Handbook of the Nautical Rules of the Road by Llana & Wisneskey

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Annex I -- Positioning and Technical Details of Navigation Lights (continued)


This is the continuation of Annex I.


INTERNATIONAL

INLAND

5. Screens for sidelights

The sidelights of vessels 20 meters or more in length shall be fitted with inboard screens painted matt black, and meeting the requirements of Section 9 of this Annex. On vessels of less than 20 meters in length the sidelights, if necessary to meet the requirements of Section 9 of this Annex, shall be fitted with inboard matt black screens. With a combined lantern, using a single vertical filament and a very narrow division between the green and red sections, external screens need not be fitted.

§ 84.09 Screens

(a) The sidelights of vessels 20 meters or more in length shall be fitted with mat black inboard screens and meet the requirements of § 84.17. On vessels of less than 20 meters in length, the sidelights, if necessary to meet the requirements of § 84.17, shall be fitted with mat black inboard screens. With a combined lantern, using a single vertical filament and a very narrow division between the green and red sections, external screens need not be fitted.

 

The sidelights on vessels twenty meters or more long must be fitted with screens, which are used to keep the light from being seen across the bow (or, in other words, to help the sidelights meet the horizontal sector cut-off requirements of Annex I). In practice, some sidelights meet the cut-off requirements (see Section 9/§ 84.17) without screens, but screens must still be fitted. The length of the screens is not specified, so they may be very short if not needed to meet other requirements.

Rule 21 permits vessels less than twenty meters long to combine their sidelights into one lantern using a single filament as the light source. Many of these lights are constructed with the green lens and the red lens butted together (often glued together to keep out moisture and prevent light leaks). Since a vertical filament will be parallel with the lens joint, the transition from green to red will be almost instant rather than gradual, and therefore a screen is not needed.

Technology marches forward, even in the maritime industry, and with the inefficient incandescent lamp giving way to modern light sources such as LED, it is only a matter of time before this rule will have to be re-interpreted.


INLAND

(b)On power-driven vessels less than 12 meters in length, constructed after July 31, 1983, the masthead light, or the all-round light described in Rule 23(c) shall be screened to prevent direct illumination of the vessel forward of the operator's position.

 

The Inland version of the section on screens also contains a provision for screening navigation lights to prevent them from shining down on the boat where the glare would impair the operator's night vision.


INTERNATIONAL

INLAND

6. Shapes

(a) Shapes shall be black and of the following sizes:

(i) a ball shall have a diameter of not less than 0.6 meter;

(ii) a cone shall have a base diameter of not less than 0.6 meter and a height equal to its diameter;

(iii) a cylinder shall have a diameter of at least 0.6 meter 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.

(b) The vertical distance between shapes shall be at least 1.5 meter.

(c) In a vessel of less than 20 meters in length shapes of lesser dimensions but commensurate with the size of the vessel may be used and the distance apart may be correspondingly reduced.

§ 84.11 Shapes

(a) Shapes shall be black and of the following sizes:

(1) A ball shall have a diameter of not less than 0.6 meter;

(2) A cone shall have a base diameter of not less than 0.6 meter and a height equal to its diameter;

(3) A diamond shape shall consist of two cones (as defined in Paragraph (a)(2) of this section) having a common base.

(b) The vertical distance between shapes shall be at least 1.5 meter.

(c) In a vessel of less than 20 meters in length shapes of lesser dimensions but commensurate with the size of the vessel may be used and the distance apart may be correspondingly reduced.

 

The minimum distance between shapes displayed in a vertical line is one and a half meters. This is measured from the top of one shape to the bottom of the one above it.

The size and spacing of shapes for small vessels may be less than specified in Annex I but not too much less. A vessel nineteen meters long would certainly not be justified in displaying shapes one-half normal size, although an eight meter vessel would.


INTERNATIONAL

INLAND

7. Color specification of lights

The chromaticity of all navigation lights shall conform to the following standards, which lie within the boundaries of the area of the diagram specified for each color by the International Commission on Illumination (CIE).

