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EASA ATPL062 radio-navigation foundations study materials
EASA ATPL062 radio-navigation foundations study resources

EASA ATPL062 radio-navigation foundations practice questions

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Question 1Conventional aids, bearing and distance interpretation

Within which frequency band do conventional VOR and Doppler-VOR ground stations transmit?

  1. 108.000-117.975 MHz (VHF) Correct answer.
  2. 190-1750 kHz (LF/MF)
  3. 962-1213 MHz (UHF)
  4. 5031-5091 MHz (SHF)

Explanation

VOR (including DVOR) operates in the VHF band from 108.000 to 117.975 MHz, sharing the lower part (108.000-111.975 MHz) with ILS localizers, which is why ILS localizer frequencies fall on the odd-tenth/odd-hundredth pattern.

Question 2Conventional aids, bearing and distance interpretation

An NDB transmits on a frequency of 350 kHz. In which propagation band does this navaid principally operate, and what is its main associated error at dusk and dawn?

  1. VHF band; site error
  2. HF band; coastal refraction only
  3. UHF band; slant-range error
  4. LF/MF band; night effect (ionospheric/twilight error) Correct answer.

Explanation

NDBs operate in the LF/MF band (ICAO 190-1750 kHz). At dawn and dusk the changing ionosphere returns sky waves that contaminate the ground wave, producing the bearing fluctuations known as night effect (twilight error).

Question 3Conventional aids, bearing and distance interpretation

An aircraft on a magnetic heading of 075° displays an ADF relative bearing of 132° on a fixed-card (relative-bearing) indicator. What is the magnetic bearing TO the NDB (QDM)?

  1. 057°
  2. 243°
  3. 027°
  4. 207° Correct answer.

Explanation

QDM (magnetic bearing to the station) equals magnetic heading plus relative bearing: 075° + 132° = 207°. With a fixed card the pilot must add the relative bearing to heading mentally.

Question 4Conventional aids, bearing and distance interpretation

On a Radio Magnetic Indicator (RMI) the compass card is slaved to the aircraft heading. To read the QDR (magnetic bearing FROM the NDB), the pilot reads which part of the needle?

  1. The head (point) of the needle
  2. The lubber line at the top of the instrument
  3. The 90° mark to the right of the head
  4. The tail of the needle Correct answer.

Explanation

On an RMI the head of the needle indicates QDM (bearing to the station) and the tail indicates QDR (bearing from the station). Because the card is slaved to heading, both are read directly in magnetic terms.

Question 5Conventional aids, bearing and distance interpretation

A Terminal VOR (TVOR) differs from a standard en-route VOR principally because it:

  1. Transmits in the UHF band to avoid interference
  2. Uses pulse techniques instead of phase comparison
  3. Provides distance as well as bearing without a co-located DME
  4. Is a lower-power VOR with a shorter range used in the approach/departure structure of major aerodromes Correct answer.

Explanation

A TVOR is a reduced-power VOR with a deliberately short range, installed to support the approach and departure structure at busy aerodromes where a full-power en-route VOR is unnecessary.

Question 6Conventional aids, bearing and distance interpretation

A conventional VOR derives the aircraft's bearing by comparing two 30 Hz signals. Which statement correctly describes these signals?

  1. A reference phase (constant, omnidirectional) and a variable phase (whose phase depends on bearing) Correct answer.
  2. Two variable phases rotating in opposite directions at 15 Hz
  3. A pulse-pair whose spacing encodes the radial
  4. An amplitude-only signal with no phase information

Explanation

A conventional VOR transmits a 30 Hz reference phase (frequency-modulated on a 9960 Hz subcarrier, omnidirectional) and a 30 Hz variable phase (amplitude-modulated by the rotating pattern). The phase difference between them equals the magnetic radial.

Question 7Conventional aids, bearing and distance interpretation

A Doppler-VOR (DVOR) was developed mainly to overcome which limitation of the conventional VOR?

