Part B – Steering and Sailing Rules
Section I – Conduct of Vessels in any Condition of Visibility
Rule-8: Action to Avoid Collision
(a) Any action to avoid collision shall be taken in accordance with the rules of this Part and, if the circumstances of the case admit, be positive, made in ample time and with due regard to the observance of good seamanship.
This rule tells how the avoiding action must be executed, not which vessels are required to take the avoiding action.
Shall, if the circumstances of the case admit: ‘Shall’ is a mandatory word. ‘Shall’ is used to emphasize the need for positive action to be taken in ample time. ‘If the circumstances of the case admit’ is an escape clause though.
Positive, made in ample time, with due regard to the observance of good seamanship:
These are indefinite terms.
Positive: Positive action is a significant change in vessel’s course and/or speed. A large alteration of course or speed to avoid a collision indicates that the intention of the action is positive. A vessel’s positive action becomes easily evident to others observing her.
Ample Time: In this rule, action shall be taken in ample time means that an action shall be taken in a time so that a collision can be avoided. This paragraph didn’t say action is to be taken in ample time to avoid a close quarter’s situation. If we compare ample time and good time, we can say that ample time is meant for avoiding a collision and good time is meant for avoiding a close quarter’s situation. So, as per RoR, good time occurs much earlier than ample time.
Good observance of Seamanship: Some examples of good seamanship have been mentioned in discussions for Rule-2. Do not take an action which makes the situation worse for any other ship in the vicinity; assess what they may have to do.
(b) Any alteration of course and/or speed to avoid collision shall, if the circumstances of the case admit, be large enough to be readily apparent to another vessel observing visually or by radar; a succession of small alterations of course and/or speed should be avoided.
Let the other vessel know what you are doing. Make it obvious by sight in good visibility and obvious on the radar screen in areas of restricted visibility. Give the proper manoeuvring signals if operating under the International Rules.
(c) If there is sufficient sea room, alteration of course alone may be the most effective action to avoid a close-quarters situation provided that it is made in good time, is substantial and does not result in another close-quarters situation.
Alteration of Course Alone: Two variables can be altered to avoid collisions: Course and Speed. On larger vessels, change of speed may take a considerably long time, especially when the engines are not ready for manoeuvring but you need to change speed immediately. That’s why, this paragraph allows for a course change alone, which can be made directly and immediately from the bridge. Alterations of speed take longer to put into effect than alterations of course so they are less likely to be readily observed by other vessels
Close-quarters situations: There is no definition of Close-quarters situations. But generally we can suppose that it’s a situation between two vessels when action taken by one vessel may not be sufficient to avoid the collision. In rivers, harbours, and other inland waterways; close-quarters situations are unavoidable. The term close-quarters situation has been implied in Rule-7(CPA distance which helps assess a risk of collision), Rule-8d (safe distance – the minimum passing distance permitted by the Rules) and Rule-16 (well clear – the minimum passing distance permitted by the Rules). Both terms ‘Safe Distance’ in Rule-8(d) and ‘Well Clear’ in Rule 16 represent a greater distance than ‘close-quarters’.
In a close-quarters situation, decisions might have to be taken without time for proper thought.
Good time: Good time means ‘early’. There is no specific time at which good time begins. It’ll depend on a particular situation. Manoeuvres taken to avoid a close-quarters situation should be taken at a time when the responsible officer does not have to make a quick decision or a decision based on inadequate information. We can say that if a vessel fails to take action in good time, she may find herself in a close-quarters situation. This paragraph didn’t say action is to be taken in good time to avoid a collision.
Substantial: Alterations of course alone should be substantial so that they may be readily apparent to another vessel. In restricted visibility, alterations of course and speed should be substantial so that they may be readily apparent to another vessel observing visually or by radar. While taking an action to void a close quarter’s situation with one vessel, the OOW must monitor her action properly so that the action doesn’t result in another close quarter’s situation.
