How anchoring control is actually lost on deck — and why it always feels sudden
Category: ON DECK → Deck Machinery
Estimated read time: 55–70 minutes
Audience: Zero knowledge → competent AB → junior officer → senior watchkeeper
Introduction – Why Windlasses Injure Experienced Crew
The windlass is one of the most deceptive machines on deck. It looks slow, deliberate, and mechanically simple. Large steel components move at visible speed, and nothing appears unpredictable. Because of this, crews instinctively treat the windlass as forgiving machinery — something that can be “managed” by feel.
That assumption is wrong.
Windlass accidents are rarely caused by sudden failure. They occur because the brake system is misunderstood, and by the time the misunderstanding becomes visible, the system has already passed the point where human reaction can recover control. When anchoring incidents happen, the most common phrase in reports is that the chain “ran away unexpectedly”. In reality, the loss of control started earlier — quietly, invisibly, and entirely within normal operating behaviour.
To understand windlass safety, you must stop thinking of it as a motor that lowers an anchor and start thinking of it as a machine whose sole purpose is to manage energy.
The Windlass as an Energy-Control System
At its core, a windlass is not designed to stop an anchor. The anchor and chain want to fall under gravity, and the ship itself wants to continue moving through the water. The only thing standing between those forces and uncontrolled motion is friction inside the brake.
The windlass motor does not hold the chain during anchoring. The wildcat does not “grip” it. The brake does all the work — and it does so by converting kinetic energy into heat. Every time the chain moves under load, the brake lining is absorbing energy, heating up, and approaching its design limit.
This is the first concept that must be understood from zero: a windlass brake is not a clamp. It is a consumable energy absorber, and it can be overwhelmed far faster than people expect.
Why Brakes Fail Without Looking Broken
When a windlass brake fails, it almost never snaps, shatters, or visibly breaks. Instead, it fails through thermal degradation. As the chain accelerates, friction generates heat. As heat rises, the coefficient of friction falls. Once the friction drops, the brake must be tightened further to compensate. This additional tightening increases pressure, which increases heat generation even more.
At this point, the system enters a feedback loop. The operator feels the chain speeding up, tightens the brake harder, and unknowingly accelerates the loss of friction. When glazing occurs on the brake lining, the brake does not gradually weaken — it loses effectiveness abruptly. From the operator’s perspective, control appears to vanish “all at once”.
This is why many serious anchoring incidents happen after a brake has apparently worked fine earlier in the operation, or even during the previous anchoring. The damage was done quietly, and the failure only became obvious later.
Letting Go: Where Windlass Control Is Most Commonly Lost
During let-go anchoring, the brake is eased to allow the anchor and chain to run. The assumption many inexperienced crew make is that the brake is either “on” or “off”, and that small adjustments produce small changes. In reality, brake behaviour is non-linear. A tiny change in pressure can produce a large change in chain speed, especially once heat has built up.
The most dangerous moment is not the initial release. It is the moment when the chain appears to slow again and the operator believes control has been regained. This is often the exact point where the brake surface has glazed and effective friction has already been lost. From there, the chain can accelerate beyond any human ability to react.
This is how runaway chain events occur in seconds, even when experienced personnel are present.
Human Positioning Around the Windlass
The windlass creates one of the most dangerous human-machine interfaces on deck. The chain is heavy, irregular, and capable of unpredictable movement. When it runs under load, it stores enormous energy and releases it through vibration, jumping, and recoil.
Most serious injuries occur not because someone was careless, but because they were standing where control felt normal moments earlier. Crossing the chain to reach a control, leaning over the wildcat to observe the run, or standing inline with the chain lead are all behaviours that feel routine until the instant they become fatal.
A critical lesson for new crew is this: you do not move around a windlass when the chain is live. If your position is wrong, the correct response is to stop the operation, not to “step carefully”.
Brake Testing and the Illusion of Security
Brake tests are often misunderstood as proof that the system is safe. In reality, a brake test only shows that the brake can hold under static conditions at a given moment. It does not show how the brake behaves under sustained dynamic loading, heat build-up, or repeated use.
A brake that passes a test in the morning can still fail catastrophically during an anchoring operation in the afternoon. This is not negligence — it is physics. Understanding this distinction is what separates procedural compliance from operational competence.
What Experienced Deck Crew Learn the Hard Way
Experienced deck crew develop a sixth sense around windlasses. They listen to the chain. They feel vibration through the deck. They notice when the sound changes from smooth to uneven. These cues are not superstition — they are early indicators of energy imbalance in the system.
The tragedy is that this knowledge is often acquired only after near-misses. MaritimeHub’s job is to transfer that experience without the injury.
Key Understanding to Carry Forward
Windlass accidents do not come from broken machinery. They come from misunderstanding how friction, heat, and gravity interact. Once control is lost, it cannot be recovered by strength, speed, or experience. The only defence is anticipation and disciplined positioning.