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Cat B- Mod 11 Aircraft Systems > 11.5.6 Avionics- Fundamentals of Comms > Flashcards

11.5.6 Avionics- Fundamentals of Comms Flashcards

1
Q

What is radio telephony?

A

Sophisticated radio data communication evolved from morse code.

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2
Q

What is HF?

A

High frequency and sat com- long range

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3
Q

What is VHF?

A

Very high frequency- short range (line of sight) comms

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4
Q

What is Data Comm, ACARS, ARINC Communication and Reporting System?

A

Data in/out

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5
Q

What is ADS-B?

A

Automatic dependant surveillance broadcast- data and telemetry

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6
Q

What electromagnetic energy has the longest wavelength?

A

Radio

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7
Q

What electromagnetic energy has the shortest wavelength?

A

Gamma rays

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8
Q

What is 1 cycle per second in Hz?

A

1

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9
Q

How many cycles a second is 1MHz?

A

1 Million

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10
Q

What is a TEM wave?

A

Transverse Electromagnetic wave

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11
Q

What is a Transverse Electromagnetic wave?

A

When the oscillations are perpendicular to the direction of the waves propagation

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12
Q

Which way are radio waves polarised?

A

In the electric field (E)

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13
Q

What does a radio transmitter use a oscillator for?

A

Create the carrier wave for the station

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14
Q

What are sky waves?

A

Radio waves that travel from transmitter to receiver via the ionosphere

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15
Q

What are ground waves?

A

Radio waves that travel through the troposphere from transmitter to receiver

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16
Q

What two classifications of ground waves are there?

A

Surface
Space

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17
Q

What is a surface wave?

A

Travel along the contour of the Earth by diffraction.

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18
Q

What is a space wave?

A

Travel through the air directly to the receiving antenna in ‘line of sight’ or can be reflected from the surface of the Earth or other obstructions.

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19
Q

What three factors must be considered in the transmission of a surface wave to reduce attenuation?

A

Electrical properties of different surface types
Polarity
Frequency

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20
Q

What is the best and worst surfaces for conductivity on earth?

A

Worst- Jungle
Best- Sea water

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21
Q

How is the amount of induced voltage reduced therefore reducing the attenuation?

A

Polarised waves
Lower frequency= longer wavelength

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22
Q

What four layers does the Ionosphere have?

A

D,E,F1 and F2

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23
Q

What is the range of the D layer?

A

30 to 55 miles

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24
Q

What happens to the d layer after sunset?

A

It disappears due to rapid recombination.

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25
Q

What happens to radio waves in the ionosphere?

A

They speed up so tend to bend back towards earth.

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26
Q

What is critical frequency?

A

Maximum frequency that will refract just enough to return to Earth

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27
Q

What is the skip distance?

A

Skip distance is the distance from the transmitter to the point where the sky wave first returns to Earth

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28
Q

What is the skip zone?

A

Zone of silence between the farthest extent of ground wave transmission and the point where the sky wave first returns to Earth

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29
Q

What does the d layer reflect?

A

VLF waves

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30
Q

What does the e layer reflect?

A

HF

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31
Q

What is a CME and what is it caused by?

A

Coronal Mass Ejection- caused by geomagnetic storms.

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32
Q

What is an antenna?

A

A transducer, converts electrical power into electromagnetic waves

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33
Q

What is the simplest and most common antenna?

A

Dipole

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34
Q

What is modulation?

A

Process of encoding information from a message source in a way that is suitable for transmission

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35
Q

What are the two categories of modulation?

A

Continuous and pulse

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36
Q

What is amplitude modulation?

A

amplitude of high frequency carrier wave is varied.

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37
Q

What is angle modulation?

A

Angle of carrier wave is varied

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38
Q

What can angle modulation be further divided into?

A

Frequency and phase modulation

39
Q

What is pulse modulation?

A

Periodic sequence of rectangular pulses, is used as a carrier wave

40
Q

What is pulse modulation divided into?

A

Analog and digital

41
Q

What is PAM?

A

Pulse Amplitude Modulation

42
Q

What is PWM?

A

Pulse Width Modulation

43
Q

What is PPM?

A

Pulse Position Modulation

44
Q

What is PCM and what does it come under?

A

Pulse Code Modulation and it comes under digital modulation.

45
Q

What are some of the applications of PAM?

