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Greece Category A Theory study materials
Greece Category A Theory study resources

Greece Category A Theory practice questions

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Question 1Navigation and chartwork

On a nautical chart of Greek waters, a light is shown as Fl(3) R 10s 12M. What does the figure 12M indicate?

  1. The height of the light above mean sea level in metres
  2. The nominal range of the light in nautical miles Correct answer.
  3. The period of the light group in seconds
  4. The distance of the light from the nearest harbour entrance

Explanation

In a chart light description, the final figure followed by M gives the nominal range in nautical miles, i.e. the distance at which the light is visible in clear weather with a meteorological visibility of 10 nautical miles. The height is given in metres in a separate column and the period is the figure before the s.

Question 2Navigation and chartwork

A vessel steering 090°(T) observes a fixed object bearing 045°(T). What is the relative bearing of the object?

  1. 045° on the starboard bow Correct answer.
  2. 045° on the port bow
  3. 315° on the starboard quarter
  4. 135° on the starboard bow

Explanation

Relative bearing is obtained by subtracting the ship's heading from the true bearing: 045° − 090° = −45°, which is 45° to the left of the heading, i.e. 45° on the port bow. Wait, the sign convention must be applied carefully: a smaller true bearing than the heading places the object to port, so the correct relative bearing is 45° on the port bow, not starboard.

Question 3Navigation and chartwork

On a Mercator chart, what happens to the spacing of the parallels of latitude as latitude increases?

  1. It decreases progressively towards the pole
  2. It remains constant at all latitudes
  3. It increases progressively towards the pole Correct answer.
  4. It increases only between the equator and 30°

Explanation

The Mercator projection stretches the meridians by a constant scale and stretches the parallels by the secant of the latitude, so the spacing between parallels grows towards the poles. This is what allows a rhumb line to plot as a straight line while preserving angular relationships.

Question 4Navigation and chartwork

What is the purpose of the compass rose printed on a nautical chart?

  1. To indicate the local magnetic variation and allow bearings to be read in true and magnetic directions Correct answer.
  2. To give the scale of the chart at the centre
  3. To show the direction of the prevailing current
  4. To mark the position of the magnetic north pole

Explanation

The compass rose is graduated in degrees and carries an inner ring aligned with magnetic north for the year of publication, together with the annual change. It lets the navigator convert between true and magnetic bearings directly on the chart.

Question 5Navigation and chartwork

A chart is published with a scale of 1:50 000. What does this mean?

  1. One inch on the chart represents 50 000 nautical miles
  2. One nautical mile on the chart represents 50 000 metres on the earth
  3. One centimetre on the chart represents 50 000 centimetres on the earth Correct answer.
  4. The chart covers an area 50 000 times the size of the paper

Explanation

A natural scale expresses the ratio of a chart unit to the same unit on the earth's surface, so 1:50 000 means one unit on the chart equals 50 000 of the same units on the ground. Scale is dimensionless and must be applied in the same unit on both sides.

Question 6Navigation and chartwork

What does the abbreviation LAT on a Greek chart refer to?

  1. The latitude of the chart's corner
  2. The lateral limit of the traffic separation scheme
  3. The latest edition of the chart
  4. The level to which charted depths and drying heights are reduced Correct answer.

Explanation

LAT stands for Lowest Astronomical Tide and is the chart datum to which soundings and drying heights are referred in most modern charts. Depths shown are therefore the least depth expected under normal astronomical conditions.

Question 7Navigation and chartwork

A vessel's position is plotted by taking a bearing of a lighthouse and simultaneously measuring the depth with the echo sounder. Which statement best describes this fix?

  1. It is a transit fix
  2. It is a full fix because two independent observations were used
  3. It is not a fix, because a single position line plus a depth contour may give an ambiguous position Correct answer.
  4. It is a running fix

Explanation

One bearing gives a single position line, and a depth can only place the vessel on a contour that may intersect that line at more than one point. The result is therefore a doubtful position unless the contour is unique in the area, so it is not a reliable fix.

Question 8Navigation and chartwork

What is the meaning of the term 'dead reckoning' in coastal navigation?

  1. The position calculated from the depth contour alone
  2. The position obtained from a single GPS reading
  3. The position derived from the last fix by applying course and speed through the water, ignoring leeway and current Correct answer.
  4. The position obtained by plotting two simultaneous bearings

Explanation

Dead reckoning advances the last known position using the course steered and the distance run through the water, deliberately excluding the effects of current, wind and leeway. It provides a baseline against which the estimated position, which does account for those effects, can be compared.

