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Part 2 > 123 Systems > Flashcards

123 Systems Flashcards

1
Q

Surface waves follow the earths curvature due to:

A

Diffraction and Scattering

(Caused by objects redirecting radio waves downward

Influences LF waves more)

Wave tilting

(Wave contacts earth and slows down, tilting down and increasing attenuation)

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2
Q

Frequency range of surface/ground waves:

A

VLF, LF, MF

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3
Q

Advantages of surface waves:

A

Long ranges of transmission possible

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4
Q

Disadvantages of surface waves:

A

Low-efficiency aerials (long) required
Higher static levels
Higher power demand
Higher instalation cost

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5
Q

Sky waves are caused by:

A

Refraction of waves in the ionosphere

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6
Q

What happens to different frequencies of sky waves upon reaching the ionosphere?

A

LF - trapped/absorbed
>HF - penetrate and continue to space

MF/HF bands most suited

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7
Q

What is the critical angle (sky waves)?

A

The smallest angle to the vertical which is capable of producing a return wave from the ionosphere

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8
Q

What is the skip distance?

A

Earth distance between the transmitter and first returning sky wave

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9
Q

What influences the skip distance?

A

Diurnal changes of the ionosphere. Rises during night and increases skip distance.

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10
Q

What is dead space?

A

Distance between end of surface waves and the following sky wave

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11
Q

What are direct waves?

A

Line of sight radio waves - VHF and higher

(travel in straight lines and do not bend around obstacles)

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12
Q

Theoretical range formula

A

Range (Nm) = 1.25sqr TX alt + 1.25sqr RX alt

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13
Q

What is the purpose of a VOR

A

To transmit signals used for short range navigation

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14
Q

Bearing from a VOR is measured by

A

Phase comparison (reference and variable phase signal)

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15
Q

DVOR reference signal is _____ modulated at ____ Hz

A

Amplitude, 30

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16
Q

DVOR variable signal is _____ modulated at ____ Hz

A

Frequency, 30

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17
Q

The inner marker beacon is ________ threshold and ______ modulated at ____ Hz

A

runway, amplitude, 3,000 (white)

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18
Q

The outer marker beacon is ________ from threshold and ______ modulated at ____ Hz

A

3-6Nm, amplitude, 400 (blue)

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19
Q

The middle marker beacon is ________ from threshold and ______ modulated at ____ Hz

A

0.6Nm, amplitude, 1,300 (amber)

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20
Q

What is the coverage and range of LOC

A

+/- 35Ā° to 17Nm
+/- 10Ā° to 25Nm

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21
Q

What is the coverage and range of GS

A

+/- 8Ā° to 10Nm

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22
Q

What frequencies are the upper/lower of GS

A

150Hz lower
90Hz upper

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23
Q

What frequencies are L/R of LOC

A

90hz left (yellow)
150Hz right (blue)

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24
Q

What is the freq range of LOC

A

108-112 MHz
VHF (odd No after decimal)

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25
Q

What frequency band is glideslope

A

UHF (300MHz)

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26
Q

What is the frequency range of VOR

A

112-117.95 MHz

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27
Q

What is the frq of glideslope carrier wave

A

75MHz

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28
Q

3 methods of magnetisation

A

Induction
Electro-magnetism
Repetitive stroking

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29
Q

Methods of demagnetisation

A

De-gausing
Percussion
Heating
Induction

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30
Q

What is flux density

A

lines per of magnetic flux per unit area

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31
Q

Inverse cube law

A

The strength of the magnetic field about a magnet is inversely proportional to the cube of the distance from the pole of the magnet in relation to its strength at the pole

(distance from the pole increases - strength of field decreases at a rate of power of 3)

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32
Q

Changes to the earths magnetic field occur (daily/annually/11 yearly):

A

Daily - due to electric currents flowing in ionosphere

Annually - due to sun varying distance from earth

11 years - sunspot activity

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33
Q

Hard iron has ____ retentitvity, ____ permeability

A

high, low

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34
Q

Soft iron has ____ retentivity, ____ permeability

A

low, high

35
Q

Component P is _____ axis

A

Longitudinal

36
Q

Component Q is _____ axis

A

Lateral

37
Q

Component R is _____ axis

A

Normal

38
Q

Methods to reduce a/c magnetism

A

De-gaussing after manufacture

Moving a/c while not in use

Calibration (with systems running to allow for temporary magnetism)

Compass swinging

39
Q

Compass swinging is usually required every ___ months.

A

24

40
Q

What freq band does DME use?

A

UHF (960-1215 mHz)

41
Q

What is the range of DME?

A

200Nm at 30,000ft (with a 50 microsecond delay)

42
Q

How many pulse pairs can DME ground equip respond to a second?

A

2700

43
Q

How many a/c can use DME at a time?

