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Module 13 EASA Part 2 > Part 4 - Navigation Systems > Flashcards

Part 4 - Navigation Systems Flashcards

1
Q

What will an ADF indicate when correctly tuned to a ground station?

A

Either the relative or the magnetic bearing of that station depending on the type of display fitted on the flight deck

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2
Q

What is an RBI?

A

Relative bearing indicator

Stationary rose with 0° indicating the nose of the aircraft and the needle pointing to the relative bearing of the ADF station

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3
Q

What is an RMI?

A

Radio magnetic indicator

Rotating compass rose controlled by the aircraft gyrocompass, simultaneous reading of relative and magnetic bearing of the transmitter, and also the aircraft heading

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4
Q

What frequency range does the ADF ground station (beacon) cover?

A

190 kHz to 2 MHz

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5
Q

What is the nature of the signal transmitted by the ground ADF beacon and what is it known as?

A

Omnidirectional

Non-directional beacon (NDB)

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6
Q

What frequencies do commercial broadcast stations transmit on, and what is the disadvantage of these stations with regards to ADF?

A

550 kHz to 1.6 MHz

They identify themselves only about once every half hour

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7
Q

What is the polarisation of the ADF signal?

A

Vertically polarised

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8
Q

When radiated from a vertical aerial, what might the transmissions from an NDB be?

A

Either carrier wave (CW) keyed for identification in morse code

or

Keyed modulated carrier wave (MCW) modulated at 1020 Hz

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9
Q

Why is the power output of an NDB deliberately limited?

A

To obtain only the range of operation that is required

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10
Q

What is the Bellini-Tosi system?

A

The fixed loop system to which most modern ADF systems work

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11
Q

What is the purpose of the omnidirectional sense antenna in an ADF system?

A

Acts as a reference, without it there would be two nulls on the loop antenna, one a reciprocal of the other, so the sense antenna resolves the ambiguity

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12
Q

Which component of electromagnetism does the sense aerial respond to?

A

E component

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13
Q

How will the voltages produced by sense aerials below the aircraft differ from those above?

A

180° out of phase

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14
Q

Why is there ARINC specification requirements regarding sense capacity and what is it?

A

The sense aerial circuit is required to present a specified total capacitance to the ADF receiver input

3000 pf

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15
Q

What must be used in ARINC installations where a sense cable less than 60 ft is used?

A

By using sense aerial matching unit, sense aerial cable equaliser or susceptiformer

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16
Q

Where is the sense aerial matching normally installed and why?

A

At the receiver end of the sense aerial cable

To increase the apparent total capacitance of the sense aerial plus the sense cable to the required value

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17
Q

Where must the loop aerial be mounted?

A

On the fuselage with its longitudinal centre line on the aircraft longitudinal centre line, aligned mechanically within 1.25°

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18
Q

Where is the ideal position of the sense aerial?

A

At the electrical centre of the aircraft

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19
Q

What are the three types of loop error in ADF?

A
  • Quadrantal error
  • Loop alignment error
  • Field alignment error
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20
Q

Which procedure can be carried out to determine the nature and size of any errors in an ADF system?

A

Loop swing

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21
Q

What should be ensured about the state of the aircraft before carrying out a loop swing?

A

Must contain its full complement of equipment

Doors and panels in the vicinity of the ADF aerials must be closed and secured

Internal power supplies should be used whenever possible

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22
Q

What is Night Effect?

A

Inaccurate, broad and varying nulls caused by polarisation changes of the vertically polarised signals

Effect is magnified at sunrise and sunset because activity in the ionosphere is most pronounced during these periods

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23
Q

What is vertical or antenna effect?

A

If the vertical limbs of a loop aerial are not balanced to earth, it is possible that the voltages induced in the vertical limbs produce an effective loop voltage which is not a minimum at the true null points

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24
Q

What are the types of VOR?

A

Conventional VOR

Doppler VOR

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25
Q

What frequencies does VOR operate on?

A

108 MHz to 118 MHz

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26
Q

What great advantage does VOR have over ADF?

A

It does not suffer the night effect

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27
Q

What is the range of VOR?

A

Line of sight

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28
Q

What is the principle of operation of VOR?

A

Phase comparison

The aircraft’s equipment derives from the phase difference between two 30 Hz modulations associated with the radio frequency transmission of the ground beacon

29
Q

What is the difference between the transmitted signals of a VOR system?

A

Reference signal - omni-directional and frequency modulated at 30 Hz

Variable signal - directional and amplitude modulated at 30 Hz

30
Q

What reading does the RMI give?

A

Direct reading of the beacon bearing relative to magnetic north

31
Q

Describe the TO/FROM circuit in the navigation unit?

A

Senses the cosine output from the Omni-Bearing Selector (OBS) and causes the appropriate flag to be displayed on the OBS

32
Q

Describe a category A VOR beacon?

A
  • Used for normal en route navigation
  • Carrier RF power output of about 200W
  • Service range of up to about 200nm
33
Q

Describe a category B VOR beacon?

A
  • Used to provide approach and let down information to an aircraft
  • Power output of about 50W
  • Limited coverage range of about 25nm
34
Q

What are the signal phase angle relationships at each quadrature of the VOR beacon?

