Boats.com - Rules and Regulations: Navigational Rules

Where it is impractical for a seaplane to exhibit lights and shapes of the characteristics or in the positions prescribed in the Rules of this Part, she shall exhibit lights and shapes as closely similar in characteristics and position as is possible.

Rule 31
When on the water, a seaplane (or amphibian) is a "vessel" in terms of the Navigation Rules. "In this part" refers to Rules 20 through 30.

(a) The word "whistle" means any sound-signalling appliance capable of producing the prescribed blasts and which complies with the specifications in Annex III to these Regulations.
(b) The term "short blast" means a blast of about one second's duration.
(c) The term "prolonged blast" means a blast of from four to six seconds' duration.

Rule 32
This Rule broadens the term "whistle" to include sound-producing devices that are more likely to be found on smaller vessels - if it can make a sound that meets the requirements of the Rules and Annex III, it's a whistle.

Note that there are only two kinds of whistle blasts - short and prolonged; the term "long blast" does not appear in either set of the Navigation Rules.

(a) A vessel of 12 meters or more in length shall be provided with a whistle and a bell, and a vessel of 100 meters or more in length shall, in addition, be provided with a gong, the tone and sound of which cannot be confused with that of the bell. The whistle, bell and gong shall comply with the specifications in Annex III to these Regulations. The bell or gong or both may be replaced by other equipment having the same respective sound characteristics, provided that manual sounding of the prescribed signals shall always be possible.
(b) a vessel of less than 12 meters in length shall not be obliged to carry the sound signalling appliances prescribed in paragraph (a) of this Rule, but if she does not, she shall be provided with some other means of making an efficient sound signal.

Rule 33
There are only three types of sound-signal equipment mentioned in the Rules - whistle, bell, and gong, with the latter only required on vessels 100 meters or more in length. Even if the sound of a bell or gong can be created by other means (electronic), manual sounding must always be possible. There is no use of the term "fog horn" in the Rules; "fog" signals are sounded on the same whistle as used for other purposes.

Automatically timed fog signals are widely used, but caution is advised lest your signals get in synchronization with those of another vessel and you don't hear that vessel.

(a) When vessels are in sight of one another, a power-driven vessel underway, when maneuvering as authorized or required by these Rules, shall indicate that maneuver by the following signals on her whistle:

one short blast to mean "I am altering my course to starboard";
two short blasts to mean "I am altering my course to port";
three short blasts to mean "I am operating astern propulsion."

(b) Any vessel may supplement the whistle signals prescribed in paragraph (a) of this Rule by light signals, repeated as appropriate, while the maneuver is being carried out:

(i) these light signals shall have the following significance:

one flash to mean "I am altering my course to starboard";
two flashes to mean "I am altering my course to port";
three flashes to mean "I am operating astern propulsion."

(ii) the duration of each flash shall be about one second, the interval between flashes shall be about one second, and the interval between successive signals shall be no less than ten seconds;
(iii) the light used for this signal shall, if fitted, be an all-round white light, visible at a minimum range of 5 miles and shall comply with the provisions of Annex I to these regulations.

(i) a vessel intending to overtake another shall, in compliance with Rule 9(e)(i), indicate her intention by the following signals on her whistle:

two prolonged blasts followed by one short blast to mean "I intend to overtake you on your starboard side";
two prolonged blasts followed by two short blasts to mean "I intend to over-take you on your port side."

(ii) the vessel about to be overtaken when acting in accordance with Rule 9(e)(i) shall indicate her agreement by the following signal on her whistle: One prolonged, one short, one prolonged and one short blast, in that order.

(d) When vessels in sight of one another are approaching each other and, from any cause, either vessel fails to understand the intentions or actions of the other, or is in doubt whether sufficient action is being taken by the other to avoid collision, the vessel in doubt shall immediately indicate such doubt by giving at least five short and rapid blasts on the whistle. Such signal may be supplemented by a light signal of at least five short and rapid flashes.
(e) A vessel nearing a bend or an area of a channel or fairway where other vessels may be obscured by an intervening obstruction shall sound one prolonged blast. Such signal shall be answered with a prolonged blast by any approaching vessel that may be within hearing around the bend or behind the intervening obstruction.
(f) If whistles are fitted on a vessel at a distance apart of more than 100 meters, one whistle only shall be used for giving maneuvering and warning signals.

Rule 34
This Rule contains the most significant variations between the International and Inland Rules - and these differences must be clearly understood.

The International Rules whistle signals for power-driven vessels underway in sight of each other are signals of actions being taken - they are required between two such vessels in sight of one another, and do not require a reply. The Inland Rules whistle signals for power-driven vessels are signals of intent - they are required in sight of one another and are meeting or crossing at a distance within half a mile of each other. These signals require a reply.
The meanings of the one and two short-blast signals are different in the two sets of Rules. Be sure of which set governs the waters you are on at all times so that you may properly sound your signals and interpret the signals of other vessels. These signals are not to be used in conditions of restricted visibility. Fortunately, the very important signal of doubt or danger - five or more short and rapid blasts - is the same on all waters.

The three-blast sound signal in both sets of Rules has the same meaning. "Operating astern propulsion" means only that; it does not necessarily mean that the vessel has stopped or is making sternway. The deciding factor is the operation of the propulsion machinery, not the movement of the vessel.

