3.3. Navigation in the vicinity of ice

Question 1

(a) State the areas where ice which is dangerous to navigation may be encountered and where ice accretion may be experienced

Answer 1

Areas in which dangerous ice may be encountered are:
♣ North Atlantic – (see MCA Trading Areas)
- 45 o N 28 o W heading westwards towards land.
- 61 o N 28 o W heading eastwards towards land.
♣ North Pacific - Sea of Okhotsk
(Off Kamchatka Coast) heading westwards.
♣ Southern Ocean (South of 60 Degrees)

In general, any Winter Seasonal Zone as defined by the International Load Line Convention can be considered as an area of potential ice accretion. If a vessel encounters sub-freezing temperatures associated with gale force winds ice accretion will also occur.
Ice accretion areas on a vessel will be on all horizontal and vertical surfaces on the windward side of the vessel.

Ice Accretion
Full Allowance Half Allowance
Horizontal Surfaces 30 kg/ metre 15 kg/ metre
Vertical Surfaces 15 kg/ metre 7.5 kg/ metre

Cranes and Riggings 5% of weight on vertical surfaces

Beams and Rails 10% of weight moment of ice on
vertical surfaces

Question 2

(b) State the sources from which information can be attained about Areas in which dangerous ice may be encountered

Answer 2

• International Ice Patrol broadcasts
• Coast Guard Navigation Warnings
• Navtex
• Sat C
• Dangerous Ice reports from other vessels which are
  bound by SOLAS to compile Danger Reports when
  encountering ice which may pose a hazard to
  navigation and transmit it to all vessels which may
  be in the area by any means deemed suitable.
• The Mariners Handbook (NP100) also contains
  information on ice and ice accretion Chapters 6 - 7.

Question 3

(c) State the precautions when navigating in areas of ice especially at night and in restricted visibility

Answer 3

♣ Keep moving – even if it is very slowly,
♣ Work with the ice movement and not against it,
♣ Remember excessive speed may lead to ice
damage to the ship,
♣ As it is not easy to determine the hardness of ice
encountered, it is not recommended to enter sea ice
if an alternate route is available.
♣ Enter ice at slow speed to reduce the initial impact
and increase speed only to maintain headway and
control of the ship.
♣ If a floe cannot be avoided, it should be hit squarely
on the stem.
♣ Have engines ready to go full astern at any time.
♣ Rudders and propellers are the most vulnerable part
of a ship navigating in ice. When going astern the
rudder must be kept amidships and if any ice goes
beneath the ship RPM should be reduced to dead
slow astern.
♣ If a ship is stopped in ice the rudder should be
placed amidships and the engines kept running at
dead slow ahead to wash the ice astern and keep
the stern clear for any subsequent manoeuvres
astern. Before any astern movements be sure the
rudder and propeller are clear of ice.
♣ Easy rudder movements should be used. Excessive
rudder angles should be avoided except in an
emergency as this causes the stern to swing which
may result in damage.
♣ Icebergs in a pack are current driven and should be
avoided by as wide a berth as possible.
♣ Pressure ridges should be avoided and passages
through pack ice under pressure should be avoided.
♣ All forms of glacial ice should be avoided.
♣ A ship stopped and near to shore should always be
heading seawards unless it intends to anchor.
♣ Anchoring in heavy concentrations should be
avoided.
♣ Its Unwise to follow a shore lead with onshore wind
blowing if not accompanied by ice-breaker.
♣ Navigation in pack ice during darkness should not
be attempted without good spotlights. If visibility is
reduced the vessel should be hove-to and the
propeller should be kept turning ahead.
♣ If a vessel becomes beset she should attempt to
free herself as soon as possible. This can be done
by ballast transfer forward/aft and athwartships.

Question 4

(d) Describe damage than can be sustained in areas of ice

Answer 4

1. Severe wear of the outer shell plating may be experienced at the waterline and above depending on the thickness of the ice.
2. The paintwork on the superstructure will flake and become badly pitted if a vessel remains in temperatures below freezing for an extended period of time.
3. Denting of the shell plating in way of the bow will occur.
4. The stern will be stripped clear of all paint and protective covering.
5. The rudder and propeller may be damaged by large floes passing down the ship’s side and colliding with the upper area of the rudder, the rudder stock and the propeller blade tips.