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Aviation > CPL AGK > Flashcards

CPL AGK Flashcards

1
Q

Radial engines have great power to weight ratios, however they….

A

Have a large frontal area, and thus produce large amounts of drag

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2
Q

Inline inverted engines are designed to

A

Give the prop clearance from the ground (and also to increase forward visibility)

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3
Q

The more cylinders there are….

A

the smoother the engine runs (due to more constant power strokes)

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4
Q

Compression ratio=

A

Total volume of cylinder/clearance volume

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5
Q

What are the units/values for 1 horsepower

A

33000 foot pounds/minute
550 foot pounds/second
0.746 kW

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6
Q

What is indicated horsepower

A

Pure power generated from the engine

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7
Q

What is friction horespower

A

Horsepower loss due to frictional forces inside the engine

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8
Q

HP

A

BHP=IHP-FHP

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9
Q

volumetric efficiency=

A

amount of cht of charge (by weight) in cylinder @ standard temperature and pressure arge in cylinder (by weight)/Maximum amoun

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10
Q

What is a typical volumetric efficiency

A

70%-80%

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11
Q

What is thermal efficiency?

A

Ratio of power actually delivered by the engine to the power theoretically available in the fuel

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12
Q

What is a typical thermal efficiency value

A

30%

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13
Q

when the engine is off, what should the manifold pressure read

A

atmospheric pressure

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14
Q

How are magnetos powered?

A

Engine driver

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15
Q

What is engine kickback

A

When the spark occurs too early and causes the crankshaft is pushed in the wrong direction (this is why we need impulse coupling to delay the spark, as this phenomenom often occurs at low rpm)

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16
Q

Why do we only use the left magneto on startup

A

because only 1 spark plug is required on start up

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17
Q

What does the distributor in an ignition system do

A

distributes the current to the different spark plugs

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18
Q

What is a “dead-cut check”

A

A check whereby the magnetos are checked if they are earthing or not

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19
Q

What does the accelerator pump in a carby system provide

A

Additional mixture when the throttle is opened rapidly in order to avoid power lag.

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20
Q

What does the enrichment valve do

A

provides additional fuel at <75% power settings to aid in cooling

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21
Q

What is the idling jet for?

A

Used to provide fuel when the throttle is almost closed at low rpms (is positioned after the throttle bautterfly for this purpose

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22
Q

What are the conditions for carby icing

A

<50% humidity and around 35 degrees celcius

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23
Q

What is impact ice

A

Supercooled water droplets in the intake impact on metal surfaces and then freeze

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24
Q

What is fuel icing

A

Vaporisation of fuel causing a temperature drop which causes water to precipitate which will then freeze onto surfaces

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25
Q

What is throttle icing

A

Air that accelerates decreases in temperature

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26
Q

In what conditions is throttle icing most likely to occur

A

greatest at low power settings

-10 to 20 degrees celcius with a high relative humidity

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27
Q

What are some of the advantages of fuel injection systems

A

No fuel icing
More efficient
Fewer maintenance problems
Faster acceleration response

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28
Q

What are some of the disadvantages of fuel injection systems

A

Vapour locks
More susceptible to contamination (due to having thin lines)
Fuel that goes through return lines may be vented overboard if the tank it is being delivered to is full

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29
Q

What are the purposes of oil

A

clean, cool, lubricate, protect, seal

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30
Q

Why is straight mineral oil used for the first 50ish hours of engine life?

A

Because it allows the surfaces to rub together and create their own fit

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31
Q

Why do we prefer ashless dispersant oil in general use

A

Because it doesn’t possess the carbon-forming characteristics of mineral oil, and it prevents sludge from forming (therefore less oil blocks)

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32
Q

Why are synthetic oils so good?

A

Because they have been designed to operate at a large variety of temperatures and altitudes

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33
Q

Can you mix aircraft oil types?

A

yes (although take caution with mixing of synthetic oils due to lack of data on effects)

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34
Q

Can we use motor oils in planes?

A

No

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35
Q

How can we tell that an aircraft is burning oil?

A

Rich blue smoke is coming out of the exhaust

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36
Q

Oil consumption is a good indication of….

A

engine health

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37
Q

Commercial aviation oil number is what compared to the SAE oil number

A

2 times

e.g. aviation=80 but SAE=40

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38
Q

What is the approximate specific gravity of piston airplane oil

A

0.9

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39
Q

Why does oil need to be changed reguarly

A

oxidation and water absorption

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40
Q

Describe the oil system typical of most light aircraft

A

Wet-sump
stores oil in a collector tank
gravity dependent (although does have a pump)
Incorporates pressure relieve valve to prevent against excessive pressure

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41
Q

Describe the oil system typical of aerobatic aircraft

A

Dry-sump
Uses a scavenge pump to attain oil from an external tank
Due to the pump systems, inverted flight is possible

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42
Q

give some reasons as to low oil pressure

A

low qty
leak in the oil lines/tank
failure of the oil pump
oil pressure relief valve stuck open

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43
Q

Are pressure gauges reliable?

