Rule 27 — Not under command and RAM
Two reds for a vessel that cannot manoeuvre; red, white, red for one whose work restricts her. Then the variations for towing, dredging, diving and mineclearance, the small-vessel exemption, and how it all comes up in an MCA oral.
It sets the lights and shapes for two kinds of vessel that cannot keep out of the way of others: a vessel not under command (27(a)) and a vessel restricted in her ability to manoeuvre (27(b)), with 27(c) to (f) adapting the second for towing, dredging or underwater operations, diving and mineclearance. Rule 27(g) exempts small vessels; 27(h) says none of these is a distress signal.
Rule 27(a): two all-round red lights in a vertical line, and by day 'two balls or similar shapes' in a vertical line, both where they can best be seen. When she is making way through the water she adds sidelights and a sternlight.
Rule 27(a) lists no masthead light. And the trigger for the sidelights is making way, not being underway: Rule 3(i) defines underway as not at anchor, made fast to the shore or aground, so a vessel not under command with no way through the water (lying stopped, or carried by the tide) is underway but not making way, and shows only the two reds.
Rule 3(f): a vessel which 'through some exceptional circumstance' is unable to manoeuvre as required by the rules, and is therefore unable to keep out of the way of another vessel. In practice, a main engine or steering gear failure is the typical case.
As we read it, a vessel that has merely stopped her engines, and could manoeuvre if she had to, is not 'unable to manoeuvre' and does not qualify.
Rule 27(a) makes no provision for a vessel at anchor — unlike 27(b)(iv), which tells a vessel restricted in her ability to manoeuvre what to add at anchor. As we read it, once a disabled vessel is anchored she is a vessel at anchor, and shows the anchor light or lights, or ball, of Rule 30 rather than the not-under-command signal. Keeping the two reds on as well would be read as aground: two all-round reds with anchor lights is the Rule 30(d) signal.
Rule 27(b), for every such vessel except one engaged in mineclearance: three all-round lights in a vertical line where they can best be seen, the highest and lowest red and the middle one white. By day, three shapes in a vertical line: a ball, a diamond, a ball.
When making way through the water she adds a masthead light or lights, sidelights and a sternlight (27(b)(iii)). At anchor she adds the anchor light, lights or shape of Rule 30 to her red-white-red or ball-diamond-ball (27(b)(iv)).
Rule 3(g): a vessel which 'from the nature of her work' is restricted in her ability to manoeuvre as required by the rules, and so cannot keep out of the way of another vessel — her work, not an exceptional circumstance. The list 'shall include but not be limited to' vessels engaged in laying, servicing or picking up a navigation mark, submarine cable or pipeline; dredging, surveying or underwater operations; replenishment or transferring persons, provisions or cargo while underway; launching or recovery of aircraft; mineclearance; and certain towing operations.
Not every tow counts — only one that severely restricts the towing vessel and her tow in their ability to deviate from their course. A power-driven vessel in that position shows the lights or shapes of Rule 24(a) and, in addition, the red-white-red lights and ball-diamond-ball shapes of 27(b)(i) and (ii).
Rule 24(a) includes two masthead lights in a vertical line (three when the tow exceeds 200 metres), sidelights, a sternlight with a yellow towing light above it, and a diamond shape when the tow exceeds 200 metres.
A vessel engaged in dredging or underwater operations, when restricted in her ability to manoeuvre, shows the 27(b) red-white-red lights and ball-diamond-ball shapes, and when making way through the water the masthead light or lights, sidelights and sternlight. When an obstruction exists she adds two more signals:
(i) two all-round red lights or two balls in a vertical line, on the side where the obstruction exists; and
(ii) two all-round green lights or two diamonds in a vertical line, on 'the side on which another vessel may pass'.
So you pass on the side of the greens by night and the diamonds by day. Annex I, section 4(b), sets these signals as far to the side of the red-white-red or ball-diamond-ball as is practical, and never less than two metres, with the upper one no higher than the lowest of those three. At anchor, Rule 27(d)(iii) has her show these lights or shapes instead of the Rule 30 anchor lights or ball.
When the size of a vessel engaged in diving operations makes it impracticable to show all the 27(d) lights and shapes, she shows instead three all-round lights in a vertical line where they can best be seen — red, white, red — and 'a rigid replica of the International Code flag “A”' not less than one metre in height, with measures taken to ensure it can be seen all round.
On top of her normal signals — the Rule 23 lights of a power-driven vessel, or the Rule 30 anchor lights or shape, whichever fits — she adds three green all-round lights by night or three balls by day: one near the foremast head and one at each end of the fore yard. The message is a warning to keep off: it is dangerous for another vessel to come within 1,000 metres of her.
She does not show red-white-red — 27(b) excludes mineclearance — though Rule 3(g)(v) still counts her as restricted in her ability to manoeuvre. In practice, three balls at the foremast head and the yard ends form a triangle, unlike the vertical line of three balls of a vessel aground (Rule 30(d)).
Rule 27(g): below 12 metres in length, a vessel need not show the Rule 27 lights and shapes. The one exception is a vessel engaged in diving operations, so a small dive boat is not exempt.
No. Rule 27(h) says the Rule 27 signals are 'not signals of vessels in distress and requiring assistance'; those are in Annex IV. A vessel not under command is telling others she cannot keep out of their way, not asking for help. If she is in distress and needs assistance, she uses an Annex IV signal, such as 'MAYDAY' by radiotelephony. Annex IV, section 2, prohibits those signals for any other purpose, so a vessel that simply needs a tow does not use them.
Rule 18, except where Rules 9, 10 and 13 otherwise require: a power-driven vessel underway and a sailing vessel underway keep out of the way of both a vessel not under command and a vessel restricted in her ability to manoeuvre, and a vessel engaged in fishing when underway does so 'so far as possible'. Those duties are for vessels in sight of one another (Rule 11); vessels not in sight of one another in or near restricted visibility come under Rule 19.
Rule 35(c): one prolonged blast followed by two short blasts, at intervals of not more than two minutes — for a vessel not under command and a vessel restricted in her ability to manoeuvre alike. Under Rule 35(d), a vessel restricted in her ability to manoeuvre carrying out her work at anchor sounds that same signal instead of the anchor signals of Rule 35(g).
It may come up as a lights and shapes question, then a conduct question. Examples of the kind of question to be ready for:
“At night, ahead of you, two all-round red lights in a vertical line and a green sidelight. What is she, what is she doing, and what do you do?”
“By day you see a ball, a diamond and a ball in a vertical line. What is she, and who keeps out of whose way?”
“A dredger shows two greens in a vertical line on one side and two reds on the other. Which side do you pass?”
“Why does a small dive boat show a rigid flag ‘A’ rather than the full dredging signals?”
The common slips: giving a vessel not under command a masthead light; tying her sidelights to being underway rather than making way; passing a dredger on the side of the reds; forgetting that 27(g) does not exempt small diving vessels; mixing up the three mineclearance balls with the three balls in a vertical line of a vessel aground; and calling the not-under-command lights a distress signal.
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