  1. Its short range over water
  2. Its lack of an identification signal
  3. Its inability to be used below 1000 ft AGL
  4. Its susceptibility to siting errors caused by reflections from terrain and buildings Correct answer.

Explanation

The DVOR's large counterpoise and electronically rotated wide-aperture antenna make it far less sensitive to multipath/siting errors from nearby terrain and obstructions, which is the main reason it replaced conventional VOR at difficult sites.

Question 8Conventional aids, bearing and distance interpretation

Full-scale deflection of a VOR CDI (five dots) corresponds to an angular displacement from the selected radial of approximately:

  1. ±2°
  2. ±5°
  3. ±10° Correct answer.
  4. ±20°

Explanation

A standard VOR CDI shows full-scale deflection at ±10° from the selected radial, so each dot represents about 2°. (ILS localizer deflection by contrast is far more sensitive, full scale at about ±2.5°.)

Question 9Conventional aids, bearing and distance interpretation

An aircraft overhead a DME station at 6000 ft (1 NM = 6076 ft) reads a DME distance of approximately:

  1. 0.0 NM
  2. It will not lock on overhead
  3. 6.0 NM
  4. 1.0 NM Correct answer.

Explanation

DME measures slant range, not ground distance. Directly overhead a station at 6076 ft, the slant range is the height itself, about 1 NM. This is why DME 'distance to run' is least accurate close in and at high altitude.

Question 10Conventional aids, bearing and distance interpretation

When a pilot tunes a VOR/DME paired frequency, the DME channel is selected automatically. This pairing means the DME actually operates in which band?

  1. VHF, the same as the VOR
  2. SHF (5 GHz)
  3. LF/MF
  4. UHF (962-1213 MHz) Correct answer.

Explanation

Although VOR and DME frequencies are paired so a single VHF selection tunes both, the DME itself transmits and receives in the UHF band (962-1213 MHz). The VHF channel selection is simply mapped to a UHF DME channel.

Question 11Conventional aids, bearing and distance interpretation

An ILS localizer transmits in which band, and its centreline is defined by the equality of which two modulation tones?

  1. UHF; 90 Hz and 150 Hz
  2. SHF; 90 Hz and 150 Hz
  3. VHF; 1300 Hz and 2100 Hz
  4. VHF (108.10-111.95 MHz); 90 Hz and 150 Hz Correct answer.

Explanation

The ILS localizer operates in the VHF band on odd-tenth frequencies between 108.10 and 111.95 MHz. On the extended runway centreline the depth of modulation of the 90 Hz and 150 Hz tones is equal (zero DDM).

Question 12Conventional aids, bearing and distance interpretation

The ILS glide path transmits in the UHF band and a standard glide path is set to which nominal angle?

  1. 2.0°
  2. 6.0°
  3. 4.5°
  4. 3.0° Correct answer.

Explanation

The ILS glide path is a UHF signal (around 329-335 MHz) normally set to a 3.0° descent angle, with the 90 Hz tone predominating above the path and the 150 Hz tone below it.

Question 13Conventional aids, bearing and distance interpretation

An aircraft intercepting the ILS from the LEFT of the localizer and from BELOW the glide path will see which indications on the cross-pointer display?

  1. Localizer needle left of centre, glide path needle below centre
  2. Both needles centred
  3. Localizer needle right of centre, glide path needle below centre
  4. Localizer needle right of centre, glide path needle above centre Correct answer.

Explanation

ILS displays are command instruments: 'fly toward the needle'. Being left of the centreline drives the localizer needle to the right (fly right), and being below the path drives the glide path needle up (fly up), so the needle appears above centre.

Question 14Conventional aids, bearing and distance interpretation

For a CAT I ILS, the protected coverage of the localizer is normally guaranteed out to:

  1. 25 NM within ±10° and 17 NM within ±35° of the centreline Correct answer.
  2. 5 NM all round
  3. 60 NM within ±10°
  4. Only along the runway centreline with no angular spread

Explanation

ICAO Annex 10 defines localizer coverage to 25 NM within ±10° and 17 NM within ±35° of the front-course centreline. The signal is guaranteed within a defined angular sector, not all-round.

