WAYPOINT - Taking control of the ship
Dr Andy Norris, an active Fellow of The Nautical Institute and the Royal Institute of Navigation, discusses the importance of continual checks and control when handling a ship.
Fundamentally, shiphandling is all about making safe and effective navigational decisions. Since a ship’s manoeuvres are affected and limited by the vessel’s capabilities within the immediate environment (including wind, currents and sea-state), navigational decisions must take into account how the ship will actually handle in the particular circumstances. Making the best navigational decisions requires increasingly expert shiphandling knowledge as the situation intensifies.
Scientists and naval architects fully understand the detailed physics and mathematics needed to work out how a specific vessel would behave in a given set of circumstances. However, it is not practical to try and make accurate calculations of this kind during a real-life shiphandling situation. Therefore, we rely on a well-trained shiphandler to make good judgements about what actions are needed to keep the ship safe.
These decisions must be based on a mixture of experience and the expert use of proven concepts. For example, the concept of the pivot point is very important, and the handler must have a good understanding of this, including its effective position under differing circumstances.
In close situations, primary navigational concerns are the relative position of hazards and the speed and acceleration of your own ship relative to those hazards. Close situations are particularly complex because these relative values can vary significantly along both the length and beam of own vessel. Ships are too large to be considered a ‘single point’ in such situations – as is true of many hazards at sea. The question, ‘What is your location?’ is not as easy to answer as simply giving a lat/long coordinate.
Check, check and check again
To ensure your own reaction is as good as it possibly can be, it is vitally important to keep checking the correlation of all the available information. Critical information is received from many sources, including what everyone on the bridge can see, hear and feel in terms of ‘body-acceleration’. Of course, onboard electronic sensors are very important, not least those detecting changes in movement, such as rate-of-turn indicators. Information from digital and voice adio communications is also key, as well as ‘stored’ digital and paper-based data, such as charted and tidal information.
We have to be cautious about relying on data from any single source. However, if data from multiple sources is well correlated, your perception of the situation is far more likely to reflect reality. This will improve the validity of any manoeuvring decisions and make a successful outcome far more likely, even in the tightest conditions. Our safety at sea is dominated by the immediate position and movement of the vessel we are on, even if the degree of control that we have is limited by external conditions and the vessel’s specific design.
Of course, any adjustments made to a ship’s controls affecting its speed and detailed rotation must be continuously monitored against the external situation. This allows you to refine the manoeuvring action, but it also adds to and reinforces your own knowledge as a shiphandler, and will help you when you encounter similar situations in the future.
To err is human…
Although we have our own expectations about how other vessels involved in a manoeuvre will react, what they will actually do is a major unknown. It is not that the other vessels are being navigated badly – just that everybody occasionally makes mistakes. Even if the close-by vessel is being navigated with equal competence to your own, remember that with two ships, there is now double the possibility of human and machine errors that could affect your safety. Never assume that your own immediate response is the end of the situation. Keep alert…
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