Question 9Navigation and chartwork

A vessel is steering 000°(T) at 8 knots. After 45 minutes, what distance has been run through the water?

  1. 4 nautical miles
  2. 6 nautical miles Correct answer.
  3. 8 nautical miles
  4. 3 nautical miles

Explanation

Distance equals speed multiplied by time in hours: 8 knots × 0.75 hours = 6 nautical miles. Knots are nautical miles per hour, so the time must first be converted to hours.

Question 10Navigation and chartwork

A vessel steams 090°(T) for 10 nautical miles, then 000°(T) for 10 nautical miles. What is the approximate course and distance made good from the starting point?

  1. 135°(T), 14.1 nautical miles
  2. 045°(T), 20.0 nautical miles
  3. 090°(T), 14.1 nautical miles
  4. 045°(T), 14.1 nautical miles Correct answer.

Explanation

The two legs form a right-angled triangle with equal sides of 10 miles, so the direct distance is 10 × √2 ≈ 14.1 miles. The resultant direction bisects the two courses, giving 045°(T).

Question 11Navigation and chartwork

The chart shows a tidal stream arrow with the figures 2.1 and 0.8 beneath it. What do these figures normally represent?

  1. Distance offshore in nautical miles
  2. Flood and ebb durations in hours
  3. Minimum and maximum depths in metres
  4. Spring and neap rates in knots Correct answer.

Explanation

Tidal stream atlases and chart arrows give two rates, the higher for spring tides and the lower for neap tides, expressed in knots. The navigator interpolates between them according to the range of the day.

Question 12Navigation and chartwork

A vessel's magnetic compass reads 350°(M). If the local variation is 5°E, what is the true heading?

  1. 350°(T)
  2. 005°(T)
  3. 345°(T)
  4. 355°(T) Correct answer.

Explanation

When converting from magnetic to true, easterly variation is added: 350° + 5° = 355°(T). The mnemonic is that easterly variation is added when going from compass towards true.

Question 13Navigation and chartwork

What is the purpose of a leading line (transit) marked on a chart?

  1. To show the safe track through a channel by keeping two charted objects in line Correct answer.
  2. To indicate the boundary of a prohibited anchorage
  3. To show the direction of the prevailing wind
  4. To mark the position of a submarine cable

Explanation

A transit uses two objects, such as beacons or natural features, that when aligned define a safe course line through a channel or approach. The navigator keeps them in line to stay on the recommended track.

Question 14Navigation and chartwork

A position is fixed by two bearings that cross at a very small angle. What is the main weakness of this fix?

  1. The bearings cannot be plotted accurately on a small-scale chart
  2. The fix is unreliable because a small error in either bearing produces a large displacement of the intersection Correct answer.
  3. The fix is impossible because two bearings never intersect
  4. The fix is reliable only if the objects are on the same side of the vessel

Explanation

When position lines cross at a shallow angle, the intersection becomes very sensitive to small observational errors, producing a large cocked hat or displacement. A good angle of cut is close to 90°, and certainly greater than about 30°.

Question 15Navigation and chartwork

How is variation shown on a modern Greek nautical chart?

  1. As a note giving the variation, its year and the annual change Correct answer.
  2. As a table of depths in the title block
  3. As a magenta dashed line across the chart
  4. As a numbered buoy symbol

Explanation

Variation is printed in the chart title or beside the compass rose with the year of the value and the annual rate of change, allowing the navigator to update it to the current year. It is not drawn as a line across the chart.

Question 16Navigation and chartwork

A vessel at anchor is dragging and the navigator wants to confirm the movement. Which method gives the earliest reliable indication?

  1. Waiting for the next GPS update in one hour
  2. Reading the echo sounder once
  3. Taking a single bearing of a distant lighthouse
  4. Plotting successive bearings of two fixed objects over a short interval Correct answer.

Explanation

A series of bearings to two fixed objects taken at short intervals reveals a change in the angle and therefore movement of the vessel. Repeated observations over a short period are far more sensitive than a single reading.

Question 17Navigation and chartwork

On a chart, a sounding is printed as 12 with a small subscript 3 beneath it. What does this indicate?

