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Groundschool : Module 1 > AGK Engines > Flashcards

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

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2
Q

Which engine ignites combustion by the heat of compression?

A

Diesel Engine

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3
Q

Which engine uses a spark to initiate ignition

A

Petrol Engine

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4
Q

Name the strokes in a 4 stroke engine

A

Induction, Compression, Power, Exhaust

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5
Q

Induction Stroke

A

Inlet Valve opens just before TDC
Volume Increase
Pressure/Temp decrease
Inlet valve closes just before BDC

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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

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7
Q

When is the mixture ignited and how?

A

Just before TDC
Spark plug - burns fuel instantaneously

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8
Q

Power Stroke

A

Rapid rise in P/T
Inlet/Exhaust closed
Volume increases
Pressure/Temp decreases
Only stroke to produce POWER

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9
Q

Exhaust Stroke

A

Starts at BDC, as piston begins to rise
Volume decrease
Pressure/Temp increase
Piston pushes out the waste gases

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10
Q

Flame rate of aviation fuel mixed with air

A

60/80ft per second

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11
Q

The cramk assembly is compromised of…

A

Crankshaft
Connecting rods
Pistons

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12
Q

Hydraulic tappets are used to…

A

Automatically adjust the tappet clearance

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13
Q

Why are valves often filled with sodium?

A

To take away heat

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14
Q

Crank assembly

A

Connecting rods

Pistons

Crankshaft

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15
Q

Name 4 EMF variables

A

Magnet size
Conductor length
Perpendicular angle
Rate of charge

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16
Q

How long should the starter operating light take to switch off?

A

30 seconds

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17
Q

An impulse coupling is…

A

Gives a higher energy retarded spark

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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)

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19
Q

A low tension booster

A

A set of pulses to the primary circuit
(Low tension side)

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20
Q

Pre flight magneto checks are…

A

Drop Check
Dead Cut check

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21
Q

What should happen if magneto check (Drop/Dead) reveals an issue?

A

Aircraft shut down
Fault logged in the AML

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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!

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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

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24
Q

What does a dead cut check ensure?

A

ignition switch circuit is operating correctly
Means engine can be shut down electrically

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25
Q

Should a DEAD cut check be performed before or after DROP check?

A

After and when engine is at 75%rpm (2000,2200rpm)

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26
Q

How to perform dead cut check

A

Ignition - switch OFF briefly
Engine rpm should rapidly decay (magnetos switched off)
ignition - switch ON before engine completely stops

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27
Q

If one magneto fails in flight, what happens?

A

None of the cylinders will stop firing

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28
Q

What powers the spark plugs during engine start up?

A

Magnetos

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29
Q

What converts continuous AC to a series of pulses?

A

Magneto

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30
Q

Design of ignition switch system…

A

Fail sake during flight

Allows engine to still fire even if switch fails

Potential hazard to anyone close to a stationary prop

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31
Q

What does a closed ignition switch do?

A

Grounds magneto and makes the ignition circuit safe

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32
Q

A blocked spark plug is said to be…

A

Fouled

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33
Q

A spark plugs body forms an…

A

Electrode

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34
Q

AVGAS is made up of?

A

15% carbon
85% hydrogen

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35
Q

An octane rating is

A

A measure of resistance to detonation

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36
Q

Detonation flame rate?

A

60-80 ft/s

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37
Q

What colour is AVGASLL?

A

Blue
Better for environment

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38
Q

What colour is AVGAS 100?

A

Green
Environmentally worse

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39
Q

What does LL stand for?

A

Low Led

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40
Q

What colour is AVGAS 80?

A

Red
Only for authorised certain aircraft

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41
Q

A fuel sample must be…

A

Clear and bright
Free of sediment
No entrained water
have a max water content of 30ppm

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42
Q

What does ppm stand for?

A

Parts per million

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43
Q

Causes of detonation…

A

Fuel with too low octane
incorrect (weak) mixture
Anything that could unduly raise temperature/pressure
High Engine temperature

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44
Q

Detonation flame rate?

A

1000ft/s

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45
Q

What is pre ignition?

A

Ignition of mixture before spark plug has fired

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46
Q

What causes Pre ignition?

A

Hot debris within cylinder (often carbon deposits)
Ignition malfunction (damaged spark plug)
High cylinder temp

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47
Q

Does detonation occur before or after pre ignition?

