When Rule 19 applies
Rule 19 applies to vessels not in sight of one another when navigating in or near an area of restricted visibility: fog, mist, heavy rain, snow or anything else that cuts visibility. Note the “near”: a ship in clear weather approaching a fog bank is already bound by it.
The moment two vessels can see each other, the ordinary rules for vessels in sight of one another (Rules 11 to 18) take over again.
There is no stand-on vessel
This is the key idea, and a favourite exam question. The give-way and stand-on rules only apply to vessels in sight of one another. In restricted visibility, a sailing vessel has no right of way over a ship, and nobody is entitled to hold their course and speed. Every vessel has the same duty: to avoid a close-quarters situation.
What Rule 19 requires, part by part
19(b): safe speed and engines ready
Proceed at a safe speed for the conditions, and a power-driven vessel must have her engines ready for immediate manoeuvre. For a yacht under sail, that means having the engine ready to start.
19(c): keep the conditions in mind
When following the general rules on lookout, safe speed and risk of collision (Rules 4 to 10), take proper account of the restricted visibility.
19(d): a contact detected by radar alone
If you detect another vessel by radar alone, work out whether a close-quarters situation is developing or a risk of collision exists. If it is, take avoiding action in ample time. If that action is an alteration of course, avoid so far as possible:
- an alteration to port for a vessel forward of the beam, other than one you are overtaking;
- an alteration towards a vessel abeam or abaft the beam.
19(e): a fog signal heard forward of the beam
Unless you have determined that no risk of collision exists, if you hear the fog signal of another vessel apparently forward of your beam, or can't avoid a close-quarters situation with a vessel forward of the beam, you must reduce speed to the minimum at which you can keep your course. If necessary, take all way off, and in any case navigate with extreme caution until the danger of collision is over.
Why turn to starboard for a contact ahead?
The other vessel can't see you either, and is likely to follow the same rule. If both of you turn to starboard, you open the distance. If one turns to port and the other to starboard for a vessel ahead, you can turn straight into each other. That is what happened when the Andrea Doria and the Stockholm collided in 1956: one turned to port, the other to starboard.
Sound signals in fog
Rule 19 works together with Rule 35, the sound signals in restricted visibility. A power-driven vessel making way sounds one prolonged blast at intervals of no more than two minutes, and two prolonged blasts if she's stopped and making no way. A sailing vessel sounds one prolonged blast followed by two short. Test yourself on the sound signals quiz.
What a yacht should actually do in fog
- Fix your position immediately, before the visibility closes in completely.
- Slow down to a safe speed, and get the engine ready to use straight away.
- Post a dedicated lookout, and listen as well as look: switch the engine off briefly to listen if you can.
- Sound the correct fog signal, and make sure your radar reflector is hoisted.
- Use radar and AIS if you have them, but remember small craft may not show on either.
- Get the crew into lifejackets, and have the liferaft and grab bag ready.
- Keep out of shipping lanes. Consider heading for shallower water, where big ships can't follow, if it's safe to do so.