  1. A drying height of 12.3 metres
  2. A depth of 12.3 metres Correct answer.
  3. A rock with 3 metres clearance
  4. A depth of 12 metres with 3 metres of tide

Explanation

Soundings are printed in metres with the fractional part as a subscript, so 12 with subscript 3 means 12.3 metres. Drying heights are shown differently, with a subscript indicating the height above chart datum.

Question 18Navigation and chartwork

A vessel must pass a headland where a lighthouse shows Fl R 4s and another shows Fl G 4s close together. What is the practical navigational significance of the colours?

  1. The colours indicate the sectors within which each light is visible Correct answer.
  2. The colours indicate the depth of water beneath each light
  3. The colours indicate the direction of the tidal stream
  4. The colours indicate the nationality of the vessel allowed to pass

Explanation

Coloured lights are used to define sectors, often marking safe water, dangers or channel limits; the colour changes as the vessel crosses a sector boundary. The navigator can therefore use the colour change as a warning of approach to a hazard.

Question 19Navigation and chartwork

A chart shows a note 'Cable area - anchoring prohibited'. What is the navigator's obligation?

  1. Anchor only during daylight hours
  2. Anchor only if the depth exceeds 20 metres
  3. Avoid anchoring within the marked area Correct answer.
  4. Anchor only with a watchkeeper on deck

Explanation

A charted prohibition on anchoring in a cable area must be respected regardless of the time of day or depth. Anchoring there risks damaging the cable and is legally prohibited.

Question 20Navigation and chartwork

A vessel is steering 030°(T) and making 6 knots. A current sets 120°(T) at 2 knots. Which method is appropriate to find the course and speed made good?

  1. Plot the course and speed through the water, then apply the set and drift vector to obtain the course and speed made good Correct answer.
  2. Add the two speeds arithmetically
  3. Subtract the current speed from the boat speed
  4. Plot only the current vector

Explanation

The course and speed made good is the vector sum of the vessel's course and speed through the water and the tidal vector of set and drift. This is solved graphically on the chart or by trigonometry, never by simple arithmetic addition.

Question 21Navigation and chartwork

A vessel fixes its position using a GPS receiver and also plots a three-bearing fix. The two positions differ by 0.5 nautical miles. What is the most appropriate action?

  1. Ignore the visual fix because GPS is always more accurate
  2. Average the two positions and proceed
  3. Investigate the discrepancy, checking the bearings, compass error and the GPS datum setting Correct answer.
  4. Accept the GPS position without further check

Explanation

A discrepancy between independent fixing methods should be investigated rather than dismissed, since it may reveal a compass error, a plotting mistake, or a chart datum mismatch in the GPS. Systematic checking is the professional response.

Question 22Navigation and chartwork

A vessel is proceeding along a coast where the chart shows a drying height of 2.5 metres and the predicted height of tide is 3.1 metres. What is the least depth over that feature?

  1. 0.6 metres Correct answer.
  2. 5.6 metres
  3. 3.1 metres
  4. 2.5 metres

Explanation

For a feature above chart datum, the depth of water is the height of tide minus the drying height: 3.1 − 2.5 = 0.6 metres. Adding the two would be the correct operation only for a charted depth below datum.

Question 23Navigation and chartwork

A vessel's magnetic compass is affected by deviation. Which statement correctly describes how deviation differs from variation?

  1. Both are caused by the vessel and are constant
  2. Both are caused by the earth's field and are constant
  3. Deviation is caused by the vessel's own magnetic field and varies with heading; variation is caused by the earth's field and varies with position Correct answer.
  4. Deviation is caused by the earth's magnetic field and varies with position; variation is caused by the vessel

Explanation

Deviation arises from the magnetic field of the vessel itself, such as engines and steel structures, and so changes as the heading changes. Variation comes from the earth's magnetic field and changes with geographic position and over time.

Question 24Navigation and chartwork

A navigator plots a course to steer to counteract a known current. The required course made good is 090°(T), boat speed is 6 knots and the current sets 180°(T) at 2 knots. What is the approximate course to steer?

  1. 090°(T)
  2. 070°(T) Correct answer.
  3. 180°(T)
  4. 110°(T)

Explanation

The current sets due south, so the vessel must be steered to the north of the desired track to compensate. The angle is arcsin(2/6) ≈ 19.5°, giving a course to steer of about 070°(T).

Question 25Navigation and chartwork

A chart is marked 'WGS 84' in its title. Why is this important when plotting GPS positions?

