Advanced Ship Handling

When the engine is gone and the ship is still making way toward danger, the anchor is not there to hold the ship — it is there to slow it down, using much the same physics that stops a runaway lorry on a gravel escape ramp. The cable, veered and dragged along the seabed under load, converts the ship's kinetic energy into friction, and usually into damage. That is the trade the anchor is making: gear for ground.

Walking back the anchor under power — lowering it on the windlass brake rather than letting it run free — keeps it under control until it is at or near the bottom, at which point it is let go and cable is veered in a short, deliberate scope. Full scope dropped at speed does not slow the ship gently: the cable comes up hard and takes the whole snub load in an instant, and something gives — usually the cable, sometimes the windlass brake or the bitts. A short scope lets the cable drag and grip progressively, converting way into friction over distance rather than into one violent jerk.

This is also why the decision sits with the master alone: it weighs the near-certain loss of expensive gear against the ship, and no checklist can make that trade for the person on the bridge. What can be worked out in advance, or in the minute available, is whether there is enough cable to do useful work before it runs out — which is exactly the question the first worked example below answers.

A dead engine in open water is an inconvenience. The same failure in a buoyed channel, with traffic astern and a bend ahead, is an emergency that has to be run as a sequence, not solved as a single problem. The bridge team's job and the engine room's job separate cleanly at the moment of failure, and both start immediately rather than one after the other.

• Inform — the engine control room reports the failure to the bridge, and the bridge in turn informs VTS or the pilot station at once, with position, heading, residual way and intentions. Traffic astern needs the same warning without delay.
• Steer — a ship without propulsion still has rudder authority for as long as she carries way through the water; use it to hold the channel or edge toward the widest, safest water while options are prepared.
• Prepare — anchors walked out ready to let go, not necessarily dropped yet, so the ship can use the last of her way and sea room before committing to the anchor as a brake.
• Call — tugs requested early; a tug that is not needed in the end costs little, one summoned too late cannot arrive in time to matter.

The habit worth building is to treat "inform, steer, prepare, call, warn" as a single drill that starts the instant the alarm sounds, rather than as five separate decisions each waiting for the last one to finish.

A ship's waterplane area is not constant as a wave passes along her length: bow and stern flare or tumble home, so the waterplane — and with it the instantaneous righting arm — narrows as a wave crest sits amidships and widens again as a trough takes its place. In ordinary conditions this barely matters. When the wave length is close to the ship's own length, and the timing of that narrowing-and-widening cycle lines up with the ship's own roll, each cycle adds a small push in the same direction as the last, and the roll grows — this is parametric rolling, a resonance, not a failure of steering.

Synchronous rolling is the more familiar cousin of the same idea: here it is the direct wave-induced heeling moment, not the changing waterplane, that repeats in time with the ship's own roll — the danger condition being an encounter period close to the full roll period, rather than half of it. Both are cured the same way: the coincidence is broken by changing speed, heading, or both, so that the encounter period moves away from the danger band. Increasing rudder activity or fighting the roll with helm alone does not address the cause, because the cause is timing, not steering.

Recognising the pattern early matters more than the arithmetic: an unexplained, growing roll in a head or following sea, with a swell period that looks close to the time it takes the ship to travel her own length, is the signature to act on — well before the roll angle itself becomes alarming.

Following and quartering seas feel, at first, like an easier ride than meeting the weather head-on — the motion is gentler and the apparent wind drops. The danger they carry is different, not smaller. As the encounter frequency falls toward zero — the ship running nearly at the same speed as the waves — she can be picked up and accelerated down the face of a wave, a condition called surf-riding. While surf-riding, the rudder loses much of its bite as the stern lifts clear of solid water and the bow buries, and a ship that starts to yaw off her heading can swing broadside to the sea before the helm can check her — a broach.

Once broached, a ship beam-on in a heavy following sea is exposed to a large, sudden heeling moment from the next crest, at the worst possible angle. The practical defences are set before it gets that far: keep enough speed to retain rudder authority without matching the wave speed closely enough to surf-ride, and choose a heading that avoids running dead before the sea for any length of time when the swell is large and well organised. A moderate alteration of course, taken early, is far cheaper than a large one taken once the stern has already begun to slew.

Whether a ship can be safely berthed without tugs is a planning question, answered before the approach starts, not a test of nerve worked out alongside the jetty. The factors are the same every time: wind and current on the beam, the sequence in which mooring lines can realistically be got ashore and made fast, where the pivot point sits for the manoeuvre being flown, and what thrust is actually available to hold the ship off or bring her alongside once way is off her.

The pivot point matters because it sets the lever arm for everything else: a bow thruster works a long lever arm against the pivot when going ahead and a short one going astern, and the reverse is true of a stern thruster. Wind and current forces, meanwhile, act through the centre of the ship's lateral resistance, not through the pivot — so judging whether the available thrust can hold the ship off is a matter of comparing moments (force × lever arm) about that centre, not comparing raw forces.

When the numbers do not work — thrust and moments too small for the conditions, or the mooring sequence too exposed for the crew available — the honest, professional answer is often to wait for slack water, a wind shift, or a tug, rather than to press an approach the ship is not equipped for on the day.

The recovery manoeuvre itself — Williamson turn, single turn, or Scharnow — is watch- officer knowledge, drilled and largely mechanical once chosen. What sits at management level is everything around it: confirming a reliable datum position and time, starting GMDSS distress alerting and coordinating with other traffic and any SAR authority ashore, allocating the bridge team between conning the ship, keeping visual contact, and running the communications, and — hardest of all — deciding when a search that is not succeeding should be stood down.

• Datum and drift — the search area grows with time and current set from the moment of the fall, so an accurate time and position matter more than a fast start in the wrong direction.
• Coordination, not just execution — command's task is to make sure lookouts, helm, communications and any assisting craft are each doing one job well, rather than to personally manage all of them at once.
• Standing down — a search is eventually ended on a reasoned judgement about survival time in the prevailing water temperature and conditions, weighed against the ship's other duties, not on a fixed clock.

Three scenarios, worked through in full: how much cable an emergency anchoring actually needs to check a ship's way, how to test a following or head sea for parametric-rolling resonance and find a speed clear of it, and how to judge — by comparing moments rather than forces — whether a berthing without tugs is realistic in the wind of the day.