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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
What happens to radio waves in the ionosphere?
They speed up so tend to bend back towards earth.
26
What is critical frequency?
Maximum frequency that will refract just enough to return to Earth
27
What is the skip distance?
Skip distance is the distance from the transmitter to the point where the sky wave first returns to Earth
28
What is the skip zone?
Zone of silence between the farthest extent of ground wave transmission and the point where the sky wave first returns to Earth
29
What does the d layer reflect?
VLF waves
30
What does the e layer reflect?
HF
31
What is a CME and what is it caused by?
Coronal Mass Ejection- caused by geomagnetic storms.
32
What is an antenna?
A transducer, converts electrical power into electromagnetic waves
33
What is the simplest and most common antenna?
Dipole
34
What is modulation?
Process of encoding information from a message source in a way that is suitable for transmission
35
What are the two categories of modulation?
Continuous and pulse
36
What is amplitude modulation?
amplitude of high frequency carrier wave is varied.
37
What is angle modulation?
Angle of carrier wave is varied
38
What can angle modulation be further divided into?
Frequency and phase modulation
39
What is pulse modulation?
Periodic sequence of rectangular pulses, is used as a carrier wave
40
What is pulse modulation divided into?
Analog and digital
41
What is PAM?
Pulse Amplitude Modulation
42
What is PWM?
Pulse Width Modulation
43
What is PPM?
Pulse Position Modulation
44
What is PCM and what does it come under?
Pulse Code Modulation and it comes under digital modulation.
45
What are some of the applications of PAM?
Ethernet Micro controllers Electronic driver for LED circuits
46
What is the duty cycle?
Percentage of time for which the signal remains “ON”
47
In modern systems, like Satcom or Mode-S Transponder what modulation is used?
PSk
48
What is PSK?
Phase shift keying
49
What four attributes must the receiver have?
Selectivity Sensitivity Fidelity Stability
50
What is fidelity?
The ability to reproduce the original modulation without distortion.
51
What does the superhet do?
Avoids issues with sync and oscillation
52
What two categories of interference are there?
Natural and man made
53
How does a balanced circuit reduce interference?
Preventing inductive and capacitive coupling path interference.
54
For bonding what must the resistance not exceed?
0.05 ohms
55
What is the difference between conducted and radiated interference?
Conducted is direct through cables connected to equipment, radiated is through small sources of energy picked up by aerials.
56
What are the service interphone sockets isolated by?
Weight off wheels switches
57
What is priority one for the PA system?
Announcement from the flight deck
58
What is priority two from the PA system?
Announcement from pax cabin
59
What is priority three from the PA system?
Pre recorded messages
60
What is priority four from the PA system?
Boarding music
61
What is the VHF system?
The aircrafts principal air to air and air to ground voice and data communication system.
62
What is the frequency range of the VHF system?
118 MHz to 136.975 MHz
63
What is the formula for VHF range?
1.23 √hr+ht given in NM hr- Height in feet above sea level ht- transmitter height
64
If an aircraft is at 10,000 feet and the ground station is at sea level then what is the range of the VHF?
123 miles
65
How can the range of VHF be increased?
ACARS
66
What frequency is weather information?
VOLMET 128.6 126.6 UK
67
How many VHF com radios are there normally?
3
68
How is the VHF powered in large aircraft?
28Vdc
69
What is VHF transmitter power normally?
30 watts
70
What does HF communication allow?
Long range, multi hop, worldwide, air to ground voice comms
71
What is the ATU?
Aerial tuning unit- prevents power loss and possible damage to the transceiver.
72
What types of HF aerial are there?
Rod Notch Wire
73
Typically how many HF systems are there?
Two
74
What is Inmarsat?
International maritime satellite, London based organisation providing satellites and ground support.
75
How many Inmarsat satellites are there?
4 series 3 3 series 4
76
What are the three levels of service of inmarsat?
Classic (split into 6) Swift 64 Swift broadband
77
What frequency is inmarsat?
1530 MHz to 1559 MHz
78
What is the satcom data rate?
9.6 kilobits per second
79
What is the ACARS system for europe?
SITA- 131.725 MHz
80
What is the ACARS system for usa?
ARINC
81
What times does the ACARS send a message for ETA?
120 mins 20 mins 7 mins
82
What law requires an FDR on aircraft?
CS259.1459
83
What level of g can the FDR's withstand?
3400g
84
What temp can the FDR's withstand?
Over 1000 degrees c
85
What is a ULB?
Underwater locater beacon
86
How does a ULB work?
When it comes into contact with water, lasting for 90 days
87
What is RIPS?
Recorder Independent Power Supply
88
How long does RIPS last?
10 mins
89
What is the ELT?
Emergency Locator Transmitter
90
How often does ELT transmit?
Every 50 seconds
91
What types of ELT are there?
Fixed- Mounted in the upper aft fuse Portable- Crew Deployable Fixed/portable
92
Where does the ELT transmitter receive data from?
Aircraft and Mission Management Computer (AMMC)
93
How can you ensure that the ELT is properly installed?
It has an arrow for direction of flight.

Cat B- Mod 11 Aircraft Systems (28 decks)

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