A

Magnetic north - reference phase and the variable phase signals are in phase
East of the beacon - signals are 90° out of phase, the variable phase lagging the reference phase signal
South of the beacon - signals are 180° out of phase, variable lagging reference
West of the beacon - signals are 270° out of phase, variable lagging reference

35
Q

What is the ‘cone of confusion’?

A

Reception of the beacon signal is reduced to a minimum at angles of elevation greater than 40°

36
Q

What is the result of the ‘cone of confusion’?

A

A VOR receiver gives a bearing indication which is characterised by violent fluctuations

37
Q

What is the general allowable error of a VOR beacon?

A

2°

38
Q

What is the major cause of error in the CVOR system?

A

Multipath error

39
Q

What is multipath error?

A

Signals which arrive at the receiver may include those which arrive after reflection from objects, both natural and man-made, located in the area of the beacon

40
Q

What is ground station error?

A

The 30 Hz reference phase and the 30 Hz variable phase to be out of alignment at the VOR station’s north bearing alignment

41
Q

What is the fundamental difference between CVOR and DVOR?

A

Reference and variable phases have changed over

In CVOR, it is the 30 Hz AM the carrier which is azimuth dependent

In DVOR, it is the 30 Hz FM the 9960 Hz subcarrier which is azimuth dependent

42
Q

Describe the elevation transmitter in MLS?

A
  • Fan shaped narrow beam in the vertical limit between 0.9° to 7.5°
  • Most in-service installations actually cover a sector up to 15° above the surface
43
Q

What is the sweep angle either side of the centreline in MLS?

A

40°

44
Q

What additional elements might be contained in expanded configuration of MLS?

A
  • Back azimuth equipment to support the missed approach procedure
  • Flare elevation equipment to support autoland functions
  • Extended azimuth coverage over 360°
45
Q

Describe the channels and frequencies of MLS?

A
  • 200 channels
  • 5031 to 5090.7 MHz
  • Each channel paired with an associated DME
46
Q

What are the advantages of MLS over ILS?

A
  • Increased traffic handling
  • Freedom from radio interference
  • Can be installed at difficult sites where ILS could not
  • Economical to maintain
  • Very wide three-dimensional coverage for curved flight paths, different glide slopes for final approaches
  • More flexibility in control of aircraft in terminal areas
47
Q

Describe the accuracy of MLS?

A

The system is fully able to support Category 3 operations with accuracy at the threshold typically plus or minus 20 feet in azimuth and 2 feet in elevation

48
Q

What is the channel spacing in MLS?

A

300 kHz

49
Q

What does GNSS stand for?

A

Global Navigation Satellite System

50
Q

How many satellites are required for an accurate 3D position?

A

4

51
Q

What error could be expected by time errors?

A

1 ns error would give an error of 30 cm

1 microsecond error would give an error of 300 m

52
Q

Describe the NAVSTAR GPS system?

A
  • 24 satellites orbiting the Earth in six orbital planes at a height of 11,000 nm
  • Four operation satellites and a spare satellite in each orbital plane
  • Orbital period of a NAVSTAR satellite is 11 hours 58 minutes
53
Q

What are the two levels of GPS service?

A
  • Standard positioning service for general civil use
  • Precise positioning service, primarily intended for use by DoD and US allies
54
Q

Describe the two L band frequencies used by GPS?

A
  • L1 carries the precision ranging code (P(Y) code) and a coarse acquisition ranging code (C/A code)
  • L2 carries only the P(Y) code
55
Q

What is mask angle?

A

Signals from satellites with low angles of elevation in relation to the horizon have a greater distance to travel through the ionosphere and troposphere, and so pseudo-range error, and multipath error are likely

The receiver excludes satellites below a fixed elevation angle relative to the horizon

56
Q

What is RAIM?

A

Receiver Autonomous Integrity Monitoring

Detection of incorrect signals from a faulty GPS satellite

Using at least 5 satellites, the software compares the time and position information derived from various combinations of four satellites

An abnormal solution will indicate the presence of a faulty satellite

Six satellites allows the aircraft to detect a fault satellite and continue integrity monitoring

57
Q

What is INS primarily concerned with?

A

Newton’s second law and the ability of the system to detect minute changes in velocity

58
Q

Describe INS?

A
  • Self contained method of navigation
  • Independent of external sources of information
  • Unaffected by bad weather, radio interference or any other condition that would render other methods of navigation impossible
59
Q

Why are rate integrating gyros the type usually used in INS?

A
  • High sensitivity
  • Ability to accurately record displacements from a given datum position
60
Q

Gimbal gain can be calculated by which formula?

A

Gimbal gain = output/input

61
Q

What is gimbal lock?

A

A condition where the two axes of rotation become co-linear and in consequence a degree of freedom is lost

62
Q

How can gimbal lock be prevented?

A

Using a four gimbal system

63
Q

What is apparent wander?

A

Wander due to the rotation of the Earth

64
Q

What are bounded errors?

A

Errors which oscillate about a mean and do not grow with time

65
Q

How do the errors which originate in the Schuler loop propagate?

A

They are oscillatory and therefore propagate at the Schuler frequency

66
Q

What type of acceleration errors occur in accelerometers?

A
  • Centripetal accelerations
  • Coriolis acceleration
67
Q

What causes coriolis acceleration errors?

A

Aircraft following a curved path in space

68
Q

What causes centripetal acceleration errors?

A

Platform being rotated to maintain the local Earth vertical

Module 13 EASA Part 2 (7 decks)

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