(d) Action taken to avoid collision with another vessel shall be such as to result in passing at a safe distance. The effectiveness of the action shall be carefully checked until the other vessel is finally past and clear.
Safe Distance: What distance is safe depends on the circumstances; suffice it to say that if you are obligated to take the action, the person on the other vessel should not feel compelled to act also to increase the distance still further.
Effectiveness of the Action: If action to avoid collision is required, the mariner must take effective and readily apparent action, whether it be a course change or a speed change or a combination of the two. A course change works better for meeting situations, whereas for vessels crossing at near-right angles, a speed change (perhaps in combination with a course change) often works better. Continuing change of compass bearing would be one indication of the initial effectiveness of the avoiding action. However, an appreciable change of bearing may not be sufficient to establish that the vessels will eventually pass clear of one another. Subsequent action by the other vessel could result in renewed risk of collision.
Finally Past & Clear: It means RoC doesn’t exist anymore. The visible signs are appreciable change in compass bearing, increasing CPA & distance, Etc.
(e) If necessary to avoid collision or allow more time to assess the situation, a vessel shall slacken her speed or take all way off by stopping or reversing her means of propulsion.
When a vessel is obliged to take action to avoid collision with another vessel which is crossing, or which she is overtaking, she may be prevented from making course alterations due to lack of sea room or to the presence of other vessels; in such circumstances it will be necessary to slacken speed or take all way off. In restricted visibility when a close quarters situation cannot be avoided with a vessel forward of the beam, or a fog signal is heard forward of the beam, it will usually be necessary to reduce speed or stop the ship. The speed must also be reduced if it is necessary to allow more time to assess the situation (As per Rule-5, a full appraisal of situation is required)
Taking all way off or reversing propulsion: You should refer to ship’s manoeuvring booklet to know about her manoeuvring characteristics. An OOW should have thorough knowledge about the turning circle of the vessel. It’s a good practice that the bridge team is briefed about the limitations of M/E and the procedures of stopping M/E in case of an emergency. Stoppage time (Sea ahead to zero speed) depends on various factors, such as size of the vessel, present displacement, depth of water, wind, sea conditions, current, etc. Usually the maximum astern power is 60-80% of maximum ahead power.
Helm Action in stopping the vessel: Helm action taken in the initial stage of a crash stop, when still moving at high speed, will result in a considerable increase of resistance and reduce the stopping distance. A method which may be used in some circumstances is to put the helm hard over one way then hard over to the other side with the engines on dead slow ahead, then to put the engines full astern. This should reduce the period of applying astern power so that the vessel is less likely to be slewed in the final stage.
Crash Stop: To avoid an imminent danger like collision, grounding etc, it becomes necessary to stop the vessel as soon as possible. Crash manoeuvring is turning the engine in opposite direction to reduce the ahead speed of the ship. After certain time, the ship stops and starts steaming in astern direction. The procedures of crash stop are as below (it may vary from ship to ship):
• The bridge informs about the emergency situation and requests E/R for crash stop
• The Fuel Lever (Starting Lever) is set to Stop Position and the helm is put hard-over to either port or starboard so that speed drops faster. After the stoppage, she may come off the original course line by large amount. For right handed propelled ship, the bow will cant to starboard.
• Avoid attempting Emergency Stop of M/E since it takes some times to reset parameters of M/E before a restart is possible
• After putting the Fuel Lever to stop position, observe the M/E rpm indicator. The rpm will still be showing for few minutes since the propeller doesn’t stop instantly even after the Fuel Lever is set to Stop Position. At that point, engineers will give stern movement by air only (often called as brake air), i.e. no fuel will be used. This movement is given for a very short period to stop the movement of the crankshaft or the propeller. Ship’s speed (by momentum) will be dropping slowly and few minutes after stop command is given, the rpm will show Zero.
• When the rpm rests to zero, order full astern directly regardless of whatever speed the vessel might be proceeding with at that moment
• Finally, the vessel will start to get stern-speed slowly.
