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Re: Navigation Rules
From: Trevor Kenchington
Date: 2002 Jan 13, 1:22 PM
From: Trevor Kenchington
Date: 2002 Jan 13, 1:22 PM
Lu Abel wrote: > Respectfully, my copy of the (US) Navigation Rules does not mention > anything about their "not applying to vessels in fog so dense that one > cannot be seen from the other." Rule 6 (both International and US Inland) > clearly requires vessels to "at all times proceed at a safe speed so that > she can take proper and effective action to avoid collision..." To me this > says that if the fog is so thick two vessels can't see each other, they are > both obligated to slow down or stop! Rule 6 is part of Section I -- Conduct of Vessels in Any Condition of Visibility. The priority of sail over power, however, comes under Rule 18 and that of starboard tack over port in Rule 12. Both Rules 12 and 18 are in Section II -- Conduct of Vessels in Sight of One Another. Those Rules do not apply when vessels cannot see one another on account of poor visibility, which is as it should be since (as Herbert pointed out) if you can't see a nearby vessel you have no way of knowing whether she is under power or not, let alone what tack a sailing vessel may be on. As to what to do when close to another vessel in fog too thick to see her, it is not a matter of simply extrapolating from Rule 6 but of obeying Rule 19 -- Conduct of Vessels in Restricted Visibility. In the case of the radar-plotting exercise that started this thread, Rule 19(d) would apply -- if visibility was assumed to be poor for the purposes of that exercise. "Ownship", having determined by radar that she was in a constant-bearing situation, with respect to the target ship, would be obliged to take avoiding action in ample time. Considering that the target ship was forward of "ownship's" beam (Relative Bearing 322 or Red 038) and that "ownship" was overtaking the target, Rule 19(d) would allow "ownship" to alter course in either direction -- though, following the common principle, an alteration to starboard would be preferred unless there was compelling reason to turn to port. In reality, "ownship" could expect to sight the target's stern light well before a collision occurred, making her subject to Rule 13 before the situation was resolved. (The plotting exercise only brought the two vessels to a distance of 5.4 M apart.) "Ownship" could, however, make the same alteration of course to comply with both Rules. Meanwhile, Rule 19(e) would require "ownship" to slow to the minimum speed that would give her steerage way until such time as she could determine that no risk of collision existed. (No doubt there is case law that defines how much reliance can be placed on the radar plot in making that determination but I am not aware of what it says.) Putting those together and considering the courses of the two vessels, "Ownship" might do best to slow down, turn sharply to port, and pass under the target's stern before resuming her own course. Naturally, it would be best to communicate that intention to the target vessel over VHF before altering course. Trevor Kenchington -- Trevor J. Kenchington PhD Gadus@iStar.ca Gadus Associates, Office(902) 889-9250 R.R.#1, Musquodoboit Harbour, Fax (902) 889-9251 Nova Scotia B0J 2L0, CANADA Home (902) 889-3555 Science Serving the Fisheries http://home.istar.ca/~gadus