Colreg 4, Annexes

Q. On a power-driven vessel of 20 metres or more in length, what is the height of masthead above hull?
Ans. The forward masthead light, or if only one masthead light is carried, then that light, is placed at a height above the hull of not less than 6 metres, and, if the breadth of the vessel exceeds 6 metres, then at a height above the hull not less than such breadth, so however that the light need not be placed at a greater height above the hull than 12 m.

H < 6m
If breadth > 6m then H < B
H need not be > 12m

Q. What must be the vertical separation of aft mast head light?
Ans. 1. When two masthead lights are carried the after one shall be at least 4.5 metres vertically higher than the forward one.
2. The vertical separation of masthead lights of power-driven vessels shall be such that in all normal conditions of trim the after light will be seen over and separate from the forward light at a distance of 1000 metres from the stem when viewed from sea-level.

Q. If height of foremost light is 15m above w/level and distance between mast lights is 60m. Foremast light at 20m from STEM. Find height of aft mast light above w/l to be clearly visible above foremast light. Ship’s length is 110m.

Ans. Adequately more than 15.88m.

Q. What is the additional separation if ship was trimmed, 4m by aft?
Ans. Main mast is lowered due stern trim. This can be found as follows:

Now the minimum vertical separation required = 2.18 + 0.88 = 3.06m.

Q. On a power-driven vessel of less than 12 metres in length, if a masthead light or an all round light is carried in addition to sidelights and a sternlight, what height difference is maintained?
Ans. The masthead light or all-round light shall be carried at least 1 metre higher than the sidelights.

Q. Can the side lights be placed higher than masthead lights?
Ans. The sidelights of a power-driven vessel shall be placed at a height above the hull not greater than three quarters of that of the forward masthead light. They shall not be so low as to be interfered with by deck lights.

Q. On a vessel of 20m or more in length, when two or three lights are carried in a vertical line, how will they be spaced?
Ans. Such lights shall be spaced not less than 2 metres apart, and the lowest of these lights shall, except where a towing light is required, be placed at a height of not less than 4 metres above the hull. When three lights are carried they shall be equally spaced.
The lower of the two all-round lights prescribed for a vessel when engaged in fishing shall be at a height above the sidelights not less than twice the distance between the two vertical lights. The forward anchor light when two are carried, shall not be less than 4.5 metres above the after one. On a vessel of 50 metres or more in length this forward anchor light shall be placed at a height of not less than 6 metres above the hull.

Q. What is the rule regarding horizontal positioning of masthead lights?
Ans. When two masthead lights are prescribed for a power-driven vessel, the horizontal distance between them shall not be less than one half of the length of the vessel but need not be more than 100 metres. The forward light shall be placed not more than one quarter of the length of the vessel from the stem.

Q. How are the screens of sidelights fitted?
Ans. The sidelights of vessels of 20 metres or more in length shall be fitted with inboard screens painted matt black, and meeting the requirements of section 9 of this Annex. . In the forward direction, sidelights as fitted on the vessel shall show the minimum required intensities. The intensities shall decrease to reach practical cut-off between 1 degree and 3 degrees outside the prescribed sectors. For sternlights and masthead lights and at 22.5° abaft the beam for sidelights, the minimum required intensities shall be maintained over the arc of the horizon up to 5 degrees within the limits of the sectors prescribed in Rule 21. From 5 degrees within the prescribed sectors the intensity may decrease by 50 per cent up to the prescribed limits; it shall decrease steadily to reach practical cut-off at not more than 5 degrees outside the prescribed sectors.

Q. What sizes are prescribed for shapes?
Ans. For the ship of length 20m or more,
(i). a ball shall have a diameter of not less than 0.6 metre;
(ii). a cone shall have a base diameter of not less than 0.6 metre and a height equal to its diameter;
(iii). a cylinder shall have a diameter of at least 0.6 metre and a height of twice its diameter;
(iv). a diamond shape shall consist of two cones as defined in (ii) above having a common base.

Q. What is the provision about vertical sectors?
Ans. (a) The vertical sectors of electric lights as fitted, with the exception of lights on sailing vessels underway shall ensure that:
(i) at least the required minimum intensity is maintained at all angles from 5 degrees above to 5 degrees below the horizontal;
(ii) at least 60 per cent of the required minimum intensity is maintained from 7.5 degrees above to 7.5 degrees below the horizontal.

(b) In the case of sailing vessels underway the vertical sectors of electric lights as fitted shall ensure that:
(i) at least the required minimum intensity is maintained at all angles from 5 degrees above to 5 degrees below the horizontal;
(ii) at least 50 per cent of the required minimum intensity is maintained from 25 degrees above to 25 degrees below the horizontal.