The boundaries of the area for each color are given by indicating the corner coordinates, which are as follows:

(i) White:

x 0.525 0.525 0.452 0.310 0.310 0.443

y 0.382 0.440 0.440 0.348 0.283 0.382

(ii) Green:

x 0.028 0.009 0.300 0.203

y 0.385 0.723 0.511 0.356

(iii) Red

x 0.680 0.660 0.735 0.721

y 0.320 0.320 0.265 0.259

(iv) Yellow

x 0.612 0.618 0.575 0.575

y 0.382 0.382 0.425 0.406

§ 84.13 Color specification of lights

(a) The chromaticity of all navigation lights shall conform to the following standards, which lie within the boundaries of the area of the diagram specified for each color by the International Commission on Illumination (CIE), in the "Colors of Light Signals," which is incorporated by reference. It is Publication CIE No. 2.2. (TC-16), 1975, and is available from the Illumination Engineering Society, 345 East 47th Street, New York, NY 10017. It is also available for inspection at the Office of the Federal Register, Room 8401, 1100 L Street N.W., Washington, DC 20408. This incorporation by reference was approved by the Director of the Federal Register.

(b) The boundaries of the area for each color are given by indicating the corner coordinates, which are as follows:

(1) White:

x 0.525 0.525 0.452 0.310 0.310 0.443

y 0.382 0.440 0.440 0.348 0.283 0.382

(2) Green:

x 0.028 0.009 0.300 0.203

y 0.385 0.723 0.511 0.356

(3) Red

x 0.680 0.660 0.735 0.721

y 0.320 0.320 0.265 0.259

(4) Yellow

x 0.612 0.618 0.575 0.575

y 0.382 0.382 0.425 0.406

 

This section of Annex I is for the manufacturers of navigation lights and their lenses. The chromaticity of navigation lights is also affected by the lamp used and by the voltage at which it is operated. The numbers given describe the exact shade and hue of green, yellow, red, and white light required. The color measurements are made using the lanp and voltage for which the navigation light is designed.


INTERNATIONAL

INLAND

8. Intensity of lights

(a) The minimum luminous intensity of lights shall be calculated by using the following formula:

(b) A selection of figures derived from the formula is given in the following table:

Note: The maximum luminous intensity of navigation lights should be limited to avoid undue glare. This shall not be achieved by a variable control of the luminous intensity.

§ 84.15 Intensity of lights

(a) The minimum luminous intensity of lights shall be calculated by using the following formula:

(b) A selection of figures derived from the formula is given in Table 84.15(b):

Table 84.15 (b)

 

This section gives the minimum required light intensities (measured in candelas) corresponding to ranges of visibility at a standard atmospheric clearness. The required range of visibility for any particular navigation light is given in Rule 22. This section is another used by the manufacturer of navigation lights.

A note at the end of the International version of this section cautions against lights that are so bright that they impair the night vision of the vessel's operator or lookout. Because this is a suggestion ("should") and not a requirement, it is not contained in the regulatory Inland Annex I.

The International Rule proscription against a variable voltage control to vary light intensity is not contained in the Inland version because of a different philosophy: a device that would permit an increase in intensity in open water or when the air is not so clear, but which could not be manipulated to reduce the intensity below the minimum required, would be an advantage.


INTERNATIONAL

INLAND

9. Horizontal sectors

(a)(i) 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.

(ii) For sternlights and masthead lights and at 22.5 degrees 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 percent up to the prescribed limits; it shall decrease steadily to reach practical cut-off at not more than 5 degrees outside the prescribed sectors.

§ 84.17 Horizontal sectors

(a)(1) 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 and 3 degrees outside the prescribed sectors.

(2) For sternlights and masthead lights and at 22.5 degrees 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 percent up to the prescribed limits; it shall decrease steadily to reach practical cut-off at not more than 5 degrees outside the prescribed sectors.

 


INTERNATIONAL

INLAND

(b)(i) All-round lights shall be so located as not to be obscured by masts, topmasts or structures wuthin angular sectors of more tha 6 degrees, except anchor lights prescribed in Rule 30, which need not be placed at an impracticable height above the hull.

