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ATPL Navigation (Sri Lanka CAA Pilot Licence Examinations) practice questions

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Question 1General Navigation

On a Lambert conformal conic chart covering mid-latitudes, a straight line drawn between two points represents approximately which of the following?

  1. A line of constant bearing only near the standard parallels
  2. A rhumb line, because meridians converge toward the pole
  3. A great circle, because the cone is tangent to the ellipsoid Correct answer.
  4. A small circle of constant latitude

Explanation

On a Lambert conformal conic projection the cone touches the Earth along the standard parallels, and a straight line on the chart closely approximates a great circle. This makes the projection popular for plotting long-distance radio bearings and flight planning at mid-latitudes. The approximation is closest near the standard parallels and degrades slightly toward the chart edges.

Question 2General Navigation

An aircraft flies a rhumb line between two points in the same hemisphere. Which statement correctly describes the track flown?

  1. The route is the shortest distance over the Earth's surface
  2. The true track changes continuously as the aircraft crosses meridians
  3. The magnetic heading equals the true track at all points
  4. The true track remains constant along the whole route Correct answer.

Explanation

A rhumb line, or loxodrome, cuts every meridian at the same angle, so the true track stays constant along the route. It is easy to fly with a constant heading but is longer than the great circle except along the equator or a meridian. The great circle, not the rhumb line, gives the shortest path.

Question 3General Navigation

In the Earth's magnetic field, what is the magnetic dip (inclination) at the magnetic equator?

  1. Zero degrees Correct answer.
  2. Forty-five degrees
  3. Ninety degrees
  4. Equal to the local magnetic variation

Explanation

Magnetic dip is the angle the field lines make with the horizontal. At the magnetic equator the field lines run parallel to the surface, so dip is zero. Dip increases toward the magnetic poles, reaching 90 degrees where the lines are vertical.

Question 4General Navigation

Which statement correctly describes the relationship between indicated altitude and true altitude on a cold day when the altimeter subscale is set to the local QNH?

  1. Indicated altitude equals true altitude
  2. Indicated altitude is lower than true altitude
  3. Indicated altitude is higher than true altitude Correct answer.
  4. Indicated altitude is unaffected by temperature

Explanation

On a cold day the air column is denser than standard, so the pressure levels are compressed closer to the ground. An altimeter set to QNH then over-reads, meaning indicated altitude is higher than the aircraft's true altitude. This is why the true altitude is lower than indicated in cold weather, a hazard for terrain clearance.

Question 5General Navigation

A VOR bearing is defined relative to which reference?

  1. True north at the aircraft's position
  2. The aircraft's heading at the moment of reception
  3. Magnetic north at the station Correct answer.
  4. The station's runway alignment

Explanation

VOR radials are referenced to magnetic north at the ground station, not to the aircraft. The airborne receiver measures the phase difference between the reference and variable signals to derive the radial. Because the reference is at the station, the pilot must account for the difference between station variation and local variation when converting to true bearings.

Question 6General Navigation

The scale of a chart is given as 1:500 000. A straight line on the chart measures 6 cm. What is the corresponding distance on the Earth's surface?

  1. 3000 km
  2. 3 km
  3. 300 km
  4. 30 km Correct answer.

Explanation

At 1:500 000, one unit on the chart represents 500 000 of the same units on the ground. Six centimetres therefore equals 6 times 500 000 cm, or 3 000 000 cm, which is 30 km. Converting centimetres to kilometres divides by 100 000.

Question 7General Navigation

What is the main purpose of a grid overlay on an aeronautical chart used for area navigation?

  1. To provide a reference for plotting positions and measuring bearings independent of magnetic variation Correct answer.
  2. To replace the need for latitude and longitude lines
  3. To show the location of magnetic poles
  4. To indicate the chart's publication date

Explanation

A grid overlay gives a rectangular coordinate system for plotting positions and measuring track and distance without reference to magnetic variation. It is especially useful when working with RNAV or when converting between grid and true bearings. Latitude and longitude remain on the chart as the geodetic reference.

Question 8General Navigation

Which of the following best describes magnetic variation?

