Pilotage plans and harbour entry

Pilotage: navigating with your eyes up

So far in this module you have worked at the chart table: a course to steer that allows for the tidal stream, an allowance for leeway, and a fix every so often to check progress. Close to land that rhythm breaks down. In a harbour approach the dangers are close, a mark comes up every few minutes, and the decisions — is that the right buoy? turn now? — come faster than you could ever plot them. Navigating by eye in confined water like this is pilotage.

The secret of good pilotage is that the thinking is done before you arrive. At the chart table, in harbour or on passage while there is time, you prepare a pilotage plan: a short, simple description of the way in, leg by leg, with everything you will need to check. On deck you don’t plot at all. You look up, compare what you see with the plan, and tick things off.

Plan at the chart table. On deck: look, compare, tick off.

The approach to Port Kerran

This lesson builds a complete plan for entering Port Kerran on the practice chart. Before reading on, look at the approach and find each of these:

• Kerran Approach buoy (LFl10s): a safe water mark with navigable water all round it, the usual start of the approach.
• No 1 (Fl G 5s) and No 2 (Fl R 5s): the first pair of lateral marks, 1.6 M north of it and 5.4 cables apart.
• No 3 (Fl(2) G 5s) and No 4 (Fl(2) R 5s): the inner pair, another 6.5 cables on, 4.9 cables apart.
• The leading lights (Oc 4s, front 6 m, rear 14 m), in line on 000°T straight up the middle of the channel and into the narrow inlet where the harbour lies.
• Mew Rock, which dries 1.2 m, marked by an isolated danger beacon (Fl(2)5s), 2.9 M north-west of the Approach buoy; and the wreck (4.2 m), 3.3 M west-south-west.

The direction of buoyage runs from seaward into the harbour, so going in you keep the green cones to starboard and the red cans to port (Lesson 16). The channel is deep — more than 20 m all the way to No 3 and No 4 — but beyond them the inlet shoals quickly through the 10 m, 5 m and 2 m contours to a drying head.

Building the plan, leg by leg

Break the way in into legs, each from one point you can recognise — a mark, or a pair of them — to the next. For each leg the plan gives:

1. The heading, in °M for the steering and hand-bearing compasses, with the true figure beside it.
2. The distance and the time it should take, so you know when the next mark is due.
3. What you expect to see: the next marks, what they look like and where they will appear.
4. The depth you expect, and the reading that would tell you something is wrong.
5. Checks and decisions: clearing bearings, transits, and where you will stop and think.

The other legs are worked the same way. At 5 kn the whole approach takes about 37 minutes:

Covering the dangers on the way in

The plan starts at the Approach buoy, but you have to get there. Arriving from the south, you may have to tack, and if you arrive on the ebb, diamond A shows the stream setting west-south-west — towards the wreck and Mew Rock. Rather than plotting fixes to check, give yourself a limit you can check by eye: a clearing bearing (Lesson 13) on the church spire, which you can see above the head of Kerran Bay.

Lesson 13 drew one for Mew Rock: spire NMT 033°T. But a clearing bearing guards only the danger it was drawn for, and far out that line passes only 1.8 cables from the wreck. This plan needs one line that clears both.

The tide at your arrival time

A pilotage plan is written for a time. Suppose you plan to reach the Approach buoy at 1535 BST on 4 June 2027. The Port Kerran table is in UT; adding an hour for BST gives LW 1025 BST 1.1 m and HW 1635 BST 4.5 m. You arrive an hour before high water, on a range of 3.4 m — between neaps and springs.

Off the line it is a different story. Over the inlet’s 2 m contour you would need 2.3 − 2 = 0.3 m of tide, and the head of the inlet dries. The plan keeps you on the line and ends off the harbour; beyond that, use the harbour’s own information from the almanac or pilot book.

The stream across the channel

Check the stream too. Diamond A, 1.9 M east of the approach, gives 070°T at HW−1: 1.2 kn at springs, 0.6 kn at neaps — about 0.9 kn for today’s range (Lesson 28). That sets you across the channel from west to east. To make good 000°T at 5 kn, the vector triangle of Lesson 29 gives a heading of about 350°T (353°M), making 5.2 kn over the ground.

Decision points and back-ups

Decide in advance where you will stop and think, and what you will do if something isn’t right. Port Kerran’s plan has three decision points and one way out.

• At the Approach buoy: go or no-go. Can you identify No 1 and No 2 and the leading lights? Is the visibility good enough to pick up each pair of buoys well before you reach it? If not, don’t start: the safe water mark has navigable water all round it, so stand off in the deep water there and sort it out.
• At No 1 and No 2: all as planned? Lights in line, the sounder over 24.3 m, the time about right. If anything disagrees, turn back.
• At No 3 and No 4: the last easy turn. Beyond them the inlet closes in towards the harbour, where the water deeper than 5 m is only about 2.7 cables wide, with shoal water and the drying head beyond. There is less room to turn, so commit only if all is well.
• The way out: 180°T (183°M) back down the line with the lights in line astern, to the deep water round the Approach buoy.

If a mark is missing

Buoys can drag, be damaged, or be moved or withdrawn (changes are published in notices to mariners), and a light can fail. Don’t go hunting for a missing buoy — but don’t simply assume it’s missing, either. Use the rest of the plan:

• The leading line gives your track.
• The depth confirms you are in the deep channel.
• The time tells you how far you have come.
• A check bearing tells you where you are along the line. Mew Rock beacon is due west of a point on the line 2 cables past No 1 and No 2: when it bears 273°M, you are there, with 4.5 cables to go to No 3 and No 4.

If you can’t identify the leading lights — a light can fail, and by day the structures can be hard to pick out against the land — the church spire stands almost on the line, bearing about 002°M from anywhere in the channel. That is a reasonable back-up for the track, as long as the buoys and the depth agree with it.

Writing the card and using it on deck

Keep the plan simple and big. A sketch on a card or a notebook page, in a waterproof sleeve, works better than a page of tables: draw the way in as a line of arrows from mark to mark, with the heading in large figures beside each leg, the distance and time, the marks with their characteristics, the clearing bearing with its NMT or NLT, the warning depth and the way out. Leave out anything you won’t need on deck.

Who does what

• The helmsman steers — keeping the leading lights in line — keeps a lookout ahead, and says so if anything looks wrong.
• The navigator holds the plan, picks out each mark early with binoculars, calls it before it arrives (“No 3 and No 4 fine on the bows, about six cables”), ticks it off with the time, takes check bearings and watches the depth sounder.
• Short-handed, brief the crew before you start, and keep the card where the helmsman can see it.

Ticking off

Every time you pass a mark, tick it off with the time, and compare the time with the plan: 1554 for No 1 and No 2, 1602 for No 3 and No 4. Before each leg, say out loud what comes next and where it should appear. Glance at the depth sounder whenever you tick something off. And use every transit the plan gives you — here the leading lights — because a transit shows your track without any compass error.