Rule 27: Vessel not under command or restricted in their ability to manoeuvre
- A vessel not under command shall exhibit:
- two all-round red lights in a vertical line where they can best be seen;
- two balls or similar shapes in a vertical line where they can best be seen;
- when making way through the water, in addition to the lights prescribed in this paragraph, sidelights and a stern light.
- A vessel restricted in her ability to manoeuvre, except a vessel engaged in mine-clearance operations, shall exhibit:
- three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white;
- three shapes in a vertical line where they can best be seen. The highest and lowest of these shapes shall be balls and the middle one a diamond;
- when making way through the water, a masthead light or lights, sidelights and a sternlight, in addition to the lights prescribed in sub-paragraph (i);
- when at anchor, in addition to the lights or shapes prescribed in sub-paragraphs (i) and(ii), the light, lights or shape prescribed in Rule 30.
- 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 shall, in addition to the lights or shapes prescribed in Rule 24(a), exhibit the lights or shapes prescribed in sub-paragraphs (b)(i) and (ii) of this Rule.
- A vessel engaged in dredging or underwater operations, when restricted in her ability to manoeuvre, shall exhibit the lights and shapes prescribed in sub-paragraphs (b) (i), (ii) and (iii) of this Rule and shall in addition, when an obstruction exists, exhibit:
- two all-round red lights or two balls in a vertical line to indicate the side on which the obstruction exists;
- two all-round green lights or two diamonds in a vertical line to indicate the side on which another vessel may pass;
- when at anchor, the lights or shapes prescribed in this paragraph instead of the lights or shape prescribed in Rule 30.
- Whenever the size of a vessel engaged in diving operations makes it impracticable to exhibit all lights and shapes prescribed in paragraph (d) of this Rule, the following shall be exhibited:
- three all-round lights in a vertical line where they can best be seen. The highest and lowest of these lights shall be red and the middle light shall be white;
- a rigid replica of the International Code flag “A” not less than 1 metre in height. Measures shall be taken to ensure its all-round visibility.
- A vessel engaged in mine-clearance operations shall in addition to the lights prescribed for a power-driven vessel in Rule 23 or to the lights or shape prescribed for a vessel at anchor in Rule 30 as appropriate, exhibit three all-round green lights or three balls. One of these lights or shapes shall be exhibited near the foremast head and one at each end of the fore yard. These lights or shapes indicate that it is dangerous for another vessel to approach within 1000 metres of the mine clearance vessel.
- Vessels of less than 12 metres in length, except those engaged in diving operations, shall not be required to exhibit the lights and shapes prescribed in this Rule.
- The signals prescribed in this Rule are not signals of vessels in distress and requiring assistance. Such signals are contained in Annex IV to these Regulations.
What this means:
Rule 27: Vessel not under command or restricted in their ability to manoeuvre – Our plain English guide to help you understand & remember this rule.
This rule covers many situations, with multiple vessels potentially becoming either one of these types.
Any vessel may define itself as ‘not under command’ if it cannot manoeuvre due to unforeseen circumstances, such as engine or steerage failure.
Day shape
Two black balls are displayed in a vertical line where they can be seen best.
Lights
Two all-round red lights in a vertical line are shown.
In addition, relevant presence and heading lights (sidelights and a stern light) must be shown if moving through the water.
Switch between day and night to compare it with the equivalent day shapes.
Many vessels are involved in work that may restrict their ability to manoeuvre, for example, buoy, cable & pipe layers, dredgers, survey vessels or engaged in an activity such as a long or difficult tow.
For this reason, Rule 27 is divided into several components as it must cover many different scenarios. However, the critical point to remember is that while there are many different ways of displaying restricted ability to manoeuvre, they are treated the same way regarding the rules.
As with all terms, all are regarded as power-driven vessels until they are involved in the activity.
Day shape
In practical terms, the likelihood of coming across all the vessel types covered by this rule is low, and many are evident without the need to identify the shapes they are showing.
Once engaged in an activity that restricts its ability to manoeuvre, the generic shape shown is a ball over a diamond over a ball.
Generic lights
Once engaged in an activity that restricts its ability to manoeuvre, a vessel shall display an all-round red over white over red lights at night.
It must also show any size-appropriate general lights, such as sidelights, masthead, or anchor lights.
Two all-round red lights in a vertical line are shown.
In addition, relevant presence and heading lights (sidelights and a stern light) must be visible if the boat is moving through the water.
Switch between day and night to compare it with the equivalent day shapes.
Vessels being used for diving are also covered in this rule. They are pragmatic about the likely size of the boats being used, recognising that displaying the default day shapes required for underwater operations might not be practical. It provisions for smaller vessels (although it doesn’t specify size) being used for diving to display a flag, but there are some rules around the details.
Day shape for vessels with a diver down
Once there is a diver in the water, the vessel should display a rigid replica of the International Code flag ‘A’, at least 1m in height by day.
Switch between the dive boat with and without a diver down.
Another vessel type covered by Rule 27 is dredging or other underwater operations vessels, such as a cable layer. When engaged in its activity, it has a problem with manoeuvrability, possibly even attached to the seabed. It may be sufficient to display the standard lights for restricted in its ability to manoeuvre; however, the rule also provides the ability to communicate additional, helpful information.
Day shape
At first glance, the day shape of a dredger looks complicated; however, when broken down is straightforward.
As any other vessel restricted in her ability to manoeuvre, it displays the generic ball over a diamond over a ball.
Additionally, to help onlookers, two balls are displayed on the side she is working and two diamonds on the side it is safe to pass.
Lights
As with day shapes, at first glance, the lights for a dredger look complicated; however, when broken down are relatively straightforward.
Firstly, it displays the all-round red over white over red lights needed for restricted in ability to manoeuvre.
Additionally, to help onlookers, two all-round red lights are displayed on the side she is working and two all-round green lights on the safe side to pass.
Switch between night and day to compare day shapes and the different potential statuses of a dredger engaged in dredging.
A vessel engaged in mine clearance is best avoided! Hopefully, we won’t encounter one, but Rule 27 caters to vessels involved in mine-clearing operations. It deviates somewhat from the other shapes and lights in that whilst it is restricted in its ability to manoeuvre, it’s not just an extension of the standard day shape or lights used for other vessels under this rule.
The rule book outlines that it is dangerous to approach within 1000m of the mine-clearing vessel.
Day shape
The specific day shape for a vessel engaged in mine clearance is three black balls displayed in a triangle formation.
Lights
The specific lights for a vessel engaged in mine-clearance is three all-round green lights forming a triangle.
It must also show any size-appropriate general lights, such as sidelights, masthead, or anchor lights.
Switch between day and night to compare it with the equivalent day shapes.