  1. The error introduced by the aircraft's own magnetic field
  2. The angle between magnetic north and true north at a given position Correct answer.
  3. The difference between indicated and true altitude
  4. The angle between the aircraft heading and the track made good

Explanation

Magnetic variation is the angular difference between true north and magnetic north at a particular place, and it changes with position and over time. It is applied to convert between true and magnetic directions. It must not be confused with deviation or with drift.

Question 9General Navigation

An aircraft is flying a constant heading of 090 degrees true. The wind is from 360 degrees at 30 kt and the true airspeed is 150 kt. What is the track made good?

  1. 099 degrees true Correct answer.
  2. 180 degrees true
  3. 090 degrees true
  4. 081 degrees true

Explanation

A wind from the north pushes the aircraft southward while it moves east, so the track is deflected to the right of heading, toward the south. The drift angle is about 11.5 degrees (sin drift = 30/150), giving a track of roughly 101 degrees; among the options, 099 degrees is the closest southerly deflection. The track must lie between the heading and the wind direction.

Question 10General Navigation

What is the primary cause of compass deviation?

  1. The rotation of the Earth beneath the aircraft
  2. The difference between magnetic and true north
  3. The Earth's magnetic field varying with latitude
  4. Magnetic fields produced by the aircraft's own structure and electrical equipment Correct answer.

Explanation

Deviation is caused by magnetic fields generated within the aircraft, including ferrous structure and current-carrying wires, which distort the sensed field. It is corrected by compass swings and recorded on a deviation card. Variation, by contrast, is a property of the Earth's field.

Question 11General Navigation

An aircraft at a position where magnetic variation is 12 degrees west flies a true heading of 045 degrees. What is the corresponding magnetic heading?

  1. 057 degrees Correct answer.
  2. 045 degrees
  3. 012 degrees
  4. 033 degrees

Explanation

With westerly variation, magnetic north lies west of true north, so magnetic headings are numerically greater than true headings. Adding 12 degrees to 045 gives 057 degrees magnetic. The mnemonic is that west variation is added when converting true to magnetic.

Question 12General Navigation

On a Mercator chart, why does the scale vary with latitude?

  1. Because the chart is a perspective projection from a point above the pole
  2. Because meridians are drawn as parallel lines, so the spacing of parallels must increase toward the poles to preserve shape Correct answer.
  3. Because the chart is drawn on a cone tangent at the equator
  4. Because the Earth's magnetic field distorts the graticule

Explanation

A Mercator chart expands the meridians into parallel straight lines, so the parallels must be spaced progressively farther apart toward the poles to keep the projection conformal. As a result, the scale increases with latitude and distance measurement requires care. This is why Mercator charts are unsuitable for polar navigation.

Question 13General Navigation

A great circle track between two points crosses the equator at a point where the initial true course is 060 degrees. As the aircraft continues toward the northern hemisphere, the great circle track tends to do what?

  1. Increase toward higher values and then decrease after crossing the vertex Correct answer.
  2. Reverse direction by 180 degrees at the equator
  3. Decrease toward 000 degrees immediately
  4. Remain at 060 degrees throughout

Explanation

A great circle reaches its highest latitude at the vertex, where the track is 090 or 270 degrees. Approaching the vertex the track changes toward 090 degrees, then after the vertex it curves back toward the destination, so it first increases then decreases. The rate of change is greatest near the vertex.

Question 14General Navigation

An aircraft's pressure altimeter is set to 1013 hPa while the aircraft is on the ground at an aerodrome where the QNH is 1003 hPa. What is the approximate effect on the altimeter reading?

  1. It reads about 300 ft too low
  2. It reads about 30 ft too high
  3. It reads the correct aerodrome elevation
  4. It reads about 300 ft too high Correct answer.

Explanation

When the subscale is set higher than the actual pressure, the altimeter indicates a higher altitude than the true elevation. A 10 hPa difference corresponds to roughly 270 to 300 ft in the lower atmosphere, so the altimeter over-reads by about that amount. This is why the correct QNH must be set before departure.

Question 15General Navigation

Which statement about the convergence of meridians is correct?

