DGCA Air Navigation: Mls Questions
53 exam-style Mls questions for the DGCA Air Navigation paper (CPL · ATPL · PPL). The first 12 are free below with answers and explanations — sign up free to practise all of them with progress tracking.
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Q1
The azimuth transmitter of a Microwave Landing System (MLS) provides a fan shaped horizontal approach zone which is usually:
- A + or - 40° of the runway centre-line
- B + or - 50° of the runway centre-line
- C + or - 60° of the runway centre-line
- D + or - 30° of the runway centre-line
Show answer
Correct answer: A. + or - 40° of the runway centre-line
An MLS azimuth transmitter sweeps a fan-shaped sector of plus or minus 40 degrees about the runway centreline, giving far wider coverage than an ILS localizer.
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Q2
Which one of the following is an advantage of a Microwave Landing System (MLS) compared with an Instrument Landing System (ILS)?
- A It is insensitive to geographical site and can be installed at sites where it is not possible to use an ILS
- B It does not require a separate azimuth (localiser) and elevation (azimuth) transmitter
- C The installation does not require to have a separate method (marker beacons or DME) to determine range
- D There is no restriction on the number of ground installations that can be operated because there is an unlimited number of frequency channels available
Show answer
Correct answer: A. It is insensitive to geographical site and can be installed at sites where it is not possible to use an ILS
A major MLS advantage is that it is far less sensitive to the surrounding terrain and reflections than ILS, so it can be sited where an ILS could not provide a usable beam.
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Q3
MLS installations notified for operation, unless otherwise stated, provide azimuth coverage of:
- A + or - 40° about the nominal courseline out to a range of 20 NM
- B + or - 20° about the nominal courseline out to a range of 20 NM
- C + or - 40° about the nominal courseline out to a range of 30 NM
- D + or - 20° about the nominal courseline out to a range of 10 NM
Show answer
Correct answer: A. + or - 40° about the nominal courseline out to a range of 20 NM
Unless otherwise notified, an MLS provides azimuth coverage of plus or minus 40 degrees about the nominal courseline out to a range of 20 NM.
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Q4
In which frequency band does the Microwave Landing System (MLS) operate?
- A SHF
- B EHF
- C VHF
- D UHF
Show answer
Correct answer: A. SHF
MLS operates in the SHF band, around 5 GHz, which allows its narrow scanning beams and wide coverage.
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Q5
Which one of the following methods is used by a Microwave Landing System (MLS) to indicate distance from the runway threshold?
- A A DME co-located with the MLS transmitters
- B Timing the interval between the transmission and reception of primary radar pulses from the aircraft to MLS station
- C Measurement of the frequency shift between the MLS azimuth and elevation transmissions
- D Timing the interval between the reception of sequential secondary radar pulses from the MLS station to the aircraft
Show answer
Correct answer: A. A DME co-located with the MLS transmitters
MLS provides range by means of a precision DME co-located with the azimuth and elevation transmitters, giving continuous distance to the threshold.
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Q6
Which one of the following correctly lists the major ground based components of a Microwave Landing System (MLS)?
- A Separate azimuth and elevation transmitters, DME facility
- B Separate azimuth and elevation transmitters, outer and middle marker beacons
- C Combined azimuth and elevation transmitter, DME facility
- D Combined azimuth and elevation transmitter, outer and inner marker beacons
Show answer
Correct answer: A. Separate azimuth and elevation transmitters, DME facility
MLS uses separate ground transmitters for azimuth and for elevation guidance, together with a co-located precision DME to provide continuous range, allowing curved and segmented approach paths.
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Q7
The coverage of MLS is …… either side of the centreline to a distance of
- A 40°, 40 nm
- B 40° 20 nm
- C 20°, 20 nm
- D 20°, 40 nm
Show answer
Correct answer: B. 40° 20 nm
This Explanation is Coming Soon
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Q8
Distance on MLS is measured by:
- A measuring the time taken for the primary radar pulse to travel from the MLS transmitter to the aircraft receiver
- B measuring the time taken for the secondary radar pulse to travel from the MLS transmitter to the aircraft receiver
- C phase comparison between the azimuth and elevation beams
- D co-located DME
Show answer
Correct answer: D. co-located DME
This Explanation is Coming Soon
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Q9
Which of the following is an advantage of MLS?
- A can be used in inhospitable terrain
- B uses the same aircraft equipment as ILS
- C has a selective access ability
- D is not affected by heavy precipitation
Show answer
Correct answer: A. can be used in inhospitable terrain
This Explanation is Coming Soon
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Q10
The frequency band of MLS is:
- A UHF
- B VHF
- C SHF
- D VLF
Show answer
Correct answer: C. SHF
This Explanation is Coming Soon
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Q11
The azimuth transmitter of a Microwave Landing System (MLS) provides a fan shaped horizontal approach zone which is usually:
- A + or - 40° of the runway centre-line
- B + or - 50° of the runway centre-line
- C + or - 60° of the runway centre-line
- D + or - 30° of the runway centre-line
Show answer
Correct answer: A. + or - 40° of the runway centre-line
The MLS azimuth transmitter radiates a fan-shaped horizontal sector normally covering plus or minus 40 degrees either side of the runway centreline. This wide proportional coverage is one of its advantages over the fixed ILS localiser.
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Q12
Which one of the following is an advantage of a Microwave Landing System (MLS) compared with an Instrument Landing System (ILS)?
- A It is insensitive to geographical site and can be installed at sites where it is not possible to use an ILS
- B It does not require a separate azimuth (localiser) and elevation (azimuth) transmitter
- C The installation does not require to have a separate method (marker beacons or DME) to determine range
- D There is no restriction on the number of ground installations that can be operated because there is an unlimited number of frequency channels available
Show answer
Correct answer: A. It is insensitive to geographical site and can be installed at sites where it is not possible to use an ILS
A major MLS advantage is that it is far less sensitive to the surrounding terrain and reflections, so it can be sited at locations where an ILS could not give a usable beam. This siting flexibility is a key improvement over ILS.
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