A

Not all instruments are reliable, and so it is important to crosscheck with other instruments in order to deduce the issue, as using multiple data sources should result in more accurate interpretation

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44
Q

What is supercharging

A

artificially increasing the pressure available to the intake manifold. the more air=more fuel=bigger boom=more power

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45
Q

Differentiate between a supercharger and a turbocharger

A

supercharger=compressor is controlled by the mechanical gears of the engine. Turbocharger uses exhaust gases to turn a turbine which turns a compressor.

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46
Q

How does a supercharger increase pressure

A

Air is forced out from the impeller, gains kinetic energy and flows out through diffuser vanes, this kinetic energy is then converted into an approximate 50% increase in pressure

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47
Q

What are the factors that influence how much pressure a supercharger will develop

A

RPM
Diameter of impeller
Shape of impeller blades
Shape of diffuser vanes

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48
Q

Where is the carby placed in a supercharger system and why?

A

Just before the inlet so as to aid in cooling so that the air doesn’t heat up too much

49
Q

Current superchargers can maintain sea level pressure up to what altitude

A

10,000ft

50
Q

Define full throttle height

A

The maximum height at which a supercharger is able to provide sea level pressure

51
Q

What happens above full throttle height

A

Aircraft behaves like a normally aspirated engine, and a decrease in performance occurs as the aircraft climbs higher and higher

52
Q

Why do we see an INCREASE in the volumetric efficiency as we climb higher?

A

Because of the reduced pressure differential, exhaust gases are able to flow out more efficiently.

53
Q

What RPM is full throttle height

A

Each rpm setting has a corresponding full throttle height

54
Q

How does the supercharger protect against overboosting

A

The throttle valve will not open fully unless the aircraft is at or above full throttle height

55
Q

Give some reasons as to why turbochargers are more efficient that superchargers

A

Turbos don’t lose power due to the fact that some of the engine power has to go to powering supercharger gears
most turbos have fuel injection systems which are more efficient than carbys, which are fitted on superchargers

56
Q

What is ground boosting

A

Turbochargers are capable of providing inlet manifold pressures above sea level pressure on the ground

57
Q

What is altitude boosting

A

Turbochargers are capable of maintaining power up to the critical altitude

58
Q

What is the critical altitude in regards to turbochargers

A

The altitude where manifold pressure can no longer be maintained

59
Q

What does the bypass duct in a turbocharger do

A

controls TURBINE rpm

60
Q

What does the wastegate doe

A

Prevents overboosting

61
Q

Describe the effects of leaks before and after the wastegate

A

before the wastegate=power loss

After the wastegate=no loss

62
Q

What does the Absolute Pressure Controller do?

A

Monitors upper deck pressure and changes the position of the wastegate to maintain this pressure

63
Q

What is bootstrapping

A

When the system tries to balance pressure even though is can’t due to the fact that the critical altitude has been reached

64
Q

Describe the positions in a wastegate on climb and descent

A

climb=close (increase UDP)

descent=opens (decrease UDP)

65
Q

How does a fuel tank stop the fuel from sloshing about

A

By implementing baffles

66
Q

Why is the top of the fuel tank vented

A

to maintain atmospheric pressure

67
Q

Why should the fuel pump be turned on when changing tanks in a carby fitted aircraft

A

To maintain fuel pressure

68
Q

Why is it normal to have the electrical fuel pump on in some stages of flight

A

because critical stages (such as a go around) require the fuel provided by the electric fuel pump if the mechanical pump fails.

69
Q

What is a rich mixture cut?

A

Engine failure do to excessively rich mixture

70
Q

Why is lead added to fuel?

A

To resist detonation

71
Q

Is MOGAS octane rated the same as AVGAS?

A

nope

72
Q

What is hydraulics

A

Force transmitted by fluid pressure

73
Q

Why do we prefer hydraulic systems over mechanical systems

A

Good power to weight ratio

74
Q

Why are fluids so good for the transmission of force

A

Fluids are considered incompressible and therefore any force applied is transferred to the next contact object

75
Q

Can you mix hydraulic fluids?

A

No

76
Q

What are the types of pumps in hydraulic systems

A 
Gear types (classic 2 gear system)
Piston type (hand pump, usually used in emergency)
Variable displacement (swashplate changes angle in order to move pistons)
77
Q

What does the accumulator in a hydraulic system do?

A

Maintains pressure in the system and dampers pressure surges

78
Q

What does a check valve do

A

Allow the travel of fluid in one direction only

79
Q

Where is the Pressure relief valve located in a hydraulic system

A

Between the pump and the system components

80
Q

What is the purpose of the Thermal Relief Valve

A

Allows fluid that has experienced thermal expansion to escape, which prevents lines from rupturing

81
Q

What does an actuator do?

