Q. What action will you take upon hearing a fog signal, forward of your beam?
Ans. Assuming that all the restricted visibility precautions are already being taken, I will ask the lookout person to try to visually locate the vessel whose sound signal is heard. There can be two situations:
- Own vessel has operational radar.
- Own vessel has no operational radar.
With operational radar:
In the first situation, with operational radar, most probably the target is already under observation and the sound signal is heard as the target passes by. Probably, the action has already been taken earlier. The target must be watched and caution observed until it is past and clear. In a rare situation, a signal may be heard with no echo appearing on the radar screen. This may happen because of improper tuning; excessive clutter control; a small vessel or vessel approaching within blind sector; etc. The first priority is to establish the target on radar screen. I will use radar on different ranges, check the display on second radar, etc. I will increase frequency of sounding own fog signals, without changing basic characteristics of sound signal.
No operational radar:
Hearing a fog signal forward of the beam without an operational radar is a serious matter. Actually, a ship without operational radar must not venture out and do any kind of navigation. It might however so happen that during a passage, the radar becomes in-operational. If such is the case, the safety message must be given out immediately and the Port Control must notified. In the safety message, the name/call sign, position, the type of problem and intended course and speed should be included. The Traffic Management Services must be informed, if any. The Vessel Traffic Management Services can be very useful in regulating the traffic. VTMS can caution the vessels in area, of any special situation developing. It can caution the ship, if seen running into danger.
Whenever a fog signal is heard, it means a target vessel is most likely within a range of two miles. The direction of incoming signal may considerably change. Hence, the actual direction of target may be different than that, indicated by sound signal. The danger is grave if the collision / close quarter is not ruled out with a vessel forward of own beam (being, within two miles). If vessels are converging, which can definitely be the case, a collision may be only five to ten minutes away.
In restricted visibility, as the sound signal is heard forward of beam, in the following situations, the collision is not ruled out:
1. Though, radar operational, there is no clear CPA.
2. Radar is not operational.
3. There is no clear assessment of situation.
Rule 19 (e), applies, I shall reduce the speed to minimum at which she can be kept on her course. If necessary, I shall take all her way off and in any event navigate with extreme caution until danger of collision is over. Alteration of course should not be made but vessel must be ready to carry out any maneuver.
Q. Why, you (with no operational radar) must reduce your speed to minimum for a vessel whose fog signal say ‘one prolonged blast’ is heard, forward of your beam?
Ans. If the target vessel has operational radar, she will mostly alter her course to her starboard in case of the risk of collision. She must have already initiated this action, probably when four miles off. Reduction of speed is an appropriate action. If she does not have operational radar, after hearing my ship’s fog signal, she will reduce her speed to minimum (just for maintaining her course). Both the ships get more time to assess the situation. There is the possibility of seeing the ship even though at close range with at least some time available prior colliding. Increase of speed must not be done. The alteration of course should be avoided after hearing a fog signal ahead. Though, vessel must be ready in all respect to take any action.
In the following diagram, with the own ship in centre and various positions of the target involving possible collision, have been considered. In each of the two figures, it appears that by following rule 19 (e), the collision will be either postponed with smaller magnitude of impact or will be averted. The diagrams however, do not cover every situation of close quarter. Thus, in figure 1, it might so happen that, earlier the vessel, which was clear, comes closer after the action. The impact of collision though, should always be less after the speed is reduced.
Q. With no operational radar with you, what action will you take for a vessel whose fog signal say ‘two prolonged blasts’ is heard, forward of your beam?
Ans. Assuming that all the restricted visibility precautions are already being taken, I will ask the lookout person to try to visually locate the vessel whose sound signal is heard. ‘Two prolong blasts’ means the vessel ahead is a power driven vessel underway but stopped and making no way through water. But one must always be cautioned that the vessel underway may start making way through water. Moreover, the actual direction of the vessel may be different from the direction of incoming signal. Since, the risk of collision is not ruled out, I will take action as guided by rule 19(e) i.e. I shall reduce the speed to minimum at which she can be kept on her course. If necessary, I shall take all her way off and in any event navigate with extreme caution (which may need reversal of propulsion or immediate alteration upon making a better assessment of situation) until danger of collision is over.
Q. What action will you take upon hearing a fog signal, from abaft your beam?
Ans. Assuming that all the restricted visibility precautions are already being taken, I will caution the lookout person and try to visually establish the vessel, whose sound signal is heard. There can be two situations:
- Own vessel has radar operational.
- Own vessel has no operational radar. The safety message and report to VTMS would have been given.