A

After

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48
Q

Mixture ratios

A

20:1 Lean (increased detonation risk)
15:1 Chemically correct (ideal ratio)
8:1 Rich ( increased detonation risk)

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49
Q

Takeoff mix

A

11:1
Rich mixture (for large power output), makes cylinder cooler

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50
Q

Cruise mix

A

17:1
Lean, it increases range

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51
Q

CHT and EGT

A

Cylinder head temp
Exhaust gas temp

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52
Q

How are mixture ratios measured?

A

By mass

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53
Q

Why does a 15:1 mix (ideal), create high CHT?

A

flame rate is slower, so is in contact with cylinder head for longer

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54
Q

What is Ineffective crank angle?

A

Period of relatively little movement of the piston around TDC and BDC

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55
Q

Inlet valve lag is when…

A

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

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56
Q

Inlet valve lead is when…

A

Inlet valve open early, just before TDC (end off exhaust stroke)
Exhaust valves still open at the end of exhaust stroke

57
Q

Exhaust valve lead is when…

A

E valve opens before BDC on P stroke
Longer time to clear cylinder waste gases

58
Q

Exhaust valve Lag is when…

A

E valve is open until slightly after TDC
Remaining gases exit under own momentum

59
Q

TDC

A

Top Dead Centre

60
Q

BDC

A

Bottom Dead Centre

61
Q

Where does valve overlap occur?

A

Around TDC between exhaust/induction strokes

62
Q

What is Torque?

A

The capacity to do work (leverage)
ibs, ft, nm

63
Q

Torque equation

A

Force (F) x Distance (D)

64
Q

Force Equation

A

Pressure (P) x Area (M^2)

65
Q

Piston Engine Principles

A

Chemical Energy
Heat Energy
Pressure Energy
Mechanical Energy

66
Q

How to check health of engine?

A

Oil temp gauge

Oil Pressure gauge

CHT gauge

67
Q

Secondary functions of engine oil?

A

Protect against corrosion

Cleaning engine

Cooling engine by absorbing heat and dissipating it to surrounding atmosphere

68
Q

An ideal oil should be…

A

Discourages sludge formnation

Inhibits corrosion

Suitable viscosity over wide range of temps

69
Q

Auxiliary spark augementation methods

A

Impulse coupling
Low tension booster
High Tension booster

70
Q

Excessive engine cooling in a decent can cause damage to the engine, why?

A

Thermal shock

71
Q

Impulse coupling components…

A

HUB CAM with flyweights
Spring
Shell (BODY)

72
Q
A
73
Q

Power Equation

A

Torque x RPM

74
Q

What is the ‘stroke’

A

Distance between TDC and BDC

75
Q

How many degrees does the crank shaft rotate?

A

720 degrees

76
Q

How many strokes in 1 cycle?

A

4

77
Q

How many degrees does the crankshaft rotate between TDC and BDC

A

180 degrees

78
Q

The … rotates 1/2 speed of the crankshaft

A

Camshaft

79
Q

What does a carburettor do?

A

Mixes fuel and air before it reaches the engine

80
Q

What does CBP stand for?

A

Contact Breaker Point

81
Q
A

’

82
Q

What components seal the skirt rings?

A

Piston rings

83
Q

What component lifts the push rods?

A

Cams

84
Q

What does pressure do inside a carburettor?

A

Allows fuel to flow

85
Q

Carb icing symptoms

A

Loss of rpm

Recued inlet MAP

Decreased EGT

Rough running

Jammed throttle

Engine stops

86
Q

Carburettor alternative?

A

Fuel injection, fuel injected straight into cylinders

87
Q

What is added to fuel to reduce detonation?

A

Lead

88
Q
A
89
Q

What is the pressure like inside the float chamber of a carburettor?

A

Atmospheric

90
Q

RAM effect

A

When air is taken aboard an aircraft in flight, it undergoes an increase in pressure

91
Q

Q

A

1/2 pV^2

92
Q

Engine flywheel gear sequence

A

Starter motor
Starter overrun clutch
Flywheel gear

93
Q

The higher compression ratio in a diesel engine means that the engine block has … than similar powered petrol engine

A

Less weight

94
Q

What do thick primary windings do in the magneto?

A

Create big pulses which are then sent to the spark plug

95
Q

What does the CBP do?

A

Cuts the current at the peak and then goes back to zero and builds up again

96
Q

What happens to the pressure on a cold engine start up?

A

Goes into the amber range on the gauge
~ This has to return to green before taxiing

97
Q

Dry Sump Schematic

A
98
Q

Liquid Cooling System

A
99
Q

When is the cow flap opened and closed?