Question 15Conventional aids, bearing and distance interpretation

The Microwave Landing System (MLS) provides guidance using which technique and band?

  1. Phase comparison in the VHF band
  2. Doppler shift in the UHF band
  3. Pulse ranging in the LF band
  4. Time-referenced scanning beam (TRSB) in the SHF band (5031-5091 MHz) Correct answer.

Explanation

MLS uses a time-referenced scanning beam (TRSB) in the SHF band between 5031 and 5091 MHz (200 channels). The aircraft computes azimuth and elevation from the time interval between TO and FRO beam passages.

Question 16Conventional aids, bearing and distance interpretation

A key operational advantage of MLS over ILS is that MLS:

  1. Requires no aircraft receiver
  2. Provides distance information without any DME
  3. Works without line of sight
  4. Offers a wide, selectable approach sector allowing curved and segmented approaches Correct answer.

Explanation

MLS provides proportional guidance over a wide azimuth (typically ±40°) and elevation sector, enabling curved, segmented and steep approaches that a single fixed ILS beam cannot offer. This flexibility was a primary design goal.

Question 17Conventional aids, bearing and distance interpretation

VHF Direction Finding (VDF) at an aerodrome gives the controller a bearing of the aircraft. The maximum range at which a VDF bearing can be obtained depends primarily on:

  1. The transmitter power of the NDB
  2. The number of satellites in view
  3. The ionospheric reflection at the time
  4. The heights of the aircraft and of the ground station (line of sight) Correct answer.

Explanation

VDF works on VHF and is therefore line-of-sight limited; the maximum range depends on the height of the aircraft and the height of the receiving station, following the standard VHF range formula.

Question 18Conventional aids, bearing and distance interpretation

A VDF bearing passed to a pilot as a magnetic heading to steer (in nil-wind) to reach the station is classified as a:

  1. QDM Correct answer.
  2. QDR
  3. QTE
  4. QFE

Explanation

A QDM is the magnetic heading to steer (zero wind) to reach the station; QDR is the magnetic bearing from the station, QTE is the true bearing from the station, and QFE is an altimeter pressure setting, not a bearing.

Question 19Conventional aids, bearing and distance interpretation

Coastal refraction, an NDB error, is greatest when the signal crosses the coastline at:

  1. 90° (a right angle)
  2. It is independent of crossing angle
  3. Exactly 45°
  4. A small (shallow) angle close to the coast Correct answer.

Explanation

Coastal refraction bends the NDB ground wave as it passes from land to sea (different conductivities). The error is greatest when the wave crosses the coast at a shallow angle and is least (near zero) when it crosses at right angles.

Question 20Conventional aids, bearing and distance interpretation

An aircraft tracks the 045° radial outbound from a VOR. The OBS is set to 045° and the FROM flag shows. If the CDI is deflected to the right, the aircraft is:

  1. Left of the desired radial (on a lower-numbered radial) Correct answer.
  2. Right of the desired radial (on a higher-numbered radial)
  3. Exactly on the radial
  4. Tracking toward the station

Explanation

With a FROM indication and a right CDI deflection, the desired track is to the right of the aircraft, meaning the aircraft is left of the selected radial. To regain track the pilot flies toward the needle (turns right).

Question 21Conventional aids, bearing and distance interpretation

A DME 'arc' procedure requires the pilot to maintain a constant DME distance from the station. To fly the arc accurately, the aircraft heading relative to the bearing to the station should be kept close to:

  1. Directly toward the station
  2. Approximately 90° to the bearing to/from the station Correct answer.
  3. Directly away from the station
  4. 45° to the runway centreline

Explanation

To maintain a constant range from the DME, the aircraft must fly tangentially to the arc, i.e. about 90° to the bearing to (or from) the station, making small heading adjustments as the radial changes to hold the DME distance constant.

