Rule 27 — Not Under Command and Restricted in Ability to Maneuver: Lights and Shapes

What the rule requires

The two light pictures at the head of this rule are the ones that appear on the exam, and the older deckplate rhymes are still the fastest way in: red over red, the engine's dead for not under command, red, white, red — I can't turn my head for restricted in ability to maneuver. Both are sound as far as colour and order go. Neither tells you what else is burning, and that is where questions are won.

Not under command. Two all-round red lights in a vertical line where they can best be seen; two balls or similar shapes in a vertical line by day; and when making way through the water, in addition to those lights, sidelights and a sternlight COLREGs Rule 27(a). Read the list again for what is missing. A masthead light appears nowhere in paragraph (a). A NUC vessel driven through the water by residual headway shows two reds, sidelights and a sternlight, and nothing above them.

Restricted in her ability to maneuver, mine clearance excepted, shows three all-round lights in a vertical line, highest and lowest red and the middle white; by day three shapes in a vertical line, highest and lowest balls with a diamond between them; when making way through the water, a masthead light or lights, sidelights and a sternlight in addition to the red-white-red; and when at anchor, the anchor light, lights or shapes of Rule 30 in addition to the red-white-red and the ball-diamond-ball COLREGs Rule 27(b).

So the masthead light is the discriminator between the two classes when both are making way, and the middle light is the discriminator when neither is.

At 0230 you sight two all-round red lights in a vertical line, sidelights and a sternlight, no masthead light. What are you looking at, and is she moving?

A vessel not under command, making way through the water. The two all-round reds identify her under Rule 27(a); the sidelights and sternlight are added only when making way. The absence of a masthead light is correct and expected — paragraph (a) never prescribes one. Had the picture been red-white-red with a masthead light, she would be restricted in her ability to maneuver and making way.

Dredging and underwater operations

A vessel engaged in dredging or underwater operations, when restricted in her ability to maneuver, shows the full RAM outfit — red-white-red, ball-diamond-ball, and the masthead light, sidelights and sternlight when making way — and in addition, when an obstruction exists, two all-round red lights or two balls in a vertical line to indicate the side on which the obstruction exists, and two all-round green lights or two diamonds in a vertical line to indicate the side on which another vessel may pass COLREGs Rule 27(d).

Green is the side you pass. Red is the gear, the spoil barge, the pipeline, the thing that will stop your vessel.

When at anchor, she shows the lights or shapes of paragraph (d) instead of the anchor lights of Rule 30 — not in addition to them. That substitution is the trap in the paragraph, and it is worth more than the rest of (d) put together, because it means an anchored dredge shows no anchor light and a candidate looking for one will conclude she is underway.

Small vessels engaged in diving operations

Where the size of a vessel engaged in diving operations makes it impracticable to show everything paragraph (d) prescribes, she shows instead three all-round lights in a vertical line, highest and lowest red and the middle white, and a rigid replica of the International Code flag "A" not less than 1 meter in height, with measures taken to ensure its all-round visibility COLREGs Rule 27(e).

Two exact values live here: the 1-metre minimum, and the requirement that the replica be rigid. A flag "A" flying soft on a halyard does not satisfy the rule.

Towing that severely restricts the tow

A power-driven vessel engaged in a towing operation such as severely restricts the towing vessel and her tow in their ability to deviate from their course shows the RAM lights or shapes of (b)(i) and (b)(ii) in addition to the towing lights or shapes of Rule 24 COLREGs Rule 27(c). The trigger is the severe restriction on deviating from course, not the mere fact of towing.

Mine clearance

In addition to the lights prescribed for a power-driven vessel in Rule 23, or the anchor lights or shape of Rule 30 as appropriate, a vessel engaged in mine clearance operations shows three all-round green lights or three balls — one near the foremast head and one at each end of the fore yard. These indicate that it is dangerous for another vessel to approach within 1000 meters COLREGs Rule 27(f). She is the one class of RAM vessel expressly carved out of paragraph (b), so she does not show red-white-red at all.

