Rule 34: manoeuvring and warning signals.

What does COLREGs Rule 34 say?

Rule 34(a) gives the whistle signals for a manoeuvre, and 34(b) the light signals that may go with them. Rule 34(c) gives the overtaking signals in a narrow channel or fairway, 34(d) the doubt signal, 34(e) the signal at a bend or obstruction, and 34(f) says only one whistle is used when a vessel has whistles more than 100 metres apart.

What are the manoeuvring signals in Rule 34(a)?

When vessels are in sight of one another, a power-driven vessel underway that manoeuvres 'as authorized or required by these Rules' indicates it on her whistle:

One short blast: 'I am altering my course to starboard'.

Two short blasts: 'I am altering my course to port'.

Three short blasts: 'I am operating astern propulsion'.

Who has to give them?

A power-driven vessel underway, with the vessels in sight of one another — and the rule says 'shall'. A vessel under sail with no engine in use is a sailing vessel (Rule 3(c)), so 34(a) does not bind her; a sailing yacht with her propelling machinery in use — motor-sailing — is a power-driven vessel (Rule 3(b)), and it does.

The signals are for vessels in sight. Vessels are in sight only when one can be observed visually from the other (Rule 3(k)), so an alteration for a radar contact you cannot see in fog is not signalled under 34(a). The Rule 35 signals apply instead.

Does three short blasts mean the vessel is moving astern?

No — it means 'I am operating astern propulsion'. As we read it, the signal reports what the engines are doing: a vessel that has just put her engines astern may still be moving ahead through the water.

When do you sound a manoeuvring signal?

The rule's words are in the present tense — 'I am altering'. In practice, sound it as you make the manoeuvre: it reports an action under way, not an offer or a request. That is the difference from the overtaking signals in 34(c), which say 'I intend'.

What is the light signal in Rule 34(b)?

Any vessel may supplement the 34(a) whistle signals with light signals, repeated as appropriate while the manoeuvre is carried out: one flash for starboard, two for port, three for astern propulsion (34(b)(i)).

Each flash lasts about one second, the interval between flashes is about one second, and the interval between successive signals is not less than 10 seconds (34(b)(ii)). The light, if fitted, is an all-round white light visible at a minimum range of five miles, complying with Annex I (34(b)(iii)).

How do you signal to overtake in a narrow channel?

Rule 34(c) applies when the vessels are in sight of one another in a narrow channel or fairway. The vessel intending to overtake, complying with Rule 9(e)(i), signals on her whistle:

Two prolonged blasts followed by one short blast: 'I intend to overtake you on your starboard side'.

Two prolonged blasts followed by two short blasts: 'I intend to overtake you on your port side'.

The vessel about to be overtaken shows her agreement with one prolonged, one short, one prolonged and one short blast, 'in that order' (34(c)(ii)).

When is the overtaking signal used?

Rule 9(e)(i) says when: in a narrow channel or fairway, where overtaking can take place only if the vessel to be overtaken has to act to permit safe passing. If she agrees, she sounds the 34(c)(ii) signal and takes steps to permit safe passing; if she is in doubt, she may sound the signals in Rule 34(d). Rule 9(e)(ii) adds that this does not relieve the overtaking vessel of her obligation under Rule 13 (Overtaking).

Is there a way to remember which overtaking signal is which?

A memory aid of ours: the short blasts at the end match Rule 34(a). One short blast is starboard there, and two prolonged plus one short is 'on your starboard side' here; two short is port in both.

What does Rule 34(e) require at a bend?

Nearing a bend, or a stretch of channel or fairway where an obstruction may hide other vessels, sound one prolonged blast. Any vessel approaching from the other side that may hear it answers with one prolonged blast.

Rule 9(f) ties this to narrow channels: a vessel nearing such a bend or area must navigate with 'particular alertness and caution' and sound the 34(e) signal. Unlike 34(a), (c) and (d), the bend signal is not limited to vessels in sight of one another — its whole point is that they are not.

Isn't one prolonged blast also a fog signal?

Yes. Under Rule 35(a), one prolonged blast at intervals of not more than two minutes is a power-driven vessel making way in restricted visibility. In practice the circumstances tell them apart: the bend signal is sounded on nearing a bend or obstruction and answered by vessels beyond it.

What is the doubt signal in Rule 34(d)?

In sight of one another and closing, if you cannot make out what the other vessel is doing, or doubt she is doing enough to avoid collision, sound at least five short and rapid blasts on the whistle — 'immediately', the rule says. At least five short and rapid flashes may back it up.

It is for any vessel in that position, not only a power-driven one. Rule 9 points to it twice: 9(d), for a vessel that can safely navigate only within a narrow channel or fairway and is in doubt about a crossing vessel's intention, and 9(e)(i), for a vessel in doubt about being overtaken.

Does sounding the doubt signal change who keeps clear?

As we read it, no. The signal tells the other vessel you are in doubt; it does not change anyone's duties under the steering and sailing rules (Part B). Who keeps out of the way is still set by Rules 12 to 18, and the action you take is still governed by Rule 8.

What does Rule 34(f) say about two whistles?

Fit whistles more than 100 metres apart and the rule allows just one of them for manoeuvring and warning signals.

Annex III fills in the rest. Whistles more than 100 metres apart are arranged so they are not sounded simultaneously (1(f)). A combined whistle system — whistles not more than 100 metres apart, sounded together — counts as a single whistle (1(g)). In our view the point is clarity: two whistles far apart reach a listener at different moments, which can blur the count of blasts.

How might Rule 34 come up in an MCA oral?

It may come up as a signal to identify, or as the follow-up to a steering scenario. Examples of the kind of question to be ready for:

“You're on a power-driven vessel in sight of another and alter course to port. What do you sound?”

“What does three short blasts mean?”

“You want to overtake a vessel in a narrow channel on her port side, and she will have to move over. What do you sound, and what do you expect to hear back?”

“You hear five short and rapid blasts. What does it mean?”

“You're approaching a blind bend in a river. What do you sound?”

“In fog you alter to starboard for a radar contact you can't see. Do you sound one short blast?”

Where do candidates go wrong on Rule 34?

The common slips: saying 'going astern' for 'operating astern propulsion'; giving the 34(a) signals as a sailing vessel under sail; sounding manoeuvring signals in fog to a vessel that is not in sight; mixing up the starboard and port overtaking signals; getting the order of the agreement signal wrong; forgetting that the bend signal is answered; and saying 'five short blasts' when the rule says 'at least five'.