Q. What is the provision about maneuvering light?
Ans. The maneuvering light described in Rule 34(b) shall be placed in the same fore and aft vertical plane as the masthead light or lights and, where practicable, at a minimum height of 2 metres vertically above the forward masthead light, provided that it shall be carried not less than 2 metres vertically above or below the after masthead light. On a vessel where only one masthead light is carried the manoeuvring light, if fitted, shall be carried where it can best be seen, not less than 2 metres vertically apart from the masthead light.

Q. What is the provision about directional properties of sound signal?
Ans. The sound pressure level of a directional whistle shall be not more than 4 dB below the prescribed sound pressure level on the axis at any direction in the horizontal plane within ± 45 degrees of the axis. The sound pressure level at any other direction in the horizontal plane shall be not more than 10 dB below the prescribed sound pressure level on the axis, so that the range in any direction will be at least half the range on the forward axis. The sound pressure level shall be measured in that 1/3rd-octave band which determines the audibility range.

Q. What is the provision about positioning of whistles?
Ans. When a directional whistle is to be used as the only whistle on a vessel, it shall be installed with its maximum intensity directed straight ahead. . A whistle shall be placed as high as practicable on a vessel, in order to reduce interception of the emitted sound by obstructions and also to minimize hearing damage risk to personnel. The sound pressure level of the vessel’s own signal at listening posts shall not exceed 110 dB (A) and so far as practicable should not exceed 100 dB (A).
If whistles are fitted at a distance apart of more than 100 metres, it shall be so arranged that they are not sounded simultaneously.

Q. What is the provision regarding construction of bell and gong?
Ans. Bells and gongs shall be made of corrosion-resistant material and designed to give a clear tone. The diameter of the mouth of the bell shall be not less than 300 mm for vessels of 20 metres or more in length. Where practicable, a power driven bell striker is recommended to ensure constant force but manual operation shall be possible. The mass of the striker shall be not less than 3 per cent of the mass of the bell.

Q. What are the various distress signals prescribed in Annex IV?
1. The following signals, used or exhibited either together or separately, indicate distress and need of assistance:
(a) a gun or other explosive signal fired at intervals of about a minute;
(b) a continuous sounding with any fog-signalling apparatus;
(c) rockets or shells, throwing red stars fired one at a time at short intervals;
(d) a signal made by radiotelegraphy or by any other signalling method consisting of the group …—… (SOS) in the Morse Code;
(e) a signal sent by radiotelephony consisting of the spoken word “Mayday”;
(f) the International Code Signal of distress indicated by N.C.;
(g) a signal consisting of a square flag having above or below it a ball or anything resembling a ball;
(h) flames on the vessel (as from a burning tar barrel, oil barrel, etc.);
(i) a rocket parachute flare or a hand-flare showing a red light;
(j) a smoke signal giving off orange-coloured smoke;
(k) slowly and repeatedly raising and lowering arms outstretched to each side;
(l) the radiotelegraph alarm signal;
(m) the radiotelephone alarm signal;
(n) signals transmitted by emergency positioning-indicating radio beacons;
(o) approved signals transmitted by radiocommunication systems, including survival craft radar transponders.

Q. What is the minimum height of a masthead light prescribed for a small power driven vessel?
Ans. The masthead light of a power-driven vessel of 12 metres but less than 20 metres in length shall be placed at a height above the gunwale of not less than 2.5 metres.

Q. Can the two or 3 mast lights required in case of towing be placed on fore mast?
Ans. One of the two or three masthead lights prescribed for a power-driven vessel when engaged in towing or pushing another vessel shall be placed in the same position as either the forward masthead light or the after masthead light; provided that, if carried on the aftermast, the lowest after masthead light shall be at least 4.5 metres vertically higher than the forward masthead light.

Q. When exhibiting the all round lights for vessel restricted in ability to maneuvers or vessel constrained by draft, what is the regulation in respect of vertical positioning wrt masthead lights?
Ans. When it is impracticable to carry the all-round lights prescribed by Rule 27(b)(i) or Rule 28 below the masthead lights, they may be carried above the after masthead light(s) or vertically in between the forward masthead light(s) and after masthead light(s), provided that in the latter case the requirement of section 3(c) of this Annex shall be complied with. 3(c) being: ‘when the lights prescribed in Rule 27(b)(i) or Rule 28 are placed vertically between the forward masthead light(s) and the after masthead light(s) these all-round lights shall be placed at a horizontal distance of not less than 2 metres from the fore and aft centreline of the vessel in the athwartship direction.

Three possible locations of RAM & CBD lights.

Q. What is the minimum vertical separation required for the all round red over white light prescribed for a vessel engaged in fishing?
Ans. The lower of the two all-round lights prescribed for a vessel when engaged in fishing shall be at a height above the sidelights not less than twice the distance between the two vertical lights.