Page 35 - Collision Avoidance Rules Guide

They do not apply to vessels which have detected one another by
radar but are not in visual sight.
(1) This is a new definition but the different conditions restricting
visibility were listed in Rules 15 and 16 of the 1960 Regulations.
Sandstorms are now included. Examples of ‘other similar causes’ are
smoke from own vessel, other vessels, or ashore, and dust storms.
(m) The definition of ‘wing-in-ground (WIG) craft’ was added as an
amendment to Rule 3 by the 22nd IMO Assembly in 2001. WIG craft
are not to be considered as seaplanes or non-displacement craft. For
the pufpose of WIG craft there is a new provision included in
Rule 18(f), (see page 116).
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.
WIG craft have the capability of increasing the altitude of flight by
enlarging the engine thrust, thus performing a jump to overcome and
overfly obstacles on the earth surface. However increasing the altitude
of flight of a WIG craft to perform a jump will significantly enlarge
its fuel consumption and will therefore result in loss of economy.

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