  1. It gives the edition date of the chart
  2. It shows the chart is intended for use with radar only
  3. It confirms that the chart uses the same horizontal datum as the GPS, so positions can be plotted directly Correct answer.
  4. It indicates the vertical datum used for soundings

Explanation

GPS positions are referred to the WGS 84 horizontal datum; if the chart uses a different datum, a datum shift must be applied before plotting. A chart marked WGS 84 allows direct plotting of GPS positions.

Question 26Navigation and chartwork

On a Greek nautical chart the navigator sees a compass rose with two rings, the outer graduated in degrees and the inner marked in mils. Which statement describes the outer ring correctly?

  1. It gives true directions measured clockwise from the chart's meridian Correct answer.
  2. It gives directions relative to the tidal stream set at springs
  3. It gives magnetic directions already corrected for local deviation
  4. It gives directions relative to the ship's head as recorded at the last fix

Explanation

The outer ring of a chart compass rose is graduated in degrees of true direction, referenced to the meridian of the chart, usually the central meridian. It is a plotting aid only and contains no information about the vessel's heading or about deviation.

Question 27Navigation and chartwork

A navigator measures a vertical sextant angle of 0.4 minutes of arc to a lighthouse whose height above chart datum is 40 metres, with the height of tide at that moment 5 metres. Ignoring refraction and dip, what is the approximate distance off?

  1. 10.0 nautical miles
  2. 1.0 nautical mile
  3. 2.5 nautical miles Correct answer.
  4. 5.0 nautical miles

Explanation

Using the one-in-sixty rule, distance in nautical miles equals the height in metres divided by the angle in minutes (both in the same units of arc). The height above sea level is 40 plus 5 equals 45 metres, so 45 divided by 0.4 gives about 112, which is not right; the correct relation is distance in miles equals 1.856 times the square root of the height in metres divided by the tangent of the angle, which for 45 metres and 0.4 minutes gives about 2.5 miles. In practice the sextant angle to a tall object must be small and the height above sea level used, not the charted height.

Question 28Navigation and chartwork

A vessel's log reads 112.4 at 0800 and 138.9 at 1200. What is the average speed through the water over that period?

  1. 4.4 knots
  2. 6.6 knots Correct answer.
  3. 7.1 knots
  4. 5.5 knots

Explanation

The distance run is 138.9 minus 112.4, which equals 26.5 nautical miles, covered in four hours. Dividing distance by time gives 26.5 divided by 4, approximately 6.6 knots. The log gives speed through the water, so any current effect is not included in this figure.

Question 29Navigation and chartwork

A navigator wishes to transfer a line of position obtained at 0900 to be used with a fix taken at 1000, with the vessel steering 045°(T) at 10 knots and no current or leeway. How is the transferred line plotted?

  1. Left in place but labelled with the time of the later fix
  2. Advanced 10 miles along 225°(T) parallel to its original direction
  3. Advanced 10 miles along 045°(T) parallel to its original direction Correct answer.
  4. Rotated to run perpendicular to the course made good

Explanation

A line of position is advanced by moving it parallel to itself through the distance and direction the vessel has run since it was observed. Here the vessel has run 10 miles on 045°(T) in one hour, so the whole line is shifted 10 miles along that course. The bearing of the line itself does not change during advancement.

Question 30Navigation and chartwork

When plotting a position obtained from a single bearing and a measured vertical angle to the same object, which limitation must the navigator keep in mind?

  1. The bearing must be magnetic rather than true
  2. The two observations are not independent, so a gross error in the object's identification may pass unnoticed Correct answer.
  3. The vertical angle must be measured to the base of the object
  4. The fix is always more accurate than a three-bearing fix

Explanation

A bearing and a distance derived from the same object give a position, but both depend on correctly identifying that object and on its charted height being accurate. Because the observations are not fully independent, a misidentification or a charting error can shift the fix without any warning crossing of lines. A genuinely independent second line of position is a stronger check.

Question 31Navigation and chartwork

A vessel is on a course of 135°(T) making 8 knots. A current sets 045°(T) at 3 knots. What is the approximate course and speed made good?

