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XAGK > Powerplant lesson 2 > Flashcards

Powerplant lesson 2 Flashcards

1
Q

In theory, when does combustion happen?

A

TDC power stroke

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2
Q

When does combustion happen in practice?

A

Spark plug fires just before TDC

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3
Q

What’s the name for the process where valves operate early/late?

A

valve lead
valve lag
valve overlap

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4
Q

How does enough time get left for the valves to open and close?

A

value lead
valve lag
valve overlap

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5
Q

What is ineffective crank angle?

A

The top 90 and bottom 90

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6
Q

Power =

A

Power = Torque x RPM

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7
Q

Torque =

A

Torque = Force x distance

Distance is the distance from centre of crank to the crank pin.

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8
Q

Force =

A

force = pressure x area

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9
Q

Area is equal to which engine component

A

Piston crown

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10
Q

What is the only thing you can change in the power = torque x RPM

A

Throttle! This changes the air component which changes the air pressure.
This creates more power.

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11
Q

What is the name of the cycle where charge is drawn into the cylinder.

A

Induction

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12
Q

When the piston drops volume increases meaning that pressure _________?

A

Decreases

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13
Q

What word means chemically balanced.

A

Stoichiometric
(chemically balanced)

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14
Q

What is the ideal ratio of air to fuel (mass) AFR?

A

15:1

15 parts of air
1 part fuel

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15
Q

Engine pressure is always lower than atmosphere!
True/flase

A

True

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16
Q

What is the name of the engine cycle where the piston moves upwards (not exhaust)

A

compression

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17
Q

What is the danger through the compression phase?

A

Detonation as the pressure and temperature increases.

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18
Q

How would you describe the difference in pressure from atmosphere to the carburettor venturi.

A

Lower pressure in the venturi

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19
Q

The U-Tube is in which component?

A

Carburettor

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20
Q

U-Tube has fuel sitting in the bottom because of.

A

Gravity and equal atmospheric pressure on either side.

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21
Q

As the throttle opens, more air comes in. Describe what happens with the fuel.

A

As more air comes in, the lower the pressure in the venturi and the more fuel gets sucked in.

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22
Q

In a climb, without any change, what happens to the mixture

A

Becomes richer in the climb

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23
Q

Describe a pressure balance duct.

A

U-tube connected back to the (pre-venturi) intake.

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24
Q

What feature helps reduce the issue of a richer mixture in the climb?

A

pressure balance duct

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25
Q

The pressure balance duct helps correct for changes in which speed?

A

TAS
Altitude

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26
Q

Where does the ‘main jet’ sit and what does it do?

A

A narrowing of the tube to venturi to control flow.

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27
Q

Throttle sits upstream or downstream of the venturi?

A

downstream

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28
Q

What does an atomiser do and where does it sit

A

The atomiser sits in/just before the venturi and turns the fuel delivery into a vapour.

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29
Q

Liquid fuel doesn’t burn. What does?

A

Vapour

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30
Q

What is the diffuser and where does it sit?

A

Physically, after or parallel the main jet.
It balances fuel flow to speed and O2 levels

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31
Q

What is another name for a diffuser?

A

Emulsification tube

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32
Q

The diffuser (emulsifier) takes a static pressure feed and it’s job is?

A

Add air bubbles to the mixture

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33
Q

The straw in a glass drawing explains which component?

A

The diffuser (emulsifier)

More static pressure means the fuel sits lower, so fewer holes are submerged and there is less fuel added to the mixture

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34
Q

In which part is the mixture control applied?

A

The diffuser (emulsifier)

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35
Q

The mixture control over rides which component?

A

Diffuser. It intercepts the static intake and adjusts the pressure by bleeding to atmosphere.

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36
Q

Lycoming mixture graph which two lines are parallel?

A

EGT and CHT

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37
Q

CHT is measured from which cylinder?

A

Hottest cylinder

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38
Q

Lycoming mixture graph. What is the ratio at the top of the curve?

A

15 : 1

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39
Q

Fuel cooled / rich mixture. How does it cool the engine?

A

As the fuel is diffused it absorbs the heat of the engine.

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40
Q

What are the guide ratios for mixture?

A

9:1 starting
12:1 take off
14:1 climb
17:1 power cruise
19:1 economy cruise

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41
Q

The rich . lean graph.. what should you pay attention to?

A

Rich, lean scale. Which way around is it?

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42
Q

What is the name of the component that prevents lean cut?

A

Accelerator pump

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43
Q

The accelerator can also have a secondary function. What is it?

A

priming (3 pumps)

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44
Q

In a high performance aircraft you can have a component that will provide a rich mixture to cool the engine at high RPM / power settings.

A

Boost pump - manually triggered

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45
Q

What are the methods of priming

A

Accelerator pump
Priming hand pump - lock after use
electric pump (auto)

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46
Q

Where is the carb located physically on a lycoming engine?

A

Underneath

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47
Q

Beneath the carb is the?

A

air intake

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48
Q

What kind of temperature drop would you expect in a carb?