Question 22Conventional aids, bearing and distance interpretation

Why does an ADF needle point toward a thunderstorm rather than the tuned NDB when flying near active convection?

  1. Because thunderstorms transmit on the NDB frequency deliberately
  2. Because lightning discharges radiate strong LF/MF energy that the ADF loop senses as a stronger 'station' Correct answer.
  3. Because the VOR overrides the ADF
  4. Because the ADF switches to GNSS mode automatically

Explanation

Lightning produces broadband bursts including strong LF/MF energy; the ADF, sensing the direction of the strongest signal, can swing toward the storm instead of the tuned NDB, which is a recognised limitation when operating near thunderstorms.

Question 23Conventional aids, bearing and distance interpretation

The ILS marker beacons (outer, middle, inner) transmit vertically upward on a common frequency of:

  1. 75 MHz Correct answer.
  2. 108 MHz
  3. 330 MHz
  4. 1090 MHz

Explanation

ILS marker beacons all transmit on 75 MHz, fan-shaped upward, distinguished by their tone and light: outer (400 Hz, blue, dashes), middle (1300 Hz, amber, dot-dash), inner (3000 Hz, white, dots).

Question 24Conventional aids, bearing and distance interpretation

An ILS localizer also produces a 'back course' behind the array. Why must crews use caution with the back course on a standard ILS?

  1. The back course gives accurate glide-path guidance
  2. There is no glide path on the back course, and localizer sensing may be reversed unless a back-course mode is used Correct answer.
  3. The back course is always more accurate than the front course
  4. The back course transmits on a different frequency

Explanation

The localizer back course provides only lateral guidance (no glide path), and unless the receiver has a back-course mode, the left/right sensing is reversed. Many ILS installations do not protect or authorise back-course approaches.

Question 25Conventional aids, bearing and distance interpretation

During an ILS approach, an aircraft or vehicle entering the ILS sensitive area can cause:

  1. A frequency change of the localizer
  2. Localizer/glide-path beam bends (course deviations), which is why ILS critical/sensitive areas are protected in low visibility Correct answer.
  3. An increase in glide-path angle to 6°
  4. Automatic transfer to MLS

Explanation

Reflections from large vehicles or aircraft in the ILS sensitive area can distort (bend) the localizer or glide-path signal, causing deviations. This is why these areas are protected, especially during CAT II/III operations in low visibility.

Question 26Conventional aids, bearing and distance interpretation

A VOR 'cone of confusion' is the region:

  1. Directly above the station where bearing information becomes unreliable Correct answer.
  2. At maximum range where the signal is weakest
  3. Below 1000 ft only
  4. Where two VORs overlap

Explanation

Directly overhead a VOR there is a cone-shaped zone in which the rapidly changing geometry and signal nulls make bearing indications unreliable (the TO/FROM flips and the CDI becomes erratic) until the aircraft passes the station.

Question 27Propagation, radar and surveillance

Which factor most directly limits the maximum reception range of VHF/UHF navaids such as VOR, ILS and DME?

  1. Sky-wave (ionospheric) absorption
  2. Static interference from precipitation
  3. Coastal refraction
  4. Line-of-sight propagation set by the heights of transmitter and receiver Correct answer.

Explanation

VHF and UHF navaids propagate by space (line-of-sight) wave, so the maximum range is limited by the radio horizon, which depends on the heights of the transmitter and the aircraft, approximated by 1.23 times the square root of height in feet (in NM).

Question 28Propagation, radar and surveillance

The radio horizon (maximum theoretical reception range) for a VHF transmitter at sea level and an aircraft at 10,000 ft is closest to which value, using range (NM) = 1.23 x sqrt(height in feet)?

