreases
112
Why are the Propeller blades twisted?
To preserve the AoA across the whole blade
Blade pitch angle must be reduced from root to tip
113
Effects on efficiency with different AoA
Optimum AoA (4 degrees) - Designed cruising speed (efficient)
High AoA - Higher than cruising speed (efficiency decreases)
Low AoA - Lower than causing speed (efficiency decreases)
114
What happens to the AoA if TAS increases/decreases in a Variable Pitch Propeller?
Stays the same
115
What happens to the AoA if RPM increases/decreases in a Variable Pitch Propeller?
Stays the same
116
Feathered, Coarse and Fine diagrams
117
What happens if ice forms on the spinner/propellers?
Anti ice system takes away the ice, either by,
Electrical heater system
Fluid dribbled over area
118
What does a reduction gearbox do?
Reduces RPM produced by propellers
119
What happens when forces are equal and opposite on a propeller assesmbly?
Stable propeller RPM can be achieved
120
What is a centrifugal twisting moment (CTM)
Each end of blade produce opposing moments
Counteracted by centrifugal weights at the blade root
Tendency to 'fine off'
Weights help at low RPM as centrifugal force drops off
121
What is Aerodynamic Twisting Moment (ATM)
Blade CP is ahead of the pitch change axis
Aerodynamic force generates a movement around the axis point driving the propeller towards coarse
122
Which is more dominant, CTM or ATM and why?
CTM is more dominant because...
Wind milling prop causes both actions to combine - prop drives to fine due to increased drag
123
SEP...
MEP...
PCU...
Single Engine Piston
Multi Engine Piston
Propeller Control Unit
124
If propeller control lost, why is it better for the props to be in the 'fine' position?
Can land/GA
Incraese airflow round the props, increase in thrust if it were to turn back on
125
Change in exhaust back pressure causes...
Increase in volumetric efficiency
126
What does FADEC reduce?
Number of controls In cockpit
Engine handling task
127
On a constant speed prop, excessive power demand may be indicated by...
Boost warning light
128
If you increase power substantially, the overboots warning light will come onion you don't adjust the...
RPM Lever
129
High SFC indicates...
Poor efficiency
130
On a constant speed prop, phrase for throttle and RPM lever relationship is
'Rev up - throttle back'
131
On a petrol engine, mixture adjustment can be finessed by referring to...
EGT gauge
132
For a fixed pitch prop at any alt, increasing RPM does what to the power output?
Increases power output
133
On a petrol engine, lean mixture required in the cruise is set using the...
Mixture control lever
134
On a constant speed prop, power is indicated by MAP and
Torgue gauge
135
On a fixed pitch prop, power is approx indicts by
RPM gauge
136
On a constant speed prop, power is estimated by meaning MAP in the ... and/ or by meaning the ...
Manifold
EGT
137
FADEC stands for...
Full Authority digital engine control
138
Can carburettor engines ben fitted with FADEC?
No
139
Does oil temp increase in the climb with a low speed and high power?
Study increase in oil temp