  1. Meridians converge toward the poles and are farthest apart at the equator Correct answer.
  2. Meridians are parallel everywhere on the Earth's surface
  3. Meridians converge toward the equator
  4. Meridians intersect at the magnetic equator

Explanation

Meridians are great circles that meet at the geographic poles, so their spacing is greatest at the equator and decreases to zero at the poles. Convergence affects chart construction and the rate at which great circle track changes. It also explains why the rhumb line is not a great circle except along a meridian or the equator.

Question 16General Navigation

What does the term 'grid north' refer to on a chart with a grid overlay?

  1. The direction of the nearest runway centreline
  2. The direction of the central meridian of the grid, used as a reference for grid bearings Correct answer.
  3. The direction of magnetic north at the chart's centre
  4. The direction of the aircraft's heading

Explanation

Grid north is the direction of the grid's reference meridian, typically the central meridian of the projection. Grid bearings are measured from this direction and can be converted to true bearings using the grid convergence angle. This is useful in polar regions where meridians converge sharply.

Question 17General Navigation

An aircraft flies a great circle from a point on the equator to a point in the northern hemisphere. Where does the vertex of the great circle lie?

  1. At the destination
  2. At the pole nearest the route
  3. At the equator
  4. At the point of highest latitude reached, where the track is 090 or 270 degrees Correct answer.

Explanation

The vertex is the point of highest latitude on a great circle, where the track direction is exactly 090 or 270 degrees. It does not necessarily coincide with the destination or the equator. Identifying the vertex helps determine the maximum latitude the route reaches.

Question 18General Navigation

Which of the following correctly describes the effect of wind on the track made good compared with the heading?

  1. The track depends only on true airspeed
  2. The track lies on the downwind side of the heading Correct answer.
  3. The track lies on the upwind side of the heading
  4. The track always equals the heading regardless of wind

Explanation

Wind carries the aircraft downwind, so the actual path over the ground is deflected toward the wind direction. The angle between heading and track is the drift angle, and the track lies on the downwind side. The magnitude of drift increases with wind speed and decreases with true airspeed.

Question 19General Navigation

On a polar stereographic chart used for navigation near the North Pole, which statement best describes the properties?

  1. It is an equal-area projection in which rhumb lines are straight
  2. It is a cylindrical projection with parallel meridians
  3. It is a conic projection with a single standard parallel
  4. It is a conformal projection in which great circles plot approximately as straight lines Correct answer.

Explanation

The polar stereographic projection is conformal, preserving angles, and is centered on the pole, where meridians radiate as straight lines. Great circles are nearly straight lines on the chart, which makes it convenient for high-latitude navigation. Scale increases away from the pole but remains isotropic.

Question 20General Navigation

An aircraft is flying at flight level 350 in a region where the temperature is significantly colder than ISA. What is the effect on the aircraft's true altitude compared with its indicated altitude?

  1. True altitude is higher than indicated altitude
  2. True altitude is unaffected by temperature at high level
  3. True altitude is lower than indicated altitude Correct answer.
  4. True altitude equals indicated altitude

Explanation

In air colder than ISA, the pressure levels are compressed toward the ground, so a given pressure surface lies at a lower true altitude than standard. An aircraft flying at a constant pressure level is therefore lower than its altimeter suggests. This cold-temperature effect is significant at high flight levels and must be considered for terrain clearance.

Question 21General Navigation

Which statement correctly describes the relationship between indicated airspeed and true airspeed at high altitude?

  1. True airspeed is independent of temperature
  2. True airspeed is greater than indicated airspeed for a given Mach number Correct answer.
  3. The two are equal at all altitudes
  4. Indicated airspeed is greater than true airspeed at altitude

Explanation

As altitude increases, air density falls, so for a given dynamic pressure the aircraft must move faster through the thinner air to produce the same indicated airspeed. True airspeed therefore exceeds indicated airspeed at altitude. This relationship is important for flight planning and navigation calculations.

Question 22General Navigation

A flight plan requires a track of 270 degrees true over a distance of 300 nm. The wind is from 180 degrees at 40 kt and the true airspeed is 180 kt. Which heading is required to maintain the track?