A

25deg c

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49
Q

What conditions are you likely to find carb icing

A

visible moisure

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50
Q

What is the expected loss in power using carb heat?

A

15% loss in power

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51
Q

What are the potential issues with carb heat use?

A

Unfiltered air
15% power loss
Can create the icing conditions
Increase detonation risk

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52
Q

What is the name for the icing within a Carb

A

refrigeration icing

caused by lower temperature and fuel evaporation.

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53
Q

What is the name for icing at the air intake.

A

Impact icing

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54
Q

Fuel injection doesn’t require a venturi so there isn’t a risk of

A

carb icing
(there is still impact ice)

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55
Q

An injected engine is missing ‘carb heat’ what is it replaced with?

A

Alternate air

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56
Q

Injected engines are missing a few controls, what are they?

A

No mixture
no priming
no carb heat

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57
Q

Injected engines have a fuel pump which leads to which 4 things?

A

Manifold valve
metering valve
mixture valve
distribution valve

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58
Q

Injected engines have an extra switch. What is it

A

Fuel pump
Alternative air

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59
Q

The air in an injected or carburetted system is the same. Where is the fuel injected.

A

Either directly into the cylinder or after the butterfly.

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60
Q

The manifold valve is seen in which type of engine

A

Injected

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61
Q

When is the fuel pump on?

A

Startup and in critical phases of flight

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62
Q

What type of injectors do aircraft have?

A

Electronic solenoid injectors

63
Q

Why the lead?

A

Temperature
Lubrication
valve strength

64
Q

Difference between AVGAS and MOGAS

A

Water content.
AVGAS is regulated at max 20ppm

65
Q

Can you use 80 fuel in an aircraft requiring 100

A

No

66
Q

Can you use 100 fuel in an aircraft requiring 80

A

Yes, for short periods

67
Q

What colour is found in 100ll fuel

A

blue

68
Q

What colour is found in 100 fuel

A

green

69
Q

What colour is found in 80 fuel

A

red

70
Q

What colour is found in 82 unleaded fuel

A

purple

71
Q

Purpose of lubrication (4)

A

Lubricate
Clean
Cool (control expansion)
Perform hydraulic functions (prop pitch)

72
Q

Oil properties

A

Viscosity
Resistance to flow
thickness

73
Q

Oil options (3)

A

Synthetic
semi-synthetic
Mineral

74
Q

Synthetic oil allows Viscosity to get _______ as the engine gets hotter.

A

Thicker
Viscosity is closely controlled

75
Q

Oil grades: what does W10 mean

A

At 15deg C, the oil will take 10 time as long as water to trickle down 45deg glass

76
Q

What does 10W50

A

Viscosity increases as temperature increases.
Behaves like a 10 when cold and 50 when warm.

77
Q

Do we mix oils?

A

Best not, but use the correct oil

78
Q

What should you look for in an oil container?

A

Clean
labelled
sealed

79
Q

Two types of oil system are?

A

Dry sump
Wet sump

80
Q

Aerobatic and high altitude aircraft would favour what kind of oil system?

A

Dry sump

81
Q

Standard aero system would be which oil system?

A

Wet sump

82
Q

Describe the dry sump

A

Dedicated oil reservoir
has a scavenger pump
Sight glass
Dipstick

83
Q

Describe the wet sump

A

No reservoir
Oil is stored in sump

84
Q

What is inside a drysump reservoir?

A

Fins and baffles to stop liquid moving about

85
Q

Downstream of a drysump reservoir is?

A

Non-return valve (check valves)
Main pressure pump
Non-return valve (NRV)
Pressure relief vale (PRV)
Oil filter
Engine
De-aeration / de-forming plate

86
Q

Normal oil pressure is?

A

4.5 bar / 75psi

87
Q

What happens if the oil filter gets blocked or the oil is cold?

A

There is a bypass that senses pressure difference.

88
Q

What indications are there on the dry sump oil system?

A

Clog (on filter bypass)
Oil pressure
Oil quantity

89
Q

Oil gets sent to specific location of the engine. What is this system called?

A

Pressure feeds

90
Q

What ensured the dry sump stays dry?

A

Powerful scavenge pump driven by crank shaft.

91
Q

Where does the oil go after the engine in a dry sump system?

A

Oil cooler.
(also has a bypass)

92
Q

In a dry sump, oil gets returned to the reservoir. Where was it before the reservoir?

A

Oil cooler

93
Q

There is a magnet in the oil system. What is it for?

A

Chip detectors to collect any ferrous metal debris.
(the location can vary)
Pistons are aluminium so won’t get picked up.

94
Q

When do you check the oil level on a dry sump oil system?

A

While the engine is running!!

95
Q

Where is the oil stored in a wet sump system?

A

In the sump

96
Q

Wet sump is missing an oil cooler so it compensates by doing what?

A

3 times as much oil

97
Q

Oil pump sits above the oil level on which component?

A

Crankshaft

98
Q

The oil pump collects from where?

A

Wet sump

99
Q

The oil pump pushes out the engine to which components before re-entering the engine?