A

Closed during decent - otherwise cylinders will be over cooled
Opened during t/o to increase cooling

100
Q

What should engine oil be?

A

Correct specification
Unopened bottle

101
Q

What type of piston engine loses power during initial part of the climb to high altitude?

A

Normally aspirated

102
Q

Where are intercoolers located?

A

Between turbocharger and inlet manifold

103
Q

Waste gate principles…

A

Sensitive to ambient pressure

Controlled by waste gate controller

Controls rotational speed of the turbocharger

104
Q

Oil pressure gauge

Oil temperature gauge

A

Measures oil pressure just after the oil filter

Measures oil temperature in oil return line

105
Q

Where does a propeller make the most amount of thrust?

A

75% blade radius

106
Q

Camber line and chord line are between?

A

Leading and trail edge

107
Q

Does a petrol or diesel engine have a greater thermal efficiency?

A

Diesel

Higher compression ratio 20:1. But Petrol one has 10:1

108
Q

What is the blade angel?

A

Angle in-between Chord line and Plane of Rotation

109
Q

What is the most efficient AoA and when is it reached?

A

4 Degrees

Reached in the cruise

110
Q

The effect of TAS on a fixed pitch propeller

A

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
Q

The effect of RPM on a fixed pitch propeller

A

As RPM increases, AoA increases

As RPM decreases, AoA decreases

112
Q

Why are the Propeller blades twisted?

A

To preserve the AoA across the whole blade

Blade pitch angle must be reduced from root to tip

113
Q

Effects on efficiency with different AoA

A

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
Q

What happens to the AoA if TAS increases/decreases in a Variable Pitch Propeller?

A

Stays the same

115
Q

What happens to the AoA if RPM increases/decreases in a Variable Pitch Propeller?

A

Stays the same

116
Q

Feathered, Coarse and Fine diagrams

A
117
Q

What happens if ice forms on the spinner/propellers?

A

Anti ice system takes away the ice, either by,

Electrical heater system

Fluid dribbled over area

118
Q

What does a reduction gearbox do?

A

Reduces RPM produced by propellers

119
Q

What happens when forces are equal and opposite on a propeller assesmbly?

A

Stable propeller RPM can be achieved

120
Q

What is a centrifugal twisting moment (CTM)

A

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
Q

What is Aerodynamic Twisting Moment (ATM)

A

Blade CP is ahead of the pitch change axis

Aerodynamic force generates a movement around the axis point driving the propeller towards coarse

122
Q

Which is more dominant, CTM or ATM and why?

A

CTM is more dominant because…

Wind milling prop causes both actions to combine - prop drives to fine due to increased drag

123
Q

SEP…

MEP…

PCU…

A

Single Engine Piston

Multi Engine Piston

Propeller Control Unit

124
Q

If propeller control lost, why is it better for the props to be in the ‘fine’ position?

A

Can land/GA

Incraese airflow round the props, increase in thrust if it were to turn back on

125
Q

Change in exhaust back pressure causes…

A

Increase in volumetric efficiency

126
Q

What does FADEC reduce?

A

Number of controls In cockpit

Engine handling task

127
Q

On a constant speed prop, excessive power demand may be indicated by…

A

Boost warning light

128
Q

If you increase power substantially, the overboots warning light will come onion you don’t adjust the…

A

RPM Lever

129
Q

High SFC indicates…

A

Poor efficiency

130
Q

On a constant speed prop, phrase for throttle and RPM lever relationship is

A

‘Rev up - throttle back’

131
Q

On a petrol engine, mixture adjustment can be finessed by referring to…

A

EGT gauge

132
Q

For a fixed pitch prop at any alt, increasing RPM does what to the power output?

A

Increases power output

133
Q

On a petrol engine, lean mixture required in the cruise is set using the…

A

Mixture control lever

134
Q

On a constant speed prop, power is indicated by MAP and

A

Torgue gauge

135
Q

On a fixed pitch prop, power is approx indicts by

A

RPM gauge

136
Q

On a constant speed prop, power is estimated by meaning MAP in the … and/ or by meaning the …

A

Manifold

EGT

137
Q

FADEC stands for…

A

Full Authority digital engine control

138
Q

Can carburettor engines ben fitted with FADEC?

A

No

139
Q

Does oil temp increase in the climb with a low speed and high power?

A

Study increase in oil temp

Groundschool : Module 1 (38 decks)

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