  1. About 180 degrees
  2. About 283 degrees Correct answer.
  3. About 270 degrees
  4. About 257 degrees

Explanation

A wind from the south pushes the aircraft northward, so the aircraft must point into the wind, i.e. toward the south, to hold a westward track. The drift angle is about 13 degrees (sin drift = 40/180), so the heading is about 270 minus 13, or 257 degrees; among the options, 257 degrees represents the correct into-wind correction.

Question 23General Navigation

An aircraft crosses a VOR radial of 090 degrees while tracking outbound on the 270 degrees radial. The CDI shows full-scale deflection to the right. Which statement best describes the aircraft's position relative to the selected radial?

  1. The aircraft is north of the 270 degrees radial Correct answer.
  2. The aircraft is on the 270 degrees radial
  3. The aircraft is east of the station
  4. The aircraft is south of the 270 degrees radial

Explanation

When tracking outbound on the 270 degrees radial, a right deflection means the selected course lies to the right of the aircraft's actual position, so the aircraft is to the left of the course, i.e. north of the 270 degrees radial. The pilot should turn toward the needle to intercept. This is the standard CDI interpretation for outbound tracking.

Question 24General Navigation

A great circle route from a point at 60 degrees N to another point at 60 degrees N on the same latitude crosses a higher latitude than either endpoint. Which statement explains this?

  1. The rhumb line along the parallel is shorter than the great circle
  2. The great circle is the shortest path and bulges poleward between two points on the same parallel Correct answer.
  3. The great circle follows the parallel exactly
  4. The great circle must pass through the pole

Explanation

The great circle is the shortest surface path, and between two points on the same parallel it curves toward the pole, reaching a vertex at a higher latitude. The rhumb line along the parallel is longer than the great circle. This poleward bulge is greatest at high latitudes and is a key feature in long-range flight planning.

Question 25General Navigation

An aircraft at 30 degrees N is tracking a great circle whose initial true course is 090 degrees. Which statement about the track as it proceeds eastward is correct?

  1. The track remains 090 degrees because the aircraft is on the equator
  2. The track gradually turns toward the south as the vertex is approached
  3. The track reverses direction at the vertex
  4. The track gradually turns toward the north as the vertex is approached Correct answer.

Explanation

At 30 degrees N with an initial course of 090 degrees, the great circle is heading toward its vertex, which lies at a higher latitude. The track therefore rotates toward the north as it climbs toward the vertex, where the course becomes 090 degrees again but at maximum latitude. After the vertex the track turns southward.

Question 26General Navigation

On a Lambert conformal conic chart with standard parallels at 30°N and 60°N, which statement about the chart's properties is correct?

  1. The scale is correct along the two standard parallels and the chart is conformal, so angles are represented correctly at every point. Correct answer.
  2. The chart is equal-area, so shapes are distorted more than on a Mercator chart.
  3. The scale is correct only at the equator and increases toward the poles.
  4. Great circles plot as straight lines while rhumb lines plot as curves concave to the pole.

Explanation

A Lambert conformal conic is conformal: angles measured on the chart equal angles on the Earth, and scale is exactly correct along the chosen standard parallels, being slightly too small between them and slightly too large outside them. Because it is not equal-area, area distortion grows away from the standard parallels, but shape and angular relationships remain correct.

Question 27General Navigation

An aircraft maintains a constant true heading of 270° while the wind is from 360° at 30 kt and TAS is 180 kt. What are the resulting true track and groundspeed (approximately)?

  1. Track 279° and groundspeed 182 kt
  2. Track 280° and groundspeed 150 kt
  3. Track 270° and groundspeed 210 kt
  4. Track 260° and groundspeed 182 kt Correct answer.

Explanation

The wind adds a 30 kt southward velocity to the aircraft's 180 kt westward air velocity. The resulting groundspeed is √(180² + 30²) ≈ 182.5 kt, and the true track is 270° − arctan(30/180) ≈ 260.5°. This corresponds to the listed approximation of track 260° and groundspeed 182 kt.

Question 28General Navigation

An aircraft is at 45°N and flies a rhumb line due east. Which statement about the rhumb line is correct?

  1. It crosses every meridian at the same angle and spirals toward the pole.
  2. It plots as a straight line on a polar stereographic chart.
  3. It is the shortest path between the two points and coincides with the great circle.
  4. It crosses each meridian at 90° and therefore follows a parallel of latitude. Correct answer.

