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Section 1 — Conduct of Vessels in any Condition of Visibility
Rule 6: Safe Speed
Every vessel shall at all times proceed at a safe speed so that she can take proper and effective action to avoid collision and be stopped within a distance appropriate to the prevailing circumstances and conditions.
In determining a safe speed the following factors shall be among those taken into account:-
Meaning: A very difficult statement ‘Safe Speed’. Any vessel, which is sailing has some speed and with that, it can cause trouble for others as well as to itself. If the speed is very low and the current is strong she may drift on to any other ship, so a low speed is out under these circumstances. If the speed is more and if the steering fails then she would move away from her course line onto a danger very fast without maybe even an emergency being realised.
So ‘safe speed’ means that the ship sails at a speed at which if any emergency occurs she would come out of the emergency without anybody getting injured.
The basic fact is that under any circumstances the speed should be such that the vessel can take an effective (avoid) action to avoid danger, this includes manoeuvring to keep out of the way or slowing down or stopping to allow another vessel to pass clearly.
In the open sea, ME slow down or stopping may not be required and a manoeuvre in good (well before closing in) time would be fine, but if the sea passage is narrow or the depth is less, then ME should also be on standby. Also if the current is strong or the visibility is poor, then in open sea the ME may be required, since the time of observing the vessel may be reduced.
It is likening to a person running on a racetrack, which is brightly lit – he runs at his maximum speed. Place the same person in a forest at night and then ask him to run, obviously, he would run taking into consideration that he may hit a tree or a branch or fall in a ditch. Depending on how well he is seeing he adjusts his speed.
(a) By all vessels:-
i. The state of visibility;
The visibility, if the visibility is affected by any condition then adequate precautions should be taken and the M.E. may be required, the helmsman should also be stand by and if permissible the stand by steering motor switched on.
ii. The traffic density including concentration of fishing vessels or any other vessels;
If the traffic density is heavy, and a lot of ships are moving around then the ME has to be on standby. Since the vessel may have to take emergency measures to avoid danger. The alteration of courses may not be possible due to other vessels in the vicinity.
iii. The manoeuvrability of the vessel with special reference to stopping distance and turning ability in the prevailing conditions;
This relates to the peculiar maneuvering characteristics of different vessels, a large fully laden tanker may have stopped her engines after being on full ahead, she then takes emergency action to stop the vessel by going emergency full astern, but the momentum of the vessel is such that she would come to a full stop condition only after traveling a further distance of maybe a mile. A smaller cargo vessel or the same tanker on ballast in such a condition may have stopped in the water in a distance of maybe less that quarter of a mile.
Again a large tanker fully laden will take a lot of time to initially begin her turn after the wheel is put hard over, and once the vessel starts her swing she keeps swinging and to stop her swing it takes a lot of time wherein the ship may have done a near 360° turn and landed up in another critical situation. A smaller vessel or the same tanker on ballast may not have such problem.
iv. At night the presence of background light such as from shore lights or from back scatter of her own lights;
The above refers to the state of visibility, a vessel when she leaves a port is surrounded by a lot of bright shore lights, and her navigation lights may be cluttered up with these lights. A lookout on another vessel would not be able to see the vessel departing the port until she comes to a position where the background is dark.
The second case refers to backscatter of a vessel’s own lights. Backscatter of ships lights is the effect of a brightly lit ship (say at anchor or at sea with the bridge front port holes not covered). The light, which emanates from these sources pick up the microscopic particles of the atmosphere and they are seen as a filter before an observer’s vision. In cases where this filter is bright, it may obscure a distant vessels navigation lights and a look out may detect the vessel when she is quite close.
v. The state of wind, sea and current, and the proximity of navigational hazards;
In rough weather with high winds and waves it is difficult to quickly alter the course of a ship the wind and/or the waves prevent the alteration, as such, the helmsman used to giving a particular helm to alter a course may find that the ship either does not turn or turns very slowly, the correcting helm also is different than usual.
A current also makes a ship behave in the above manner.
A danger mark or a shallow patch would cause a vessel to alter course less than is required, as such the need for a ship to be within manageable speed, where she can be brought out of one danger without her landing up in another difficult situation.
vi. The draught in relation to the available depth of water.
As stated previously the draught in relation to the depth of water – a deep drafted vessel under the circumstances, has to take special precautions in maintaining her speed, her draft is more, thus the sea room available for her to take effective action to avoid a close quarter situation is less. Speed thus has to be controllable and the ship if required has to be stopped short of danger.
(b) Additionally, by vessels with operational radar:-
Today this refers to practically all ocean-going vessels. When it is stated that the vessel has a Radar, it implies that the Radar is fully functional and may be used to keep a Radar watch. And a good Radar lookout can be kept on it.
i. The characteristics, efficiency, and limitations of the radar equipment;
A functional Radar may not be operating at its peak performance, maybe the magnetron has become old, or the centre of the PPI is burnt out or any other causes where the Radar has got peculiarities which are readily apparent to a new observer but may be overlooked by an old ship hand. The Mast and the funnel cast Radar shadows and for a particular ship, the watch keepers have to take that into consideration. These peculiarities may in emergencies cause other vessel’s not to be tracked by the Radar.
ii. Any constraints imposed by the radar range scale in use;
Sometimes a Radar may be fully functional and good but it may have a defect that is it may not detect vessel’s at a certain range or may be not very good at low ranges or on higher ranges.
iii. The effect on radar detection of the sea state, weather and other sources of interference;
Clutter, a nuisance especially when it is least wanted. Rain clutter is the raindrops sending their reflection back to the observer who is more interested in detecting the ships. Rain clutter may completely obscure an entire region of the horizon on Radar, thus any ships within that particular region will not be detected. Increasing the Rain clutter control on the Radar will reduce the rain clutter but will also remove weak targets.
Sea clutter is another hazard, this is affecting more around the proximity of the ship than rain clutter, but the effect is the same, the vessels (especially small or when the aspect is poor) are obscured.
Other sources include soot from the funnel. Which can seriously impair the performance of the Radar.
iv. The possibility that small vessels, ice and other floating objects may not be detected by radar at an adequate range;
Every modern Radar has a selective clutter control, where the logic is that, the microprocessor within the Radar once it detects a target predicts the next position of the target, if the target fails to appear it removes the target, of course, this sequence is not in one sweep but in about 5 sweeps, thus a small vessel if it appears inconsistently, then the Radar will not detect it.
For Ice it is different, the ice reflects the EM wave in a direction that is not towards the scanner and is thus lost and the observer does not see the Ice.
v. The number, location and movement of vessels detected by radar;
In areas of high traffic density, keeping track of what each ship is doing and also assessing the ship with the most potential risk factor is a demanding task. However with a Radar tracking unit or an ARPA, the same can be achieved very easily. The only carefulness that has to be exercised is that the risk factor set data as presented by the Radar should be evaluated. And an understanding of the situation has to be done.
vi. The more exact assessment of the visibility that may be possible when radar is used to determine the range of vessels or other objects in the vicinity.
Since Radar observation is not affected to that extent as observation by sight by poor visibility, using the Radar, one should do an assessment of the visibility and note down at what range the target was actually seen by the observer.
Earlier visibility was estimated by guess work (experience some may call it), but with Radar, it is an exact figure, also visibility is not the same all around the ship especially in rain, as such more exact assessment may be done by using the Radar.