22.34 Manoeuvring and warning signals

(1) When vessels are in sight of one another, a power-driven vessel underway, manoeuvring as authorised or required by this Part, must indicate that manoeuvre by the following signals on its whistle—

(a) one short blast to mean “I am altering my course to starboard”:

(b) two short blasts to mean “I am altering my course to port”:

(c) three short blast to mean “I am operating astern propulsion”.

(2) Any vessel may supplement the whistle signals prescribed in rule 22.34(1) with the following light signals, repeated as appropriate, whilst the manoeuvre is being carried out—

(a) one flash to mean “I am altering my course to starboard”:

(b) two flashes to mean “ I am altering my course to port”:

(c) three flashes to mean “I am operating astern propulsion”.

The duration of each flash must be about one second, the interval between successive flashes must be about one second, and the interval between successive signals must not be less than 10 seconds.

The light used for this signal must, if fitted, be an all-round white light. It must be visible for a minimum distance of 5 miles and comply with the provisions of Appendix 1.12 of this Part.

(3) When in sight of one another in a narrow channel or fairway—

(a) a vessel intending to overtake another must indicate its intention in compliance with rule 22.9 (narrow channels) by sounding one of the following sound signals on its whistle:

two prolonged blasts followed by one short blast to mean “I intend to overtake you on your starboard side”;

OR

two prolonged blasts followed by two short blasts to mean “I intend to overtake you on your port side”;

(b) the vessel about to be overtaken when acting in compliance with rule 22.9 (narrow channels) must indicate its agreement by sounding the following signal on its whistle:

one prolonged, one short, one prolonged and one short blast, in that order.

(4) When vessels in sight of one another are approaching each other and for any reason either fails to understand the intentions or actions of the other, OR is in any doubt whether sufficient action is being taken by the other to avoid collision, the vessel in doubt must immediately indicate such doubt by sounding the following signal on its whistle—

at least five short and rapid blasts.

This signal may be supplemented by a light signal of at least 5 short and rapid flashes.

(5) A vessel nearing a bend or an area of a channel or fairway where other vessels may be obscured by an intervening obstruction must sound one prolonged blast.

Such signal must be answered with a prolonged blast by any approaching vessel that may be within hearing around the bend or behind the intervening obstruction.

(6) If whistles are fitted on a vessel at a distance apart of more than 100 metres, one whistle only must be used for giving manoeuvring and warning signals.