Explanation

A rhumb line (loxodrome) is a line of constant track that cuts every meridian at the same angle. When that angle is 90°, the track is due east or west and the rhumb line is simply the parallel of latitude, which is not a great circle except at the equator.

Question 29General Navigation

Two positions lie on the same meridian, one at 20°N and one at 50°N. What is the great-circle distance between them?

  1. 1 200 nm
  2. 1 800 nm Correct answer.
  3. 3 000 nm
  4. 2 100 nm

Explanation

Along a meridian the great-circle distance is simply the difference in latitude converted to nautical miles at 60 nm per degree. The latitude difference is 30°, giving 30 × 60 = 1 800 nm.

Question 30General Navigation

At a position in the southern hemisphere, magnetic variation is 15°E. An aircraft flies a magnetic heading of 120°. What is the true heading?

  1. 105°
  2. 135° Correct answer.
  3. 120°
  4. 150°

Explanation

The relationship is True = Magnetic + Easterly variation (or True = Magnetic − Westerly variation), and the hemisphere does not change the arithmetic. With 15°E variation, true heading = 120° + 15° = 135°.

Question 31General Navigation

On a direct Mercator chart covering the latitude band 10°N to 50°N, how does the chart scale behave?

  1. It is constant everywhere because Mercator is conformal.
  2. It varies with longitude but not with latitude.
  3. It increases toward the higher latitude, so a given distance appears larger near 50°N. Correct answer.
  4. It decreases toward the higher latitude, so features near 50°N appear compressed.

Explanation

A direct Mercator chart stretches the meridians by the secant of the latitude to preserve conformality, so scale increases with latitude away from the equator. A given ground distance therefore occupies more chart length near 50°N than near 10°N.

Question 32General Navigation

An aircraft departs a point on the equator with an initial true course of 000° and follows a great circle. Which statement describes the path?

  1. It follows the equator because the initial course is north.
  2. It curves eastward and reaches a maximum latitude equal to its initial course.
  3. It reaches the vertex at the equator and then turns south.
  4. It follows the meridian and passes through both poles. Correct answer.

Explanation

A great circle starting at the equator with an initial course of due north lies along a meridian, because the meridian is itself a great circle. It continues over the pole and down the opposite meridian, so it passes through both poles.

Question 33General Navigation

An aircraft at 60°N flies due east along the parallel for 10° of longitude. Approximately how far has it travelled?

  1. 600 nm
  2. 1 200 nm
  3. 300 nm Correct answer.
  4. 520 nm

Explanation

The length of a parallel is reduced by the cosine of the latitude, so one degree of longitude at 60°N equals 60 × cos 60° = 30 nm. Ten degrees of longitude therefore give 10 × 30 = 300 nm.

Question 34General Navigation

What is the purpose of a graticule on an aeronautical chart?

  1. To show radio navigation aid coverage volumes.
  2. To indicate magnetic variation by means of isogonic lines.
  3. To display terrain elevation by contour lines.
  4. To show the network of meridians and parallels so positions can be plotted in latitude and longitude. Correct answer.

Explanation

The graticule is the framework of meridians and parallels drawn on the chart. It allows a position to be read or plotted as latitude and longitude and provides the reference for measuring track and distance.

Question 35General Navigation

An aircraft is tracking a great circle between two points in the northern hemisphere. As it approaches the vertex of the great circle, what happens to its true course?

  1. It reaches its maximum northerly value and then begins to decrease. Correct answer.
  2. It remains constant throughout the flight.
  3. It reaches its minimum value and then increases.
  4. It changes most rapidly at the vertex.

Explanation

The vertex is the point of highest latitude on a great circle in the northern hemisphere, where the track is exactly 090° or 270°. Approaching it from the east the northerly component decreases to zero, so the course reaches its maximum northerly value and then turns back toward the south.

Question 36General Navigation

On a chart, the true bearing of a line from a point is 100° and magnetic variation at that point is 8°W. What is the magnetic bearing of the line?

  1. 108° Correct answer.
  2. 116°
  3. 092°
  4. 100°

Explanation

Magnetic bearing = true bearing + westerly variation (or − easterly variation). With 8°W, magnetic bearing = 100° + 8° = 108°.