A

Ethernet
Micro controllers
Electronic driver for LED circuits

46
Q

What is the duty cycle?

A

Percentage of time for which the signal remains “ON”

47
Q

In modern systems, like Satcom or Mode-S Transponder what modulation is used?

A

PSk

48
Q

What is PSK?

A

Phase shift keying

49
Q

What four attributes must the receiver have?

A

Selectivity
Sensitivity
Fidelity
Stability

50
Q

What is fidelity?

A

The ability to reproduce the original modulation without distortion.

51
Q

What does the superhet do?

A

Avoids issues with sync and oscillation

52
Q

What two categories of interference are there?

A

Natural and man made

53
Q

How does a balanced circuit reduce interference?

A

Preventing inductive and capacitive coupling path interference.

54
Q

For bonding what must the resistance not exceed?

A

0.05 ohms

55
Q

What is the difference between conducted and radiated interference?

A

Conducted is direct through cables connected to equipment, radiated is through small sources of energy picked up by aerials.

56
Q

What are the service interphone sockets isolated by?

A

Weight off wheels switches

57
Q

What is priority one for the PA system?

A

Announcement from the flight deck

58
Q

What is priority two from the PA system?

A

Announcement from pax cabin

59
Q

What is priority three from the PA system?

A

Pre recorded messages

60
Q

What is priority four from the PA system?

A

Boarding music

61
Q

What is the VHF system?

A

The aircrafts principal air to air and air to ground voice and data communication system.

62
Q

What is the frequency range of the VHF system?

A

118 MHz to 136.975 MHz

63
Q

What is the formula for VHF range?

A

1.23 √hr+ht given in NM
hr- Height in feet above sea level
ht- transmitter height

64
Q

If an aircraft is at 10,000 feet and the ground station is at sea level then what is the range of the VHF?

A

123 miles

65
Q

How can the range of VHF be increased?

A

ACARS

66
Q

What frequency is weather information?

A

VOLMET 128.6
126.6 UK

67
Q

How many VHF com radios are there normally?

A

3

68
Q

How is the VHF powered in large aircraft?

A

28Vdc

69
Q

What is VHF transmitter power normally?

A

30 watts

70
Q

What does HF communication allow?

A

Long range, multi hop, worldwide, air to ground voice comms

71
Q

What is the ATU?

A

Aerial tuning unit- prevents power loss and possible damage to the transceiver.

72
Q

What types of HF aerial are there?

A

Rod
Notch
Wire

73
Q

Typically how many HF systems are there?

A

Two

74
Q

What is Inmarsat?

A

International maritime satellite, London based organisation providing satellites and ground support.

75
Q

How many Inmarsat satellites are there?

A

4 series 3
3 series 4

76
Q

What are the three levels of service of inmarsat?

A

Classic (split into 6)
Swift 64
Swift broadband

77
Q

What frequency is inmarsat?

A

1530 MHz to 1559 MHz

78
Q

What is the satcom data rate?

A

9.6 kilobits per second

79
Q

What is the ACARS system for europe?

A

SITA- 131.725 MHz

80
Q

What is the ACARS system for usa?

A

ARINC

81
Q

What times does the ACARS send a message for ETA?

A

120 mins
20 mins
7 mins

82
Q

What law requires an FDR on aircraft?

A

CS259.1459

83
Q

What level of g can the FDR’s withstand?

A

3400g

84
Q

What temp can the FDR’s withstand?

A

Over 1000 degrees c

85
Q

What is a ULB?

A

Underwater locater beacon

86
Q

How does a ULB work?

A

When it comes into contact with water, lasting for 90 days

87
Q

What is RIPS?

A

Recorder Independent Power Supply

88
Q

How long does RIPS last?

A

10 mins

89
Q

What is the ELT?

A

Emergency Locator Transmitter

90
Q

How often does ELT transmit?

A

Every 50 seconds

91
Q

What types of ELT are there?

A

Fixed- Mounted in the upper aft fuse
Portable- Crew Deployable
Fixed/portable

92
Q

Where does the ELT transmitter receive data from?

A

Aircraft and Mission Management Computer (AMMC)

93
Q

How can you ensure that the ELT is properly installed?

A

It has an arrow for direction of flight.

Cat B- Mod 11 Aircraft Systems (28 decks)

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