Passage through Magellan Straits (Points for consideration)
• An alternative route between E and W coast of S. America.
• There are extreme difficulties and dangers when both E and W bound.
• The dangers are those associated with narrow channels and harbour accentuated by the prevalence of bad weather and generally foul and rocky character of the anchorage.
• Extreme manoeuvrability of the vessel is important, especially in those parts of the straits where the cross tidal streams are strong or where there is heavy traffic combined with violent and unpredictable squalls.
• West bound vessels avoid adverse current, gale and head seas by using this strait to Cabot de Harnos.
• A risk of encountering icebergs is avoided and a considerable saving in distance.
• A poor landfall position.
A vessel trades throughout the year between the east coast of the USA and the Gulf of Mexico and the Caribbean Sea.
Hazards to be considered when preparing a passage plan in this area.
A vessel trades regularly to the West Indies and Gulf of Mexico.
i) hazards that may be experienced in this area, throughout the year
ii) The specific hazards found in limited periods of the year
• In coastal waters strong northerly winds may reach at times over the gulf.
• During June to November hurricanes effect the area specially N of Cuba but are rare S of 15˚N.
• During May to December there is a likelihood of heavy rain and thunderstorm and squalls reducing the visibility drastically.
• The height of the swell is large around the area 13˚N 77˚W off the Caribbean Sea especially in June/July when the frequency of the swell >4m is 20%.
• Charts are based on old surveys
• Reduced visibility in squalls
• Strong currents in Florida straits, galleon passage and yuacatan channel
• While the average current in most of the Caribbean sea are of about 1 knot increasing on the west side of
Yucatan channel to about 4 knots
• The area involves intense off shore operations especially in Gulf of Mexico. There is a dense traffic by supply vessels mobile rigs etc
• Hazards associated with submarine laying, numerous well heads, safety fairways, unlit Racons, towing
vessels and bright flares reducing visibility
• Coral growth is dense and charted depths are difficult to rely upon and also existence of banks which are steep to.
• Cruise vessel / pleasure vessel movements in narrow lanes can cause concern
• In the eastern passages of the Caribbean sea there exists strong eddies making manoeuvring difficult.
A vessel trades regularly between Japan and New Zealand, list the hazards associated with trading in this area.
There are a number of risks associated with passage Between Japan and New Zealand and they are listed below:
• The vessel will be passing through archipelagic sea lanes where the area available for navigation is narrow
and hence maintaining vessels position is of prime concern.
• Off the Eastern archipelagos there are plenty of huge Floatsam (Uprooted trees floating)
• A number of small islands will be encountered restricting regular great circle sailings
• Most of the islands are so low that it is impossible see them at night as they could also be poor radar targets and this presents the danger of the ships being driven on to the barrier or fringing reef.
• The above reefs have very deep water adjacent to them and sufficient warning by the echo sounder may not be available to take avoiding action early.
• Deep draft vessels are to navigate with extreme care around these reef areas.
• Current among the island is very strong and not of defined direction.
• Very little of the Pacific ocean has been thoroughly surveyed. Hence charted depths have to be treated with
utmost care.
• May areas exist where volcanic activity might result in the formation of new shoals in to areas which have
been well surveyed.
• Vessel will be passing through TRS prone area
• Off the coast of Japan there is a very dense fishing traffic as well as normal traffic and associated hazards.
• During the spring / summer there is also the possibility of encountering Fog and associated poor weather.
• During winter the Northern latitudes above 35˚ and also the area of around Japan is associated with gale
force winds and associated hazards
• Choice of routes around this islands are dictated by the prevailing monsoons and associated wind direction.
A vessel is to make a passage from Hong Kong to New Zealand (in October) and every appropriate track entails passing close to numerous islands and shoals.
The vessel is fitted with all modern aids to navigation.
• The vessel passes around numerous low lying islands which are poor radar targets and their visibility at night is also severely reduced.
• The vessel’s position has to be accurately maintained off these area and vessel’s position fixing methods have an accuracy of 10 – 100 metres depending on their type and the quality of service available at that time (selective availability)
• Off these island exist reefs and adjacent to the reefs is deep water. So there could be a sudden loss of depth and which could well be within the accuracy of our position fixing methods and there is a real danger of running in to the reefs.
• Continuous use of Echo sounder readings with associated alarms set for drop in soundings may mitigate the above situation but the steep drop in soundings means time available is limited to take corrective action.
• Poorly surveyed areas and charted depths can not be relied upon.
• Area of volcanic activity results in formation of shoals even over surveyed areas questioning the navigational accuracy and vessels fix.
• Old charts are available for the area and can not be relied upon entirely
• The navigational aids available are limited. Hence difficulty in maintaining position by way of transits or terrestrial bearing and navigational techniques
• The competency and complacence of the crew involved in navigating in these areas has a direct bearing on the maintenance of navigational accuracy.
• Intense currents resulting in sets which require skilled steering and navigation techniques.