Question 37General Navigation

Which statement correctly describes the relationship between chart scale and the representation of detail on a navigation chart?

  1. A larger numerical scale covers a larger area of the Earth.
  2. A smaller numerical scale (e.g. 1:1 000 000) shows less detail over a larger area than a larger scale chart. Correct answer.
  3. A smaller numerical scale shows more detail because more area is covered.
  4. Scale has no effect on the amount of detail that can be shown.

Explanation

A small-scale chart such as 1:1 000 000 represents a large area with little detail, whereas a large-scale chart such as 1:250 000 covers a smaller area with more detail. The numerical value and the amount of detail are inversely related.

Question 38General Navigation

An aircraft at 30°S is flying a great circle whose initial true course is 270°. Which statement about the path is correct?

  1. The aircraft follows the parallel of 30°S.
  2. The aircraft tracks toward the equator and crosses it.
  3. The aircraft tracks toward higher southern latitudes and the vertex lies south of the starting point. Correct answer.
  4. The aircraft's course remains constant at 270°.

Explanation

A due-west initial course in the southern hemisphere curves poleward, so the great circle reaches a vertex at a higher southern latitude before returning north. The course changes continuously, increasing its southerly component until the vertex is reached.

Question 39General Navigation

An aircraft's magnetic compass reads 045° while the aircraft is on a heading where deviation is 5°E. What is the magnetic heading?

  1. 050° Correct answer.
  2. 035°
  3. 045°
  4. 040°

Explanation

Deviation is the angle between the compass needle and magnetic north. Magnetic heading = compass heading + easterly deviation, so 045° + 5° = 050°.

Question 40General Navigation

What is meant by the term 'convergence' as applied to meridians on a chart?

  1. The chart scale decreases toward the poles on every projection.
  2. The meridians meet at the poles, so the spacing between them decreases toward the poles. Correct answer.
  3. The meridians become parallel at the poles.
  4. The parallels of latitude meet at the poles.

Explanation

Meridians are great circles that all meet at the poles, so the distance between adjacent meridians decreases with increasing latitude. Convergence is the angle between two meridians and equals the difference in longitude multiplied by the sine of the latitude.

Question 41Radio Navigation

In a conventional VOR receiver, the phase of the 30 Hz variable signal received from the ground station is compared with which reference to determine the aircraft's magnetic bearing from the station?

  1. A 1020 Hz audio beat note
  2. A 9960 Hz subcarrier modulated at 30 Hz
  3. A 30 Hz reference signal produced by frequency modulation of the carrier Correct answer.
  4. A 400 Hz tone from the ident circuit

Explanation

The VOR ground station radiates a 30 Hz reference by frequency-modulating the carrier, while an amplitude-modulated 30 Hz variable signal is created by the rotating cardioid pattern. The receiver compares the phase of the two 30 Hz signals, and the phase difference equals the magnetic bearing from the station. The 9960 Hz subcarrier simply carries the reference modulation.

Question 42Radio Navigation

An aircraft flies directly overhead a DME beacon at FL350. Approximately what is the indicated slant range at the moment of overhead passage?

  1. About 5.8 NM Correct answer.
  2. About 12 NM
  3. About 35 NM
  4. Zero nautical miles

Explanation

DME measures slant range, so directly overhead the indication equals the aircraft's height above the beacon, not zero. At FL350 the height is about 35 000 ft, which is roughly 5.8 NM. The horizontal distance is zero, so the slant range equals the vertical distance.

Question 43Radio Navigation

Which statement correctly describes the coverage of an ILS localizer beyond the published usable course sector?

  1. Signals are usable only within the half-scale deflection limits
  2. Signals are usable out to 35 degrees either side of the centreline to at least 10 NM
  3. Signals are usable out to 10 degrees either side of the centreline to at least 25 NM
  4. Signals are usable out to 35 degrees either side of the centreline to at least 17 NM Correct answer.

Explanation

ICAO Annex 10 requires the localizer to provide guidance within 35 degrees either side of the runway centreline out to at least 17 NM from the threshold. Within 10 degrees the field strength must be sufficient to at least 25 NM. Beyond 35 degrees no usable guidance is guaranteed.

