Rule 3 - General Definitions | Colregs 1972 | Rules of the road | Merchant Navy |

COMMENT:
The definitions given in Rule 3 are those which have general applications throughout
the Rules. Definitions concerning lights and whistle signals are given in sections C
and D (Rules 21 and 32).
(a) and (b) Non-displacement craft, WIG craft and seaplanes are to be considered as
power-driven vessels by the definitions of Rules 3(a) and 3(b); specific responsibilities of WIG craft
vessel’. For instance a power-driven vessel engaged in trawling must not show
the two masthead lights specified by Rule 23, nor give the sound signals
prescribed in Rule 35(a) and (b), and is not required to keep out of the way of
a sailing vessel or a ‘power-driven vessel’ on her starboard side which is crossing
so as to involve risk of collision. However, all power-driven vessels, including
hampered vessels, would probably be expected to have their engines ready
for immediate manœuvre in restricted visibility (Rule 19(b)) and to alter course
to starboard when meeting a power-driven vessel of the same category end-on
(Rule 14).
(d) The phrase ‘which restrict manœuvrability’ in the definition of ‘vessel engaged in
fishing’ makes it clear vessels fishing with a few short lines or other small gear
(e) Non-displacement craft are not to be considered as seaplanes for the purpose of
Rule 18(e).
6 A Guide to the Collision Avoidance Rules
(f) For a vessel to be considered ‘not under command’ there must be some exceptional circumstances, such as breakdown of steering gear, or loss of propulsion power,
resulting in a restriction of her ability to manœuvre as required by the Rules of Part B

At the 1972 Conference it was considered that adverse weather conditions seriously affecting a vessel’s ability to manœuvre would be exceptional circumstances.
However, the fact that a vessel’s ability to manœuvre is affected by weather conditions does not necessarily mean that she is not under command. The conditions must
be so exceptional, with respect to the particular vessel, as to render her unable to keep
out of the way of another vessel by alteration of course and/or speed in order to justify
the showing of not under command signals.
In addition to vessels which have had a breakdown of engines or steering gear, or
which have lost a propeller or rudder, examples of vessels which are likely to be
accepted as being not under command under the 1972 Rules are: a vessel with her anchor
down but not holding, a vessel riding to anchor chains with anchors unshackled, and
a sailing vessel becalmed.
In the case of Glamorgan–P. Caland, 1893, it was held in the House of Lords that
the P. Caland was not justified in exhibiting the not under command lights. The speed
of the P. Caland had been reduced from 11 knots to about 4 to 5 knots by an accident
to the machinery. The Glamorgan, seeing the red lights but not the side lights of the
P. Caland, steamed towards her to offer assistance and collided with her. Lord Herschel, the Lord Chancellor, said:


(g) A definition to cover vessels engaged in operations which restrict manœuvrability
is necessary as such vessels form one of the categories referred to in Rule 18 which
specifies responsibility for keeping out of the way.

(h) In 1968 IMO recommended (Resolution A 162 IV) that ‘deep draught vessels’ in
open waters, using channels which they would be unable to leave without risk of
grounding, should show the signals which are prescribed in Rule 28, so that they
could be recognised by other vessels.
At the 1972 Conference it was decided to include provisions relating to the so-called
deep draught vessels in the Rules. In considering how to define this type of vessel it
became apparent that it would not be satisfactory to specify a minimum size or
draught and it was decided not to restrict this category to very large ships. The more
appropriate term ‘vessel constrained by her draught’ was therefore used.

A vessel is only considered to be at anchor when the anchor is down and is holding.
Vessels using an anchor to turn in the river, or riding to their chains with anchors
unshackled, or dredging with the tide, or dragging their anchors have been held to be
under way.
(k) In Rule 11 it is stated that the Rules in Section II of the Steering and Sailing Rules
(Rules 12–18) apply to vessels in sight of one another.
They do not apply to vessels which have detected one another by radar but are not in
visual sight.
(l) Sandstorms are included in the list of different conditions restricting visibility.
Examples of ‘other similar causes’ are smoke from any vessel, afloat or ashore,
including your own, and dust storms.
WIG craft look like aircraft, but are not aircraft and therefore the definition of
‘seaplane’ is not applicable to WIG craft. WIG craft are classified as dynamical
support craft. The weight of a WIG craft in operation is mainly supported by
a dynamic air cushion, which by engine thrust is created between the lower surface of
an air foil and the water surface.