In both sets of Rules, the one, two, three, and five or more short blast signals may be supplemented by light signals with the corresponding number of one-second flashes at one-second intervals. Note that the light signals may not be substituted for the sound signals.

The International Rules require that this light be white; the light signals need not be synchronized with the whistle blasts, and may be repeated after an interval of ten seconds. The Inland Rules allow either white or yellow; the light flashes must be synchronized with the whistle blasts and cannot be repeated separately. The required visibility ranges are different for the two sets of Rules.

Note that Rule 34 is applicable only to power-driven vessels - vessels under sail are not required to sound maneuvering signals (unless, of course, they are also using mechanical propulsion, in which case they are not sailing vessels).

In waters governed by the International Rules, a power-driven vessel may sound a whistle signal to a sailing vessel to indicate action being taken. However, in Inland Rules waters, a power-driven vessel should not sound whistle signals of intent to a sailing vessel, as that vessel cannot reply.

In overtaking situations, the signals of the International Rule are applicable only if the encounter occurs in a narrow channel and the overtaken vessel must maneuver to allow safe passage of the other. In the Inland Rules, the signals are required in all circumstances if the vessels will come within a half-mile of each other.

The signals of the two sets of Rules are quite different, with the International being more complex.

In or near an area of restricted visibility, whether by day or night, the signals prescribed in this Rule shall be used as follows.

(a) A power-driven vessel making way through the water shall sound at intervals of not more than 2 minutes one prolonged blast.
(b) A power-driven vessel underway, but stopped and making no way through the water, shall sound at intervals of not more than 2 minutes two prolonged blasts in succession with an interval of about 2 seconds between them.
(c) A vessel not under command, a vessel restricted in her ability to maneuver, a vessel constrained by her draft, a sailing vessel, a vessel engaged in fishing and a vessel engaged in towing or pushing another vessel shall, instead of the signals prescribed in paragraphs (a) or (b) of this Rule, sound at intervals of not more than 2 minutes three blasts in succession, namely one prolonged followed by two short blasts.
(d) A vessel engaged in fishing, when at anchor, and a vessel restricted in her ability to maneuver when carrying out her work at anchor, shall instead of the signals prescribed in paragraph (g) of this Rule sound the signal prescribed in paragraph (c) of this Rule.
(e) A vessel towed or, if more than one vessel is towed, the last vessel of the tow, if manned, shall at intervals of not more than 2 minutes sound four blasts in succession, namely one prolonged followed by three short blasts. When practicable, this signal shall be made immediately after the signal made by the towing vessel.
(f) When a pushing vessel and a vessel being pushed ahead are rigidly connected in a composite unit they shall be regarded as a power-driven vessel and shall give the signals prescribed in paragraphs (a) or (b) of this Rule.
(g) A vessel at anchor shall, at intervals of not more than one minute, ring the bell rapidly for about five seconds. In a vessel of 100 meters or more in length the bell shall be sounded in the forepart of the vessel and immediately after the ringing of the bell the gong shall be sounded rapidly for about five seconds in the after part of the vessel. A vessel at anchor may, in addition, sound three blasts in succession, namely one short, one prolonged and one short blast to give warning of her position and of the possibility of collision to an approaching vessel.
(h) A vessel aground shall give the bell signal and, if required, the gong signal prescribed in paragraph (g) of this Rule, and shall, in addition, give three separate and distinct strokes on the bell immediately before and after the rapid ringing of the bell. A vessel aground may, in addition, sound an appropriate whistle signal.
(i) A vessel of less than 12 meters in length shall not be obliged to give the above- mentioned signals but, if she does not, shall make some other efficient sound signal at intervals of not more than 2 minutes.
(j) A pilot vessel when engaged on pilotage duty may, in addition to the signals prescribed in paragraphs (a), (b) or (g) of this Rule, sound an identity signal consisting of four short blasts.

Rule 35
International Rule 35(f) and Inland Rule 35(e) refer to a "composite unit" of a rigidly connected pushing vessel and vessel being pushed. This is a rare situation, as the normal means of connection of wires and winches does not meet this definition. See also Rule 24(b).

If necessary to attract the attention of another vessel, any vessel may make light or sound signals that cannot be mistaken for any signal authorized elsewhere in these Rules, or may direct the beam of her searchlight in the direction of the danger, in such a way as not to embarrass any vessel. Any light to attract the attention of another vessel shall be such that it cannot be mistaken for any aid to navigation. For the purpose of this Rule,the use of high-intensity intermittent or revolving lights, such as strobe lights, shall be avoided.

Rule 36
Note carefully that a signal "to attract the attention of another vessel" is not a distress signal. It is often used by fishing vessels with nets out. A searchlight should be shown only in the direction of the danger; it should never be directed toward the other vessel, lest it blind the helmsman.

The International Rule specifically eliminates the use of strobe lights for the purpose of attracting attention. The Inland Rule does not have this prohibition, but it should be noted that such a light is listed as a distress signal in waters subject to these Rules.

When a vessel is in distress and requires assistance she shall use or exhibit the signals described in annex IV to these Regulations.

Rule 37
Because the primary intent of the Navigation Rules is to prevent collisions, the details of distress signals are not included in the basic Rules - only a reference to Annex IV, where they may be found.

International Navigation Rules