(ii) If it is impracticable to comply with paragrph (b)(i) of this section by exhibiting only one all-round light, two all-round lights shall be used suitably positioned or screened so that they appear, as far as practicable, as one light at a distance of one mile.

(b) All-round lights shall be so located as not to be obscured by masts, topmasts or structures wuthin angular sectors of more tha 6 degrees, except anchor lights prescribed in Rule 30, which need not be placed at an impracticable height above the hull, and the all-round white light described in Rule 23(d), which may not be obscured at all.

(c) If it is impracticable to comply with paragrph (b) of this section by exhibiting only one all-round light, two all-round lights shall be used suitably positioned or screened to appear, as far as practicable, as one light at a minimum distance of one nautical mile.

Note to paragraph (c): Two unscreened all-round lights that are 1.28 meters apart or less will appear as one light to the naked eye at a distance of one nautical mile.

 

This provision accommodates vessels that, for practical reasons (large diameter mast, etc.), cannot mount a single all-round light so that less than six degrees of arc is obstructed.

A "horizontal sector," defined earlier, refers to the arc around the horizon through which each navigation light is supposed to shine. The sectors are described as being part of a circle divided into 360 degrees and having reference points directly ahead, directly aft, and abeam on each side. The theoretical sectors through which each navigation light is to be seen are given in Rule 21.

The actual sectors and corresponding intensities are given here in Annex I. The best way to see how a navigation light conforms to horizontal sector requirements is to plot the light intensity against sector angle. "Practical cut-off" is defined for vessels twenty meters or longer in the first section of the Inland Annex I. The United States uses the same definition for International Rule navigation lights it approves, but other countries may define the term in other ways.

All-round lights do not have sector boundaries, but may in some cases have part of their light cut off by interfering masts, topmasts, or other structures. All-round lights, such as those that indicate a vessel engaged in fishing or a vessel restricted in ability to maneuver, may be obscured for up to a total of 6 degrees. Anchor lights may be mounted relatively low (especially the after one) and be hidden by the vessel's superstructure through more than six degrees of arc. At least one of the two anchor lights should be visible from all around the horizon. If a small vessel displays only one anchor light, you should take care to minimize obscuration, even though you are not limited to six degrees.

Small vessels are permitted to display an all-round light in lieu of masthead light and sternlight. If this all-round light is used, it must be mounted where it will not be obscured at all. This latter requirement is implicit in the International version; the masthead light and sternlight the all-round light replaces may not be obscured. (The International Rules before 1983 did not permit the all-round light substitution, and when the Rules were amended, the corresponding Annex I clarifications were overlooked.)


INTERNATIONAL

INLAND

10. Vertical sectors

(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 the horizontal;

(ii) at least 60 percent 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 percent of the required minimum intensity is maintained from 25 degrees above to 25 degrees below the horizontal.

(c) In the case of lights other than electric these specifications shall be met as closely as possible.

§ 84.19 Vertical sectors

(a) The vertical sectors of electric lights as fitted, with the exception of lights on sailing vessels underway and on unmanned barges, shall ensure that:

(1) At least the required minimum intensity is maintained at all angles from 5 degrees above to 5 degrees below the the horizontal;

(2) At least 60 percent 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:

(1) At least the required minimum intensity is maintained at all angles from 5 degrees above to 5 degrees below the horizontal;

(2) At least 50 percent of the required minimum intensity is maintained from 25 degrees above to 25 degrees below the horizontal.

(c) In the case of unmanned barges the minimum required intensity of electric lights as fitted shall be maintained on the horizontal.

(d) In the case of lights other than electric these specifications shall be met as closely as possible.

 

It is possible to design the lens of a navigation light so that all of the light is focused into a narrow band shining out in a horizontal plane. This would be very efficient and effective as long as the navigation light (and attached vessel) stay level. As soon as the vessel heels or pitches, however, a narrow light beam would shine up into the sky on one side and down into the water on the other. For observers on nearby vessels, the light would disappear.