A

126, in practice, 100

44
Q

DME provides the ____ ______ between the a/c and the ground station

A

Slant range

45
Q

for DME the interrogating station is _____ and the transponder is ______

A

the aircraft, the ground station

46
Q

for DME the aircraft sends out paired pulses with a ______ PRF

A

random

47
Q

DME ground station responds to the a/c with _______ pulse pairs on a frequency ___ _____ or ______ delayed by _______

A

the same, 63mHz higher or lower, 50 microseconds

48
Q

What is the design and actual accuracy of DME?

A

Design +/- 0.5Nm (3%)
Actual +/- 0.2Nm (0.25%)

49
Q

DME operates using _____ _____ _____?

A

Secondary Surveillance Radar (SSR)

50
Q

AWR operates on the _____ band or __ band, typically _____

A

SHF, X, 9.4 GHz

51
Q

AWR range by ____ principle

A

Echo (Primary Radar)

52
Q

AWR bearing by _____ principle

A

Searchlight

53
Q

AWR antenna has a _____ guide and a _____ antenna

A

Wave, slotted

54
Q

AWR tilt control optimizes ______ of significant ______

A

detection, weather

55
Q

AWR beam width should be keep as _____ as possible

A

Narrow

56
Q

Stab control purpose:

A

to keep the antenna parallel to the ground while the a/c is in pitch or roll

57
Q

Gain control purpose:

A

shows relative intensity between cells

58
Q

Limitations of AWR

A

Requires high degree of operator skill
DRY ice absorbs and does not reflect radar

59
Q

Components of an ELT (3)

A

VHF transmitter
Antenna
Remote switch

60
Q

Where are ELT located?

A

Aft of a/c

61
Q

How do ELT operate?

A

ā€œGā€ operated, Tx transmits interrupted carrier wave with no modulation. Satellite receives carrier wave and calculates ELT position (45 mins). Info sent to ground station and forwarded to SAR.

Distress signal on separate frequency used to determine precise location

62
Q

How many types of VHF/UHF ELT are there?

A

2 (other calculates GPS location and fwd to SAR)

63
Q

ELT requirements

A

Able to survive crash
Able to be removed from a/c
Able to be pacified
Able to activate from cockpit
Meet FAA TSO c126 (design)

64
Q

ELT serviceability requirements

A

100-hour check
G switch as part of 24 month

65
Q

RIC accuracy

A

+/- 0.5 degree (3 deg required without gyro, 2 deg with)

66
Q

RIC ____ magnetic field, DRC _____ with magnetic field

A

senses, aligns

67
Q

Limitations of RIC

A

Limited use near the poles
Synchronization limited to 2deg/min

68
Q

RIC errors

A

Transmission error (wires/insulation)
Coriolis error

69
Q

Deviation in the RIC is corrected with:

A

Coefficient A:
Compass swing

Coefficient B/C:
Potentiometer (adjustable variable resistor) connected to pick-up coils

70
Q

Radar freq band

A

UHF/SHF

71
Q

Radar pulse technique principle

A

Transmission of a pulsed signal, detects target through an echo. Pulsing allows for ranging, echo is timed (d=s/t) /2.

72
Q

Pulse width

A

Length of time a pulse is transmitted

73
Q

Pulse recurrence frequency (PRF)

A

Length of time between pulses

74
Q

The strength of radar echo depends on:

A

Range of target
Power of transmitter
Shape/surface of the target
Size of the object in relation to the size of WL

75
Q

Primary radar uses ____ technique. Antenna rotates ______ and focused by a _________ which enables ______ between targets and improves _______ of bearings

A

Pulse, between 2-10 rpm (12deg/sec), narrow beam, discrimination, accuracy

76
Q

Minimum range of radar

A

1Nm (aprx)

77
Q

Limitations of Primary Radar

A

No alt information
Difficult to identify/track specific a/c

78
Q

Function of MTI

A

Returning frequencies are compared and only those with a phase change are shown on display (doppler effect)

79
Q

XPDR principle

A

Ground based interogater transmits pulse pairs to trigger a/c (0.85 microsec) at 1030Hz, a/c transmits 2 pulses at 1090Mhz (20.3 microsec) with 12 pulses within the 2 frame pulses. 1x pulse left out relating to xpdr code and 1x pulse added if alt info required.

80
Q

Possible xpdr codes

A

2^12 = 4096

Codes from 0000-7777 (no 8 or 9)

Every 100ft up to 126,000ft =
16,700,000 mode S codes

81
Q

Max xpdr range

A

256Nm (complies with line of sight formula)

82
Q

Power requirements of SSR vs PR

A

requirements for SSR are half that of PR

83
Q

AWR sweeps ____ degrees either side of the nose and ____ degrees up/down

A

60, 15

84
Q
A

Part 2 (7 decks)

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