The TCPA of a vessel abaft the beam could be about an hour, if her speed is two knots more than own ship’s speed. TCPA may be less, though. If own ship has operational radar, then if the target is an overtaking vessel, she should be watched carefully until finally past and clear. In case an alteration of course is needed to avoid collision or close quarter situation then so far as possible, I will avoid altering the course towards the overtaking vessel.
If the echo does not appear on radar then it can be because of improper tuning; excessive clutter control; or a small vessel approaching within blind sector. Without losing any time the target must be established on the radar screen. Different ranges and the display on second radar must be checked, if required. The frequency of sounding of own fog signals may be increased, maintaining the basic characteristics.
There is no mention about hearing a fog signal from abaft the beam but the following conclusions can be drawn:
- The target is about two miles off.
- The actual direction of target may be considerably different than the direction of incoming signal.
- Most likely the vessel is overtaking though she could be crossing also but TCPA is likely to be large.
- If the TCPA is small, she must be a fast vessel and most probably would be having operational radar.
- The ship must be aware about the special condition of my vessel not having radar.
A close focused lookout in the direction of incoming signal is maintained. Crew is kept standby at forward stations; engines are kept ready for maneuvering; and helm is kept on manual steering. No alteration of course and / or speed is advisable. This is because, any action taken by me, may go against the target’s action or defy the purpose of the target’s action.
Q. Don’t you think you should increase the speed?
Ans. No, this is for two reasons:
Firstly, the target vessel is aware about the safety message sent by me; secondly assuming that the vessel is overtaking with a relative speed of two knots, the relative approach speed is very low. This means that there is a very good chance of visually spotting the target well before any close quarter situation.
In any case, with the engines and steering in the state of absolute readiness, an appropriate action, which may involve alteration of course or increase of speed, may be taken to avoid collision.
Q. In restricted visibility, there are three targets; first at two points on starboard bow; second target is at 3 points on port bow and third target on starboard quarter. All of them are 7 miles off with zero CPA. What action will you take?
Ans. Probably, all the three targets are already acquired and monitored by now. Most likely the forward targets are on converging courses and the target on starboard quarter is overtaking. Assuming in this particular case, the ships are at their respective maneuvering ‘full-ahead’ speeds, the TCPAs of the forward targets may be say 20 minutes and say the TCPA of the target on starboard quarter is 3.5 hours. The rules deal with one ship at a time. In a situation as above where three ships exhibit zero CPA, the ships will be given priority as per their TCPAs. Thus, the forward targets on converging / crossing courses will be considered first. I will give a bold alteration to starboard as per rule 19(d). Both these forward targets, depending on their headings are likely to also alter courses to their starboards.
Q. How can you alter to starboard, with a target on your starboard quarter with zero CPA?
Ans. The TCPA of the target on starboard quarter is likely to be more than three hours because the relative speed may be just about 2 knots. My altering to starboard and remaining on this course for another 20 minutes or so will not cause any close quarter situation or confusion with the target on starboard quarter. My altering to starboard is not in contravention of rule 19(d) as my alteration of course is not towards a target on starboard quarter, which can pose a risk of close quarter situation.
Q. Okay, now there are three targets; first at two points on starboard bow; second target is at 3 points on port bow. Both of them are 7 miles off with zero CPA. The third target is on starboard quarter about half a mile away. All three targets are at the same TCPA. What action will you take?
Ans. Assuming that all the restricted visibility precautions are taken and that the ships are at their respective maneuvering ‘safe speeds’, let us suppose that the TCPAs of the targets is 20 minutes. This means that the relative speed of overtaking is about 1.5 knots or overtaking vessel is about 2 knots faster than own ship. Thus, let the speed of forward ships and own ships be 8 knots each. Even though the TCPA of all the targets is 20 minutes, the distance of the target on stern is only half mile.
As far as the nearest vessel and own ship is concerned, any slight mistake by anyone, can bring the ships further closer and therefore, my priority will be the most appropriate action in respect of this target. As per 19(d), as far as possible, I must avoid alteration of course towards her to starboard. The options left are considerable change of speed or a very bold alteration to port. Increase of speed will pre-pone the close quarter situation with forward vessels and the action is not favoured by many. Reduction of speed can be the best option but the action must be clearly evident to the vessel at quarter. Though, the target has option to overtake from either side, if the target on starboard quarter is clearly overtaking on the starboard, reduction of speed is very appropriate in above situation. Alteration of the course to port is not in direct compliance with the rules. In this situation Master must be called well in time and a quick and bold alteration to port (70 to 80 degrees) can be taken. Delay is taking action may complicate the situation, this is the reason that a watchkeeper must always make an early assessment of situation before he actually runs in to danger.
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