Overcoming Visibility Restrictions In Ships Navigation- Containerships Cargo Stowage and Planning Guide
The risk of collision has always accompanied marine transport. Despite
improved navigating equipment, this risk is even higher today due to the growing
number of bigger and faster vessels. For this reason, seagoing vessels with the keel laid
on, or after 1 July 1998, meet strict requirements concerning the visibility from
the navigation bridge.
The view of the sea surface from the conning position is not to be obscured by more
than 2L or 500m, whichever is less, forward of the bow to 10° on either side for all
conditions of draft, trim and deck cargo under which the particular vessel is expected
to operate.
From the main steering position, the horizontal field of vision extends over an arc
from right ahead to at least 60° on each side of the vessel.
The horizontal field of vision from the conning position is to extend over an arc of not
less than 225°, that is, from right ahead to not less than 22.5° abaft the beam on either
side of the vessel.
From each bridge wing, the horizontal field of vision is to extend over an arc of at
least 225°, that is, from at least 45° on the opposite bow to right ahead and from right
ahead to the right astern through 180° on the same side of the vessel. The vessel’s side is
to be visible from the bridge wing.
The surface of the water must be visible one ship length forward from conning positions
Nos 1, 2, and 3, when the vessel is laden. If the vessel is in ballast condition, the surface of
the water must be visible 1.5L forward.
Despite these requirements, checking the ship visibility is often limited to define just
two visibility lines: one according to SOLAS and another one as required by Panama Canal
(for one L). Both lines for the ship without Trim and on full draught only. Any change of
draught and/or Trim will destroy such theoretical visibility. For this reason, the master shall
be provided with a detailed analysis of visibility, taking into account various deck cargo arrangements, various values of Trim and draught.
All new vessels shall be provided with a Loading and Stability Manual containing
a reasonable number of the Visibility Tables showing blind sectors as a function of
draught and Trim. Another option is to provide ships with a separate Visibility Plan used
as an appendix. The Visibility Plan shall be prepared as a part of As Build Drawings. It
should contain the classification drawing Navigational Bridge Visibility and the Visibility
Tables.
Visibility from Navigation Bridge must conform with the IMO requirements and additionally to special needs like those for Panama Canal, etc., as applicable.
Reducing the vessels Trim or changing the Deck Cargo Stowage may be required to reduce the blind sector within limits.
Extract from SOLAS 1974 (as amended) Ch V Regulation 22
Navigation bridge visibility :
Ships of not less than 45 m in length, as defined in regulation III/3.12,
constructed on or after 1 July 1998, shall meet the following requirements:
The view of the sea surface from the conning position shall not
be obscured by more than two ship lengths, or 500 m,
whichever is less, forward of the bow to 108 on either side under
all conditions of draught, trim and deck cargo;
No blind sector, caused by cargo, cargo gear, or other
obstructions outside of the wheelhouse forward of the beam
which obstructs the view of the sea surface as seen from the
conning position, shall exceed 108. The whole arc of blind sectors
shall not exceed 208. The clear sectors between blind sectors
shall be at least 58. However, in the view described in .1, each
individual blind sector shall not exceed 58;
The horizontal field of vision from the conning position shall
extend over an arc of not less than 2258 that is from right ahead
to not less than 22.58 abaft the beam on either side of the ship;
From each bridge wing, the horizontal field of vision shall
extend over an arc of at least 2258 that is from at least 458 on the
opposite bow through right ahead and then from right ahead to
right astern through 1808 on the same side of the ship;
From the main steering position, the horizontal field of vision
shall extend over an arc from right ahead to at least 608 on each
side of the ship;
The ship’s side shall be visible from the bridge wing;
The height of the lower edge of the navigation bridge front
windows above the bridge deck shall be kept as low as possible.
In no case shall the lower edge present an obstruction to the
forward view as described in this regulation;
On deck cargo stowage may affect bridge visibility if not appropriately planned
The upper edge of the navigation bridge front windows shall
allow a forward view of the horizon, for a person with a height
of the eye of 1,800 mm above the bridge deck at the conning
position, when the ship is pitching in heavy seas. The
Administration, if satisfied that a 1,800 mm height of eye is
unreasonable and impractical, may allow reduction of the height
of eye but not to less than 1,600 mm;
Windows shall meet the following requirements:
.9.1 To help avoid reflections, the bridge front windows shall be
inclined from the vertical plane top out, at an angle of not less
than 10 8 and not more than 25 8 ;
.9.2 Framing between navigation bridge windows shall be kept to a
minimum and not be installed immediately forward of any
work station;
.9.3 Polarized and tinted windows shall not be fitted;
.9.4 A clear view through at least two of the navigation bridge
front windows and, depending on the bridge configuration, an additional number of clear-view windows shall be provided at
all times, regardless of weather conditions.
Ships constructed before 1 July 1998 shall where practicable, meet
the requirements of paragraphs 1.1 and 1.2. However, structural alterations
or additional equipment need not be required.
On ships of unconventional design which, in the opinion of the
Administration, cannot comply with this regulation, arrangements shall be
provided to achieve a level of visibility that is as near as practical to that
prescribed in this regulation.