Navigation lights must therefore shine above and below the horizontal. Sailboats normally heel more than power-driven vessels, so lights for sailing vessels have a greater vertical dispersion requirement. This special requirement does not, however, apply to sailing vessels that are anchored, for instance; the paragraph (b) technical specifications for sailing vessels apply only to those lights displayed while underway (Rule 25 lights).

While power-driven vessels do not normally heel as much as sailing vessels, they often pitch up from their at-rest attitude when moving (we're talking about smaller vessels, not tankers). If, for example, the masthead light is mounted parallel to the deck and the deck is angled 15 degrees up from horizontal at an operating speed, the light may be pointed too high to comply with the vertical sector requirement. Care must therefore be taken to mount the navigation lights with respect to what is horizontal at operating trim rather than what is horizontal at the dock.

Barges on inland waterways do not normally heel at all, and if unmanned they typically carry battery-powered navigation lights. So that unwieldy battery packs are not needed this special class of vessel may use navigation lights with special, very efficient lenses that concentrate light in a narrow beam around the horizon.


INTERNATIONAL

INLAND

11. Intensity of non-electric lights

Non-electric lights shall so far as practicable comply with the minimum intensities, as specified in the Table given in Section 8 of this Annex.

§ 84.21 Intensity of non-electric lights

Non-electric lights shall so far as practicable comply with the minimum intensities, as specified in the Table given in § 84.15.

 

Lanterns using oil, kerosene, and such for their light source do not have to meet the intensity requirements of Annex I if not "practicable." Operators must adjust the flame to an optimal level, however, and keep the lenses clean.


INTERNATIONAL

INLAND

12. Maneuvering light

Notwithstanding the provisions of paragraph 2(f) of this Annex 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 meters vertically above the forward masthead light, provided that it shall be carried not less than 2 meters vertically above or below the after masthead light. On a vessel where only one masthead light is carried the maneuvering light, if fitted, shall be carried where it can best be seen, not less than 2 meters vertically apart from the masthead light.

§ 84.23 Maneuvering light

Notwithstanding the provisions of § 84.03(f), the maneuvering light described in Rule 34(b) shall be placed approximately in the same fore and aft vertical plane as the masthead light or lights and, where practicable, at a minimum height of one-half meter vertically above the forward masthead light, provided that it shall be carried not less than one-half meter vertically above or below the after masthead light. On a vessel where only one masthead light is carried the maneuvering light, if fitted, shall be carried where it can best be seen, not less than one-half meter vertically apart from the masthead light.

 

The maneuvering light is optional and is used to supplement the maneuvering and warning whistle signals of Rule 34. The maneuvering light is an all-round white light (yellow is optional under Inland Rules) having a minimum range of five miles (International) or two miles (Inland). See Rule 34(b)(iii).


INTERNATIONAL

INLAND

13. High Speed Craft

The masthead light of high speed craft with a length to breadth ratio of less than 3.0 may be placed at a height related to the breadth of the craft lower than that prescribed in paragraph 2(a)(i) of this annex, provided that the base angle of the isosceles trangles formed by the sidelights and masthead light, when seen in end elevation, is not less than 27 degrees.

§ 84.27 High-speed craft.

The masthead light of high speed-craft with a length to breadth ratio of less than 3.0 may be placed at a height related to the breadth lower than that prescribed in Sec. 84.03(a)(1), provided that the base angle of the isosceles trangle formed by the sidelights and masthead light when seen in end elevation is not less than 27 degrees as determined by the formula in paragraph (b) of this section.

(b) The minimum height of masthead light above sidelights is to be determined by the following formula: Tan 27 degrees = X/Y; where Y is the horizontal distance between the sidelights and X is the height of the forward masthead light.

 

Annex I (section 2 / § 84.03) specifies that for vessels wider than six meters, the masthead light shall be mounted at a height above the hull not less than the beam of the vessel (although maximum limits are given). For certain very wide high speed craft, such as hovercraft, hydrofoils, and some catamarans, this requirement has proved to be inappropriate when compared to vessels with more conventional proportions and performance. This section (13. / § 84.27) sets out a more suitable requirement.



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