A

Converts force produced by fluid pressure into movement

82
Q

What does the Emergency Extension Valve do?

A

Relieves system pressure and causes the landing gear to fall down automatically

83
Q

How does a squat switch work

A

Detects weight (checks that ac is on the ground) and prevents the gear being retracted

84
Q

How does an airswitch work

A

Prevents the undercarriage from being retracted below a certain airspeed

85
Q

Above what speeds does hydroplaning occur?

A

9X </PSI for locked wheels

86
Q

How does a thermocouple work?

A

Measures difference in temperatures from a ‘hot junction’ and ‘cold junction’

87
Q

How does a continued loop detector work?

A

Consist of an inner and outer core separated by a dialetric compound capable of detecting any overheating in the wire.

88
Q

How does a Fenwal Resistance type fire detector work?

A

Nickel wire core in a flexible inconel tube. Space between the m is a eutectic salt (has a low melting point). As the salt melts The circuit experiences a current increase, thus activating the alarm. The system is reset when the salt solidifies.

89
Q

Why is a Graviner Firewire Capacitive detector preferred over Fenwal Resistance types?

A

Because they measure both resistance and capacitance (rather than just resistance) and so the chances of a false alarm are reduced.

90
Q

How does a Systron Donner detector work?

A

Contains helium gas that expands with heat, exerting pressure on a pressure switch, which operates an alarm.

91
Q

How do carbon monoxide detectors work?

A

Contains a yellow silica gel that turns yellow when exposed to carbon monoxide. The darker the green, the more severe the exposure.

92
Q

How do photoelectric cell smoke detectors work?

A

When light can’t be transmitted onto a diode (due to smoke), tAn alert is produced

93
Q

What type of fire extinguishing system is used on most light aircraft/ smaller twin engine commercial aircraft

A

CO2/conventional type

94
Q

What type of fire extinguishing system is used on most modern commercial aircraft

A

High-Rate Discharge

95
Q

What area do extinguishers typically discharge into

A

Nacelle area (engine housing)

96
Q

What are the types of agents used in fire extinguishers

A

Methyl Bromide (MB)
Bromochlorodifloromethane (BCF)
Bromotrifloromethane (BTM)

97
Q

Why do extinguishers need to be operated in an enclosed area?

A

Because they take oxygen from the air, and so need to have a finite amount of oxygen present.

98
Q

Can BCF agents be used in fire extinguishers?

A

Although they are banned due to environemntal damage, they are exempt on aircraft due to their capability at extinguishing electrical fires

99
Q

What is the danger associated with operating an extinguisher in an enclosed area

A

asphyxiation

100
Q

Define rigidity

A

tendency for a gyroscope to maintain alignment in space

101
Q

Rigidity is proportional to….

A

Inertia X angular velocity

102
Q

What is precession

A

Tendency for a force applied to a gyroscope to be displaced 90 degrees in the direction of motion

103
Q

What is topple in regards to gyroscopes

A

Movement in the vertical plane

104
Q

Why are venturi systems used for powering gyroscopes undeesired

A

Becuase they require forward motion of the aircraft, and can only get the gyroscopes operating properly a few minutes after takeoff. They may also be affected by icing

105
Q

What disadvantages do suction gyros have to electric gyros

A

Can be affected by contaminants in the air
Can’t be operated until the engine starts
At high altitudes insufficient suction may occur
Electric gyros have a constant power and are therefore more accurate

106
Q

Why does the HI need to be realigned in flight every 15 minutes

A

because it does not seek a magnetic datum like the compass

107
Q

What is the deviation in HI readings/hour

A

10 degrees for old aircraft

1 degree for new aircraft

108
Q

What does a lattitude nut do?

A

Provides a torque proportional to the rotation of the earth and therefore prevents apparent drift in certain instruments

109
Q

What is transport error?

A

Errors in gyroscopic instrument readings due to the aircraft flying east or west (with or against the rotation of the earth), and the instrument can’t compensate for this

110
Q

The attitude indicator operates off what gyroscopic property

A

rigidity. Gyroscope stays aligned and the aircraft moves around it

111
Q

What is the typical gimbal pitch limitation

A

85 degrees

112
Q

how long can it take an erection system to level a gyro if it topples?

A

15 minutes

113
Q

What do pendulous vanes in an erection system do?

A

Makes sure the the AI gyro stays level by sensing gravity and precessing the axis

114
Q

What is a typical acceleration error on the AI

A

pitch up and to the right

115
Q

How does a turn indicator work

A

AC yaws in one direction, gimbal is precessed in the other

116
Q

The turn coordinator is sensitive to what that the turn indicator isn’t

A

roll

117
Q

What is semimonocoque

A

Frame and skin takes stress

118
Q

What is monocoque

A

Only skin takes stress

Aviation (12 decks)

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