  1. About 39 NM
  2. About 79 NM
  3. About 123 NM Correct answer.
  4. About 250 NM

Explanation

For a station effectively at the surface, range = 1.23 x sqrt(10000) = 1.23 x 100 = 123 NM. This formula gives the VHF/UHF line-of-sight radio horizon used for VOR/DME planning.

Question 29Propagation, radar and surveillance

An electromagnetic wave with a frequency of 300 MHz has a wavelength (in free space) of approximately:

  1. 1 m Correct answer.
  2. 10 m
  3. 100 m
  4. 0.1 m

Explanation

Wavelength = c / frequency = 300,000,000 m/s / 300,000,000 Hz = 1 m. This relationship (wavelength in metres = 300 / frequency in MHz) is fundamental to antenna sizing and band identification.

Question 30Propagation, radar and surveillance

Which propagation path allows long-range HF communication well beyond the line of sight, by reflection from the ionosphere?

  1. Surface (ground) wave
  2. Tropospheric ducting only
  3. Space wave
  4. Sky wave Correct answer.

Explanation

HF (3-30 MHz) achieves long ranges principally by sky-wave propagation: the wave is refracted by the ionosphere back toward the surface, allowing intercontinental coverage with appropriate frequency selection.

Question 31Propagation, radar and surveillance

A half-wave dipole antenna is cut for a frequency of 75 MHz. What is its approximate physical length?

  1. 1 m
  2. 0.5 m
  3. 4 m
  4. 2 m Correct answer.

Explanation

Wavelength = 300 / 75 = 4 m, so a half-wave dipole is approximately 2 m long. Antenna physical dimensions scale directly with wavelength, which is why LF/MF antennas are large and SHF antennas tiny.

Question 32Propagation, radar and surveillance

Doppler shift, used in DVOR and exploited in some radar systems, is the change in received frequency caused by:

  1. Atmospheric temperature changes
  2. Antenna polarisation mismatch
  3. Ionospheric absorption
  4. Relative motion between transmitter and receiver (or reflector) Correct answer.

Explanation

Doppler shift arises from relative motion: closing motion raises the received frequency and opening motion lowers it. Pulsed-Doppler weather radar uses this to derive the radial velocity of precipitation (turbulence/windshear).

Question 33Propagation, radar and surveillance

Primary surveillance radar (PSR) determines target position by:

  1. Receiving a coded reply from an aircraft transponder
  2. Decoding a GNSS position broadcast by the aircraft
  3. Comparing the phase of two ground signals
  4. Timing the echo of its own transmitted pulse reflected from the aircraft skin Correct answer.

Explanation

PSR is independent and non-cooperative: it transmits a pulse and measures range from the round-trip time of the energy reflected (skin paint) from the aircraft, and bearing from the antenna pointing direction. No airborne equipment is required.

Question 34Propagation, radar and surveillance

In secondary surveillance radar (SSR), the ground interrogator transmits on 1030 MHz and the aircraft transponder replies on:

  1. 1030 MHz
  2. 1215 MHz
  3. 978 MHz
  4. 1090 MHz Correct answer.

Explanation

SSR uses an interrogation frequency of 1030 MHz and a reply frequency of 1090 MHz. Mode S and 1090 MHz Extended Squitter ADS-B share this reply frequency.

Question 35Propagation, radar and surveillance

Which SSR mode provides automatic pressure-altitude reporting from the aircraft to the ground?

  1. Mode A
  2. Mode 1
  3. Mode S selective only
  4. Mode C Correct answer.

Explanation

Mode A provides the four-digit identity (squawk) code, while Mode C provides automatic pressure-altitude reporting in 100 ft increments. Mode S can also report altitude (in 25 ft increments) and adds selective addressing.

Question 36Propagation, radar and surveillance

Mode S improves on classic SSR primarily because it:

  1. Replies to every interrogation with the same code
  2. Requires no transponder in the aircraft
  3. Operates in the VHF band
  4. Uses a unique 24-bit aircraft address for selective interrogation, reducing garbling and supporting data link Correct answer.