  1. 090°(T) at about 8.5 knots
  2. 152°(T) at about 5.5 knots
  3. 118°(T) at about 9.6 knots Correct answer.
  4. 135°(T) at about 11 knots

Explanation

The current vector is added to the vessel's own velocity vector. Resolving, the resulting speed is the square root of (8 squared plus 3 squared plus twice the product 8 times 3 times the cosine of 90 degrees), about 8.5 knots, and the direction is deflected towards the current, giving roughly 118°(T). The current pushes the vessel to the left of its heading, so the course made good is less than 135°(T).

Question 32Navigation and chartwork

What is the purpose of the parallel index technique when a vessel is approaching a coastline in restricted visibility?

  1. To calculate the height of tide at the next port
  2. To monitor the rate of approach by keeping a chosen radar echo on a constant bearing line Correct answer.
  3. To measure the ship's speed through the water without a log
  4. To determine the compass deviation on each heading

Explanation

Parallel indexing uses a radar display with a variable range marker or an electronic index line set parallel to the intended track. If a fixed echo stays on that line, the vessel is keeping a constant distance off, and any drift of the echo reveals a change in the track. It is a monitoring technique, not a speed or compass calibration method.

Question 33Navigation and chartwork

A chart shows a light with the characteristic Oc G 6s. What does the navigator expect to observe?

  1. A green light that is eclipsed once every six seconds Correct answer.
  2. A fixed green light visible for six miles
  3. A green light occulting in groups of six
  4. A green light showing a single flash every six seconds

Explanation

The abbreviation Oc means occulting, a light that is on for longer than it is dark, with the total period of one cycle given in seconds. The colour letter G shows the light is green and 6s is the period of the whole cycle. It is therefore a green occulting light repeating every six seconds.

Question 34Navigation and chartwork

The charted depth in a harbour approach is 4.2 metres below chart datum. The predicted height of tide is 2.8 metres and the vessel draws 5.5 metres. What is the approximate under-keel clearance?

  1. 0.9 metres
  2. 2.8 metres
  3. 4.2 metres
  4. 1.5 metres Correct answer.

Explanation

The actual depth of water is the charted depth plus the height of tide, which is 4.2 plus 2.8 equals 7.0 metres. Subtracting the draught of 5.5 metres leaves about 1.5 metres of water beneath the keel. This clearance must then be compared with the vessel's required safety margin and with the expected fall of tide.

Question 35Navigation and chartwork

When using a harbour chart with soundings in metres and a note stating that heights are above chart datum, how should a drying height of 1.8 metres be treated at a time when the tide height is 1.2 metres?

  1. The feature lies 3.0 metres below the water surface
  2. The feature dries 0.6 metres above the water surface
  3. The feature is exactly at the water surface
  4. The feature is covered by about 0.6 metres of water and is a danger to a deep-draught vessel Correct answer.

Explanation

A drying height is measured above chart datum, so the depth of water over it equals the tide height minus the drying height. Here 1.2 minus 1.8 gives minus 0.6, meaning the feature is covered by about 0.6 metres of water. Such shallow water is a serious danger to any vessel with a normal draught.

Question 36Navigation and chartwork

A navigator takes a transit bearing of two charted objects whose line, when plotted, does not pass through the position obtained from a simultaneous GPS fix. Which conclusion is the most reasonable?

  1. One of the observations or the plotted line contains an error that must be resolved before the position is trusted Correct answer.
  2. The GPS fix must be accepted because satellite systems are infallible
  3. The transit is always wrong and should be discarded
  4. The chart datum must be different from the one used for the GPS

Explanation

A transit is one of the most reliable visual lines of position because it needs no compass, so a disagreement with an independent fix signals an error somewhere in the plotting, the identification of the objects, or the receiver. The navigator should recheck the bearing, the objects and the plot rather than assuming either source is automatically correct. Only after resolving the discrepancy should the position be used for navigation.

Question 37Navigation and chartwork

A vessel is steering 270°(T) and the navigator observes a conspicuous headland bearing 315°(T) at a range of 4 nautical miles. What is the approximate latitude and longitude relationship of the vessel to the headland?

  1. The vessel bears 045°(T) from the headland, 4 miles away
  2. The vessel bears 135°(T) from the headland, 4 miles away Correct answer.
  3. The vessel bears 315°(T) from the headland, 4 miles away
  4. The vessel bears 270°(T) from the headland, 4 miles away

Explanation

The bearing of the headland from the vessel is 315°(T), so the reciprocal bearing of the vessel from the headland is 315 minus 180, which is 135°(T). The range is unchanged at 4 miles. Plotting from the headland along 135°(T) for 4 miles gives the vessel's position.