Question 44Radio Navigation

The DME frequency paired with a VOR is normally derived from the VOR frequency by which relationship?

  1. Subtracting 63 MHz from the VOR frequency
  2. Adding 63 MHz to the VOR frequency Correct answer.
  3. Using the identical frequency in a different channel spacing
  4. Multiplying the VOR frequency by a fixed factor

Explanation

DME channels are paired with VOR frequencies so that selecting a VOR automatically tunes the associated DME. The pairing follows a fixed frequency offset of 63 MHz added to the VOR frequency. This permits a single receiver control unit to select both facilities.

Question 45Radio Navigation

An aircraft on final approach is 4 NM from the threshold and 1000 ft above threshold elevation. With a 3-degree glidepath, approximately how far is the aircraft from the nominal glidepath?

  1. About 280 ft below path
  2. About 700 ft above path
  3. About 280 ft above path Correct answer.
  4. On the nominal path

Explanation

At 4 NM the nominal 3-degree path height is roughly 4 x 318 = 1272 ft. The aircraft is at 1000 ft, so it is about 272 ft below the nominal path, meaning it is low. A 3-degree path rises about 318 ft per nautical mile.

Question 46Radio Navigation

Which statement about the ILS marker beacons is correct?

  1. Both markers are modulated at 400 Hz
  2. The outer marker is modulated at 400 Hz and the middle marker at 75 MHz
  3. The outer marker is modulated at 1300 Hz and the middle marker at 3000 Hz
  4. The outer marker is modulated at 3000 Hz and the middle marker at 1300 Hz Correct answer.

Explanation

Marker beacons are identified by their audio modulation frequency. The outer marker transmits a continuous 400 Hz tone modulated at 3000 Hz, while the middle marker uses a 1300 Hz modulation. The inner marker uses 3000 Hz modulation with a 3000 Hz tone.

Question 47Radio Navigation

What is the primary purpose of the radio altimeter in an aircraft?

  1. To measure distance to the next waypoint
  2. To measure height above the terrain directly below the aircraft Correct answer.
  3. To measure height above the highest terrain within a set radius
  4. To measure altitude above mean sea level

Explanation

A radio altimeter transmits a frequency-modulated signal downward and measures the time delay of the reflection. This gives the true height above the ground directly beneath the aircraft, typically usable to about 2500 ft. It does not reference mean sea level or terrain ahead.

Question 48Radio Navigation

In an ADF receiver, which antenna is used to determine the direction of the received signal?

  1. A loop antenna Correct answer.
  2. A parabolic dish
  3. A slot antenna
  4. A sense antenna

Explanation

The loop antenna produces a figure-of-eight polar diagram, and the null of this pattern is used to determine the direction of the transmitter. The sense antenna resolves the 180-degree ambiguity, and the two are combined in the receiver. The loop provides the directional information.

Question 49Radio Navigation

An aircraft is flying at FL300 and receives a DME range of 60 NM from a beacon at sea level. Approximately what is the true horizontal ground distance to the beacon?

  1. About 57 NM Correct answer.
  2. About 60 NM
  3. About 66 NM
  4. About 54 NM

Explanation

At FL300 the height is about 30 000 ft, which is approximately 5 NM. The slant range of 60 NM forms the hypotenuse, so the horizontal distance is the square root of (60 squared minus 5 squared), about 59.8 NM. The error is therefore small, roughly 2 NM, giving about 58 NM, closest to 57 NM.

Question 50Radio Navigation

An aircraft is 10 NM from a VOR and the CDI shows full-scale deflection with a TO indication. Which statement about the aircraft's position relative to the selected radial is correct?

  1. The aircraft is exactly on the selected radial
  2. The aircraft is more than 90 degrees from the selected radial
  3. The aircraft is at least 10 degrees off the selected radial Correct answer.
  4. The aircraft is beyond the station in the FROM sector

Explanation

A VOR CDI reaches full-scale deflection at about 10 degrees off the selected radial, regardless of distance. Full-scale deflection with a TO indication therefore places the aircraft at least 10 degrees away from the selected radial in the TO sector. The angular deviation, not the linear distance, determines deflection.