Explanation

Mode S assigns each aircraft a unique 24-bit address so the ground station can interrogate selectively, which reduces garbling and over-interrogation (FRUIT) and enables ground-air data link and ADS-B.

Question 37Propagation, radar and surveillance

Airborne weather radar typically operates in the X-band (around 9 GHz). Why is this band chosen for detecting precipitation?

  1. Because X-band passes through cloud without any reflection
  2. Because it avoids reflection from the largest raindrops
  3. Because it provides long-range ground mapping only
  4. Because the short wavelength is efficiently reflected by water droplets while keeping antenna size small Correct answer.

Explanation

X-band wavelengths (about 3 cm) are well matched to raindrop size, giving strong returns from precipitation, and the short wavelength allows a compact nose antenna with a narrow beam. Larger hail/wet droplets give the strongest returns (magenta/red).

Question 38Propagation, radar and surveillance

Pulse repetition frequency (PRF) of a radar sets the maximum unambiguous range. A low PRF (long interval between pulses) generally provides:

  1. A shorter maximum range but better velocity resolution
  2. Higher bearing accuracy only
  3. A longer maximum unambiguous range Correct answer.
  4. No effect on range

Explanation

Maximum unambiguous range is set by the time between transmitted pulses; a lower PRF means a longer listening interval, so echoes from more distant targets return before the next pulse, giving a longer unambiguous range.

Question 39Propagation, radar and surveillance

Static interference (precipitation static) is most disruptive to reception on which navaid?

  1. VOR
  2. ADF/NDB (LF/MF) Correct answer.
  3. DME (UHF)
  4. ILS glide path (UHF)

Explanation

Precipitation static and atmospheric noise predominate at lower frequencies, so the LF/MF ADF/NDB is the navaid most degraded by static (e.g. in or near thunderstorms), where the ADF needle may even point at the storm rather than the beacon.

Question 40Propagation, radar and surveillance

ADS-B (Automatic Dependent Surveillance - Broadcast) on 1090 MHz Extended Squitter is best described as:

  1. A primary radar that needs no transponder
  2. A system that broadcasts the aircraft's GNSS-derived position and identity automatically, without interrogation Correct answer.
  3. A ground-based ranging aid
  4. An ILS replacement

Explanation

ADS-B is automatic and dependent: the aircraft automatically broadcasts its own GNSS-derived position, velocity and identity (no interrogation needed). Ground stations and other aircraft (ADS-B IN) receive it for surveillance and traffic awareness.

Question 41Propagation, radar and surveillance

The unwanted reception of replies triggered by interrogations from OTHER ground stations, seen on classic SSR, is known as:

  1. FRUIT Correct answer.
  2. Garbling
  3. Squitter
  4. Clutter

Explanation

FRUIT (False Replies Unsynchronised In Time, or to Interrogations Tracked) refers to replies a transponder makes to other interrogators being received by a station that did not trigger them. Mode S selective interrogation reduces FRUIT.

Question 42Propagation, radar and surveillance

On airborne weather radar, tilting the antenna UP from level flight will primarily:

  1. Reduce ground returns and show weather at higher altitudes/longer range tops Correct answer.
  2. Increase ground clutter in the near field
  3. Disable the gain control
  4. Convert the display to a map mode

Explanation

Tilting the beam up reduces near-field ground returns and lets the crew examine the tops/upper portions of cells and weather at range; tilting down increases ground returns (useful for ground mapping) and shows lower precipitation.

Question 43Propagation, radar and surveillance

The narrow horizontal beamwidth of a radar antenna mainly improves:

  1. Range resolution
  2. Bearing (azimuth) resolution and accuracy Correct answer.
  3. Maximum unambiguous range
  4. Receiver sensitivity to weak echoes

Explanation

A narrow horizontal beamwidth lets the radar distinguish targets close together in azimuth and improves bearing accuracy. Range resolution, by contrast, depends on pulse length, and maximum range on PRF.