The exemption, and what it does not cover

A vessel of less than 12 meters in length is not required to exhibit the lights or shapes of this rule, except when engaged in diving operations COLREGs Rule 27(g). The diving exception is what gets tested; the length threshold on its own rarely is.

And the signals of Rule 27 are not signals of vessels in distress requiring assistance — those are in Annex IV COLREGs Rule 27(h), which the Inland text carries as 33 CFR part 87 33 CFR §83.27.

Dredge pipelines

The Inland text specifies lights for dredge pipelines that are floating or supported on trestles, displayed at night and in restricted visibility: one row of yellow lights flashing 50 to 70 times per minute, visible all round the horizon, visible for at least 2 miles, mounted not less than 1 and not more than 3.5 meters above the water, approximately equally spaced, and not more than 10 meters apart where the pipeline crosses a navigable channel. Two red lights go at each end of the pipeline, visible all round and for at least 2 miles, 1 meter apart vertically with the lower light at the same height as the flashing yellow lights.

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Telling it apart

The single criterion that separates these light pictures is the middle element — whether there is one, and what colour it is. Everything else follows.

• Not under command — no middle element. Two all-round reds; two balls by day. Most often misfiled: candidates add a masthead light when told she is making way. She never shows one under this rule.
• Restricted in her ability to maneuver — a white light between two reds; a diamond between two balls. Most often misfiled: a vessel at anchor. She keeps her red-white-red and adds the Rule 30 anchor light.
• Dredge or vessel in underwater operations with an obstruction — red-white-red plus a two-light or two-shape pair on each beam: two reds or two balls on the obstructed side, two greens or two diamonds on the side you may pass. Most often misfiled: at anchor she shows this picture instead of Rule 30, so there is no anchor light to look for.
• Small vessel in diving operations — red-white-red at night, and by day a rigid flag "A" replica at least 1 metre high rather than ball-diamond-ball.
• Mine clearance vessel — three greens or three balls, spread near the foremast head and at the ends of the fore yard, on top of ordinary Rule 23 or Rule 30 lights. No red-white-red.

Underway, making way, at anchor

Rule 27 draws its distinctions on making way through the water, not on being underway. A NUC vessel lying dead in the water with no way on shows two reds and nothing else. Put way on her and the sidelights and sternlight come on. A RAM vessel not making way shows red-white-red alone; making way, she adds masthead light or lights, sidelights and sternlight; at anchor, red-white-red plus the anchor light.

Working a question

You are outbound at 0300 in a 19-metre passenger vessel in a dredged channel. Broad on the port bow you sight three all-round lights in a vertical line, red over white over red. Below and outboard of them, to the left of the display as you see it, two all-round red lights in a vertical line; to the right, two all-round green lights in a vertical line. No masthead light, no sidelights, no sternlight, no anchor light.

1. Red over white over red identifies a vessel restricted in her ability to maneuver under paragraph (b)(i).
2. The additional pairs — two reds and two greens on opposite sides — are prescribed only by paragraph (d). She is engaged in dredging or underwater operations with an obstruction alongside.
3. No masthead light, sidelights or sternlight means she is not making way, since (b)(iii) requires all three of those when she is.
4. No anchor light does not put her underway. Paragraph (d)(iii) substitutes this display for the Rule 30 anchor lights, so an anchored dredge shows exactly what you are seeing.
5. The two green lights mark the side on which another vessel may pass. From your position, that is the side to your right as you look at her display. Alter to pass on the green side and stay well clear of the reds, which mark the obstruction.

The decision is made at step 5, but it is unavailable until step 2 tells you which rule governs the extra lights. A candidate who stops at "RAM, keep clear" has no basis for choosing a side.

Where candidates lose the point

Answering "masthead light, sidelights and sternlight" for a NUC vessel making way. The option is attractive because it is the correct answer for a RAM vessel making way, and the two paragraphs sit next to each other. Paragraph (a)(iii) lists sidelights and a sternlight only.