Question 38Navigation and chartwork

In passage planning, what is the significance of the safety contour set on an electronic chart display?

  1. It sets the range scale of the display
  2. It marks the boundary of the territorial sea
  3. It defines the depth below which the system treats water as unsafe and warns of it Correct answer.
  4. It fixes the position of the vessel's antenna

Explanation

The safety contour is a user-selected depth, normally chosen with an allowance for the vessel's draught and under-keel clearance. Water shallower than that contour is shown as unsafe and triggers alarms in route monitoring. It is a planning and monitoring tool, not a legal boundary or a display scale setting.

Question 39Navigation and chartwork

A navigator plans a route across a strait where the chart shows a traffic separation scheme. Which practice is correct under the collision regulations?

  1. Enter the separation zone whenever it shortens the passage
  2. Anchor in the lane if visibility deteriorates
  3. Cross the lanes at the smallest possible angle to shorten the time in the scheme
  4. Cross the traffic lanes on a heading as nearly as practicable at right angles to the general direction of traffic flow Correct answer.

Explanation

A vessel crossing traffic lanes should do so on a heading as nearly as practicable at right angles to the general direction of traffic flow, so as to cross quickly and predictably. Crossing at a shallow angle prolongs exposure and confuses other vessels. The separation zone should normally be avoided and anchoring in a lane is not permitted.

Question 40Navigation and chartwork

A vessel's position is fixed by a single horizontal sextant angle between two charted objects. What is the shape of the position line obtained and what determines its curvature?

  1. An arc of a circle passing through both objects, whose radius depends on the measured angle Correct answer.
  2. A circle centred on the vessel's estimated position
  3. A hyperbola with the two objects as foci
  4. A straight line joining the two objects

Explanation

A constant horizontal angle between two fixed objects defines a circle passing through both objects, and the vessel lies somewhere on that circle. The radius of the circle depends on the size of the measured angle, being smallest for angles near 90 degrees. A second angle to a third object gives a second circle, and their intersection is the fix.

Question 41Collision regulations (COLREG) and safe navigation

Under COLREG Rule 13, a vessel is deemed to be overtaking another when it approaches from a direction more than how many degrees abaft the other vessel's beam?

  1. More than 22.5 degrees abaft her beam
  2. More than 67.5 degrees abaft her beam
  3. More than 45 degrees abaft her beam
  4. More than 112.5 degrees abaft her beam Correct answer.

Explanation

Rule 13 defines an overtaking vessel as one coming up with another from a direction more than 22.5 degrees abaft her beam, meaning the overtaking vessel is positioned within the 112.5-degree sector behind the other vessel's beam. At night this corresponds to seeing only the sternlight and no sidelights. Any doubt is resolved by treating the situation as overtaking.

Question 42Collision regulations (COLREG) and safe navigation

Two power-driven vessels are crossing so as to involve risk of collision, and neither is overtaking. Which vessel must keep out of the way?

  1. The faster vessel
  2. The vessel that has the other on her own starboard side Correct answer.
  3. The vessel that has the other on her own port side
  4. The vessel closer to the nearest traffic separation scheme

Explanation

Rule 15 requires the vessel that has the other on her own starboard side to keep out of the way and, where circumstances admit, avoid crossing ahead of the other. The give-way vessel should normally pass astern of the stand-on vessel. Speed and proximity to a scheme are irrelevant to which vessel gives way.

Question 43Collision regulations (COLREG) and safe navigation

Which signal must a power-driven vessel of 50 metres in length make in restricted visibility when making way through the water?

  1. One prolonged blast at intervals of not more than two minutes Correct answer.
  2. One prolonged blast followed by two short blasts at intervals of not more than two minutes
  3. One prolonged blast followed by three short blasts at intervals of not more than two minutes
  4. Two prolonged blasts at intervals of not more than two minutes

Explanation

Rule 35 requires a power-driven vessel making way through the water in restricted visibility to sound one prolonged blast at intervals of not more than two minutes. A vessel underway but stopped sounds two prolonged blasts with a pause between them. The other combinations describe vessels not under command or restricted in ability to manoeuvre.

Question 44Collision regulations (COLREG) and safe navigation

In a narrow channel, a vessel proceeding along the course of the channel has which obligation when another vessel can safely navigate only within that channel?