Question 44Propagation, radar and surveillance

Which statement about polarisation of the ADF/NDB system is correct?

  1. NDBs radiate a horizontally polarised wave received by a vertical loop
  2. NDBs radiate a vertically polarised ground wave; the ADF sense antenna and loop are designed to receive it Correct answer.
  3. Polarisation is irrelevant at LF/MF
  4. NDBs use circular polarisation like GNSS

Explanation

NDBs radiate a vertically polarised ground wave at LF/MF, and the ADF system (loop plus sense antenna) is designed around this polarisation; sky-wave contamination, which can change polarisation, contributes to night effect errors.

Question 45Propagation, radar and surveillance

The propagation speed of radio waves in free space, used in all radio-ranging calculations, is approximately:

  1. 300 m/s
  2. 3 x 10^5 km/s (3 x 10^8 m/s) Correct answer.
  3. 1100 km/h
  4. 1.5 x 10^8 m/s

Explanation

Radio waves travel at the speed of light, about 3 x 10^8 m/s (300,000 km/s). This constant underlies DME ranging (round-trip timing) and GNSS pseudo-range computation.

Question 46GNSS, augmentation and PBN concepts

Area navigation (RNAV) is best defined as a method of navigation that permits aircraft operation:

  1. Only directly overhead ground navaids
  2. Solely by dead reckoning
  3. On any desired flight path within the coverage of referenced navaids, or within the limits of self-contained aids, or a combination Correct answer.
  4. Only along published airways defined by VOR radials

Explanation

ICAO defines RNAV as a method permitting operation on any desired flight path within the coverage of station-referenced navaids, or the limits of self-contained aids (e.g. INS/GNSS), or a combination, freeing the aircraft from overflying ground stations.

Question 47GNSS, augmentation and PBN concepts

A basic 2D RNAV system computes the aircraft position relative to a phantom waypoint defined by:

  1. A bearing and distance (rho-theta) from a VOR/DME station Correct answer.
  2. GNSS only, with no ground reference
  3. A barometric altitude and time
  4. Two NDB bearings

Explanation

Simple 2D RNAV creates a phantom waypoint by offsetting from a VOR/DME station using a rho-theta (distance-bearing) computation, allowing the CDI to be flown to a point that is not at the station itself.

Question 48GNSS, augmentation and PBN concepts

A modern Flight Management System (FMS) computes the most accurate position by:

  1. Using a single GNSS receiver only
  2. Averaging two VOR radials
  3. Blending (Kalman-filtering) multiple sensors such as IRS, GNSS, and DME/DME or VOR/DME Correct answer.
  4. Using barometric altitude alone

Explanation

An FMS derives an optimum (best computed) position by statistically blending inputs from several sensors, typically IRS plus GNSS and radio updating (DME/DME or VOR/DME), using a Kalman filter that weights each by its estimated accuracy.

Question 49GNSS, augmentation and PBN concepts

When an FMS updates its position using ground navaids, the most accurate radio update is normally obtained from:

  1. A single VOR bearing
  2. A single NDB
  3. DME/DME (two or more DMEs) Correct answer.
  4. VDF bearings

Explanation

DME/DME updating using two (preferably more, with good geometry) DME stations gives a precise range-range fix and is generally the most accurate ground-based radio update an FMS uses, more accurate than a single VOR/DME.

Question 50GNSS, augmentation and PBN concepts

In an FMS flight plan, a waypoint at which the aircraft must cross at or above/below a specified altitude is an example of:

  1. A fly-by waypoint
  2. A holding fix only
  3. A vertical (altitude) constraint Correct answer.
  4. A magnetic variation correction

Explanation

An altitude (vertical) constraint at a waypoint tells the FMS VNAV function the required crossing altitude window (at, at-or-above, at-or-below, or between), shaping the computed vertical profile for the procedure.