Swapping the day shapes. Two balls is NUC; ball-diamond-ball is RAM. The diamond is the white light in the night picture and it sits in the same place — middle of three.

Hunting for an anchor light on a dredge. Under (d)(iii) the dredging display replaces Rule 30, and a candidate who reasons "no anchor light, therefore underway" will pick the wrong action for a vessel that is not going anywhere.

Reading the two red lights as the clear side. Red marks the obstruction. Passing there puts you into the gear.

Assuming every vessel under 12 metres is off the hook. Paragraph (g) exempts vessels of less than 12 metres from this rule, then names one exception: diving operations. A 7-metre dive boat is required to display.

Choosing "the vessel is in distress and requires assistance." Two all-round reds read as an emergency, and the vessel may well be in trouble, but paragraph (h) settles it: these are not distress signals. Distress signals are in Annex IV.

Treating any towing vessel as a RAM vessel. The trigger in (c) is a towing operation that severely restricts the towing vessel and her tow in their ability to deviate from their course, and even then the RAM lights are additional to the Rule 24 towing lights.

Hedging on the International/Inland label. 33 CFR §83.27 and COLREGs Rule 27 agree throughout on NUC and RAM lights and shapes. A question tagged "(Both International & Inland)" on this topic has no divergence trap in it.

Check yourself

You are on watch at night and sight, ahead, three all-round lights in a vertical line — red, white, red — with a masthead light, sidelights and a sternlight. What is her status?

Restricted in her ability to maneuver and making way through the water. Paragraph (b)(iii) adds the masthead light or lights, sidelights and sternlight to the red-white-red only when she is making way. Had she been at anchor, the red-white-red would have been shown with the Rule 30 anchor light and no masthead light.

Your engine room reports total loss of propulsion. You still carry two knots of headway. What must you display at night?

Two all-round red lights in a vertical line, plus sidelights and a sternlight because you are making way. No masthead light — Rule 27(a) does not prescribe one at any time. By day, two balls in a vertical line.

A 40-metre dredge at anchor with an obstruction on her starboard side. What lights, and what does she omit?

Red over white over red; two all-round red lights in a vertical line on the starboard side to mark the obstruction; two all-round green lights in a vertical line on the port side to show where you may pass. She omits the Rule 30 anchor light — paragraph (d)(iii) has her show the dredging lights instead of it. She also shows no masthead light, sidelights or sternlight, as she is not making way.

An 8-metre vessel is tending a diver. Does the under-12-metre exemption relieve her of Rule 27 lights and shapes?

No. Paragraph (g) exempts vessels of less than 12 metres in length from this rule except when engaged in diving operations. Where her size makes the full paragraph (d) display impracticable, she shows red-white-red at night and, by day, a rigid replica of the International Code flag "A" not less than 1 metre in height, made visible all round.

You sight a vessel showing ordinary power-driven vessel lights plus three all-round green lights — one near the foremast head, one at each end of the fore yard. What is she, and how close may you go?

A vessel engaged in mine clearance operations. Her display indicates that it is dangerous to approach within 1000 metres. She is excepted from paragraph (b), which is why there is no red-white-red on her.

By day you see a vessel displaying two black balls in a vertical line. A crewmember says she is signalling distress. Correct him.

The two balls identify a vessel not under command under Rule 27(a). Paragraph (h) states that the signals of this rule are not signals of vessels in distress requiring assistance; those are in Annex IV, carried in the Inland regulations as 33 CFR part 87. She may be disabled, and she is to be kept clear of, but she has not called for assistance by showing this shape.

A tug with a barge on a long hawser, where the tow severely restricts her ability to deviate from her course. What does she add to her towing lights?

The RAM lights and shapes of (b)(i) and (b)(ii) — red over white over red at night, ball-diamond-ball by day — in addition to the lights or shapes prescribed by Rule 24. The addition is triggered by the severe restriction on deviating from course, not by the towing operation as such.