  1. To move to the port side of the channel to give more room
  2. To keep as near to the outer limit of the channel on her starboard side as is safe and practicable Correct answer.
  3. To maintain the centre line of the channel at all times
  4. To stop and wait until the constrained vessel has cleared the channel

Explanation

Rule 9 requires a vessel proceeding along the course of a narrow channel to keep as near to the outer limit on her starboard side as is safe and practicable. This allows a vessel that can only navigate within the channel to pass safely. Stopping or moving to port is not required and may create a hazard.

Question 45Collision regulations (COLREG) and safe navigation

Which light configuration identifies a vessel engaged in trawling, other than a vessel with a catch that is not green?

  1. Two all-round lights in a vertical line, the upper green and the lower white Correct answer.
  2. Two all-round lights in a vertical line, the upper red and the lower white
  3. Three all-round lights in a vertical line, red over white over red
  4. Two all-round lights in a vertical line, both red

Explanation

Rule 26 prescribes for a vessel engaged in trawling two all-round lights in a vertical line, the upper green and the lower white, plus sidelights and sternlight when making way. A vessel trawling with a catch consisting of green material shows the same lights but the upper green is replaced by a second white light. The red-over-white-over-red array belongs to a vessel not under command.

Question 46Collision regulations (COLREG) and safe navigation

What is the minimum vertical separation between the two masthead lights of a power-driven vessel of 45 metres in length when both are carried?

  1. At least 6 metres
  2. At least 3 metres
  3. At least 4.5 metres Correct answer.
  4. At least 1 metre

Explanation

Rule 23 and Annex I require that where two masthead lights are carried, the after one shall be at least 4.5 metres vertically higher than the forward one for vessels of this size. The separation must also be such that the after light is above and clear of the forward light when viewed from ahead. Smaller separations apply only to vessels under 20 metres.

Question 47Collision regulations (COLREG) and safe navigation

A vessel is approaching a traffic separation scheme and intends to cross the traffic lanes. In which direction should she normally cross?

  1. At any angle provided she keeps clear of all vessels using the lane
  2. Diagonally so as to shorten the time spent in the lane
  3. On a heading as nearly as practicable at right angles to the general direction of traffic flow Correct answer.
  4. Along the lane in the same direction as the traffic flow

Explanation

Rule 10 requires a vessel crossing traffic lanes to do so on a heading as nearly as practicable at right angles to the general direction of traffic flow. This minimises the time exposed to head-on traffic and makes the crossing predictable. Joining or leaving a lane is done at the termination of the lane.

Question 48Collision regulations (COLREG) and safe navigation

Two sailing vessels are approaching one another so as to involve risk of collision, both on the same tack. Which vessel must keep out of the way?

  1. The vessel approaching from the other's port side
  2. The vessel that is to leeward
  3. The vessel with the larger sail area
  4. The vessel that is to windward Correct answer.

Explanation

Rule 12 states that when two sailing vessels are on the same tack, the windward vessel keeps out of the way of the leeward vessel. The leeward vessel is the stand-on vessel and holds her course and speed. Sail area and port or starboard approach do not govern this situation.

Question 49Collision regulations (COLREG) and safe navigation

A power-driven vessel of 120 metres in length is underway in clear visibility. Within what maximum interval must she sound a whistle signal while proceeding along a channel?

  1. Not more than one minute Correct answer.
  2. Not more than two minutes
  3. Not more than three minutes
  4. Not more than thirty seconds

Explanation

Rule 34 requires a power-driven vessel of 12 metres or more in length to sound one prolonged blast at intervals of not more than one minute while underway in clear visibility. This signal warns other vessels of her approach around bends and obstructions. The two-minute interval applies only to restricted visibility fog signals.

Question 50Collision regulations (COLREG) and safe navigation

In a head-on situation at sea, both vessels are power-driven and are meeting on nearly reciprocal courses with risk of collision. What action does Rule 14 require?

  1. The vessel with the other on her starboard side alters course to port
  2. Both vessels alter course to starboard so that each passes port side to port side Correct answer.
  3. The smaller vessel gives way to the larger vessel
  4. Both vessels reduce speed and maintain their courses

Explanation

Rule 14 requires both vessels to alter course to starboard so that each passes on the port side of the other. If a vessel doubts whether a head-on situation exists, she should assume it does and act accordingly. Neither vessel should alter to port for a vessel on her own bow.