A

Pressure relief valve
Filter (and bypass)
optional cooler

100
Q

If fitted, where would the cooler be fitted on a wet sump system.

A

Feed line - just before re-entering the engine

101
Q

Where would you measure oil pressure?

A

After the pressure release valve

102
Q

Where would you measure oil temperature?

A

After the cooler (if fitted).

103
Q

Pumps produce?

A

Flow

104
Q

Pressure is produced when you ______ flow

A

resist

105
Q

What are the two methods to keep an engine cool?

A

Air
Liquid (water/antifreeze)

106
Q

What component regulates the temperature in a water-cooled system?

A

Thermostat

107
Q

What physical process means that cool water is brought into the bottom of the system?

A

The heater water rises
(Thremo syphon)
But a water pump helps it too.

108
Q

Temperature range is:

A

88 - 92

109
Q

The pressurised system 15psi means that the boiling point changes in which direction?

A

Boiling point is now higher (about 140degc)

110
Q

Expansion tank (containing coolant) needs checking it’s between the high and low. How hot should it be.

A

40deg C
cool enough to the touch

111
Q

Air cooling relies on what in the engine to direct incoming air around the cylinders?

A

Baffles / air scoops

112
Q

What do cowl flaps do?

A

Regulate the airflow around the engine.
They are adjusted inflight and on the ground.

113
Q

Examples of power augmentation

A

Turbo
supercharger

114
Q

Turbo and super are there to do what?

A

Delay the onset of power loss by forcing pressurised air into the engine

115
Q

MAP is short for

A

Manifold Absolute Pressure

116
Q

Manifold cylinder pressure =

A

cylinder pressure

117
Q

More air + more fuel =

A

more power

118
Q

MAP guage lives where and measures what?

A

After the carburettor, before the cylinders
It measures ALL the contents going into the engine.

119
Q

Manifold cylinder pressure gauge is what type of guage

A

Vacuum

120
Q

1013Hpa =

A

29.92inHG

121
Q

What’s the maximum pressure we can get into an engine with the throttle wide open?

A

Atmospheric pressure

122
Q

Idle speed is ___est manifold air pressure

A

lowest

123
Q

Throttle opened is ____est mainfold air pressure

A

highest

124
Q

Maniford air pressure guage will show what when the engine is off (masters on)

A

QFE - atmospheric

125
Q

Why would Manifold pressure never be QFE?

A

The engine wouldn’t work as no air would be pulled into the cylinder

126
Q

Aircraft service ceiling is define by

A
127
Q

Aircraft performance ceiling is defined by what (using MAP)

A

When atmospheric pressure = manifold air pressure

128
Q

In a constant MAP climb, what happens to power

A

Increases until performance ceiling

129
Q

What instrument is common with a super or turbo charger?

A

Boost gauge

130
Q

On a boost gauge what are the two sides?

A

Augmented boost
MAP side

131
Q

As you climb, a boost gauge will do what?

A

Decrease until the critical altitude when the turbo/super isn’t working any more.

132
Q

Two types of supercharger are?

A

Ground boosted
Altitude boosted

133
Q

Describe a ground boosted supercharger

A

Boost from sea level
decrease with increasing altitude

134
Q

Describe a altitude boosted supercharger

A

boosts above a given altitude
MAP at sea level
calibrated to a specific pressure

135
Q

How is a turbocharger driven?

A

exhaust gas

136
Q

How is a supercharger driven

A

crankshaft
it’s a parasitic load taking some power from the engine

137
Q

What part of a turbo helps prevent detonation

A

Charge air cooler (outputs at about 25 deg)

138
Q

In a turbo there are two components on a single shaft. What are they?

A

Compressor and turbine

139
Q

In a turbo, the exhaust leaves the engine and hits a controller called the _____ ____ that sits after the engine

A

waste gate

140
Q

After the waste gate, the exhaust proceeds to the

A

Turbine

141
Q

The shaft in a turbine spins very quickly so the brass bearings need a fresh feed of

A

Oil, direct from the oil pump.

142
Q

The waste gate in a turbo can direct flow in two directions in any proportion. What are the two directions?

A

Turbine
Atmosphere

143
Q

What controls the wastegate?

A

oil pressure controlled by a capsule

144
Q

If the engine is off, what position is the wastegate in?

A

Open (to atmosphere)

145
Q

If the engine is idling, what position is the wastegate in?

A

Almost closed

146
Q

If we are taking off, what position is the wastegate in?

A

Partially open

147
Q

If climb to out ceiling, what position is the wastegate in?

A

Closing (Turbine)

148
Q

If we are at our performance ceiling what position is the wastegate in?

A

Fully closed

149
Q

In a decent, what position is the wastegate in?

A

opening

150
Q

What is an overboost safety valve?

A

Sits between engine and waste gate as a fail safe.

151
Q

Smooth throttle operation is required when using what?

A

Turbo and super chargers

152
Q

How long should you idle a turbocharged engine before shutting down?

A

3 - 5 mins

153
Q
A

XAGK (17 decks)

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