Damage to Engines: In this type of manoeuvring, the main engine is subjected to severe stress and load. To avoid the damage to M/E through a crash stop manoeuvre and provided that time permits to avoid the danger, it is suggested that a quicker and safer way to stop a vessel would be to stop the engines instantly then, after a delay of three minutes or so, to give slow astern, half astern and full astern, thus avoiding acute cavitation. More recent evidence from ship trials and model tests seems to indicate that many vessels, especially those fitted with diesel engines, could best be stopped by giving ‘full astern’ as soon as possible, but it can generally be said that even if the engines can be made to go astern within one minute of the order ‘stop’ the retarding effect would be small and the risk of damage to the machinery would be great. The above remarks apply to a vessel moving at high speed. The engines can be more readily reversed when the speed is low. For the interest of safety, OOW or Master must not hesitate to do a crash stop.
(f)(i) A vessel which, by any of these rules, is required not to impede the passage or safe passage of another vessel shall, when required by the circumstances of the case, take early action to allow sufficient sea room for the safe passage of the other vessel.
Not to impede to avoid development of RoC: Vessels directed “not to impede” other vessels should take early action to keep clear by wide margins so that a RoC doesn’t develop. The other vessel shouldn’t become concerned enough to alter its course or speed, or otherwise feel obligated to act differently from the way it would if the would-be impeding vessel weren’t there.
(ii) A vessel required not to impede the passage or safe passage of another vessel is not relieved of this obligation if approaching the other vessel so as to involve risk of collision and shall, when taking action, have full regard to the action which may be required by the rules of this Part.
What if RoC exists: The vessel that had been originally directed to not impede the other should retain that burden even after risk of collision arose. That does not mean, however, that the (usually larger) vessel that was not to be impeded continues to have the right of way. If the not-to-be-impeded vessel would be the give-way vessel under the general rules, it has the duty to stay out of the way of the impeding vessel after risk of collision arises because of the application of Rule 17(a)
(i). Early action in compliance with Rule 8(f) is compatible with Rule 17(a)(ii), which permits action by the stand-on vessel. The impeding vessel also continues to have a duty to stay out of the way after risk of collision arises, and does not gain the stand-on status that the general rules might have given it. Both vessels would be obligated to stay out of the way and the impeding vessel would have a double duty to stay out of the way.
Example # 1: When a power-driven vessel and a sailing vessel are approaching each other, the power-driven vessel is required by Rule 18(a) to keep out of the way when risk of collision begins to apply, although she may be proceeding along a narrow channel or traffic lane, but this does not relieve the sailing vessel of the obligation to take early action to allow sufficient sea room.
Example # 2: If one of two power-driven vessels, crossing so as to involve risk of collision, is required not to impede the passage of the other vessel, she must, in compliance with Rule 8(f), take early action to allow sufficient sea room for the safe passage of the other vessel although the other vessel may be required by Rule 15 to keep out of the way.
Full regard to the action: A vessel taking action as per Rule 8(f)(ii) shall take into account the possibility of both vessels taking conflicting actions when there is risk of collision. However, as it is not possible to establish the precise distance apart at which risk of collision begins to apply, a vessel taking early action not to impede should also have full regard to the action which may be taken by the other vessel (as a give way vessel). Rules 14, 15 and 17(c) indicate the form of action to be taken.
(iii) A vessel the passage of which is not to be impeded remains fully obliged to comply with the rules of this part when the two vessels are approaching one another so as to involve risk of collision.
A not-to-be-impeded vessel is not relieved of her obligation to comply with the Steering and Sailing Rules when there is risk of collision. When vessels are in sight of one another and risk of collision exists, a power-driven vessel may be required to keep out of the way of the vessel required not to impede in accordance with Rules 13, 14, 15 and 18(a). In restricted visibility such a vessel is not relieved of her obligation to take avoiding action in ample time when a close quarters situation is developing. When there is an obligation not to impede in restricted visibility Rule 19 applies fully, together with Rule 8(f).