Why “the computer says OK” is not a defence
Contents
Use the links below to jump to any section:
- Introduction – Why This Article Matters
- What a Loading Computer Actually Is
- What the Loading Computer Calculates
- What the Loading Computer Does Not Know
- Input Data – Where Most Errors Begin
- Assumptions Hidden Inside the Software
- Approval Criteria vs Real Safety
- Sequence Matters – Static Results vs Dynamic Reality
- Loading Computers During Cargo Operations
- When the Computer Is Right but the Ship Is Not
- Legal and Professional Responsibility
- Professional Use of Loading Computers
- Closing Perspective
- Knowledge Check – Loading Computers
- Knowledge Check – Model Answers
1. Introduction – Why This Article Matters
Loading computers have prevented countless accidents — and contributed to many others.
They are powerful, precise, and persuasive. They present numbers, curves, and green indicators that imply certainty. This makes them one of the most dangerous tools on board when misunderstood.
A loading computer does not make a ship safe.
It only describes a condition — assuming the inputs are correct.
2. What a Loading Computer Actually Is
A loading computer is a numerical model of the ship, built from hydrostatic data, stability criteria, and structural limits.
It does not “measure” the ship.
It calculates what the ship should be doing — based on what it is told.
The computer has no awareness of:
- how cargo was actually placed
- whether tanks contain what you think they do
- whether drafts were read correctly
It trusts the user completely.
3. What the Loading Computer Calculates
Depending on ship type and software, loading computers typically calculate:
- displacement and drafts
- trim and list
- centre of gravity position
- GM and righting levers (GZ)
- compliance with statutory stability criteria
- structural limits (bending moments, shear forces)
These outputs are conditional — they are only as good as the data that created them.
4. What the Loading Computer Does Not Know
The loading computer does not know:
- if cargo weights are accurate
- if density assumptions are correct
- if tanks contain residue or sediment
- if drafts were affected by swell
- if free surface is worse than assumed
The computer cannot question you.
This asymmetry is dangerous:
the user can be wrong, but the computer will still produce confident results.
5. Input Data – Where Most Errors Begin
Nearly all loading-computer-related incidents trace back to input errors.
Common sources include:
- incorrect cargo weights
- wrong tank soundings
- assumed instead of measured densities
- failure to account for slack tanks
- copying previous voyage data
Once an incorrect assumption enters the model, every output becomes misleading — yet internally consistent.
This is why wrong results often look “perfect”.
6. Assumptions Hidden Inside the Software
Loading computers rely on assumptions that are often forgotten once installed.
These include:
- intact hull condition
- even distribution within holds
- no cargo shift
- no progressive flooding
- calm-water hydrostatics
The moment real conditions violate these assumptions, results diverge from reality — silently.
The software does not warn you that assumptions are no longer valid.
7. Approval Criteria vs Real Safety
Passing stability criteria does not guarantee safety.
Criteria define minimum acceptable behaviour, not operational margin. They do not account for:
- heavy weather
- long-term fatigue
- human error
- cargo securing failures
Many ships that capsized or lost cargo were technically compliant at departure.
Compliance is a floor, not a shield.
8. Sequence Matters – Static Results vs Dynamic Reality
Loading computers usually present final conditions.
However, ships fail during intermediate stages:
- partial loading
- tank transfers
- ballast lag
- trim transitions
A condition that is safe at completion may pass through unsafe states during the sequence.
Professional operators model sequences — not just endpoints.
9. Loading Computers During Cargo Operations
During cargo operations, stability changes minute by minute.
Professional practice includes:
- updating inputs continuously
- monitoring transient conditions
- coordinating ballast proactively
- verifying drafts independently
The loading computer must be actively managed, not consulted occasionally.
10. When the Computer Is Right but the Ship Is Not
Some of the most serious incidents occur when:
- the computer is correct
- the inputs are wrong
- the ship behaves unexpectedly
This creates dangerous cognitive conflict: officers trust the screen more than their senses.
When reality and software disagree, reality always wins — but often too late.
11. Legal and Professional Responsibility
From a legal perspective, loading computers do not carry responsibility.
The Master does.
Investigations consistently conclude:
“The Master relied on the loading computer output.”
Reliance is not defence.
Understanding is expectation.
12. Professional Use of Loading Computers
Professional officers treat loading computers as:
- verification tools
- scenario testers
- trend monitors
They cross-check with:
- drafts
- experience
- expected behaviour
- physical intuition
They never abdicate judgement to software.
13. Closing Perspective
A loading computer is a powerful mirror.
It reflects exactly what you tell it — no more, no less.
If you feed it assumptions, it will give you confidence.
If you feed it reality, it will give you insight.
The danger is not trusting computers.
The danger is forgetting who is responsible for the ship.
14. Knowledge Check – Loading Computers
- What is a loading computer fundamentally modelling?
- Why does a loading computer never “measure” the ship?
- Which part of the system carries the highest error risk?
- Why can incorrect inputs still produce compliant outputs?
- What assumptions are built into loading computer models?
- Why does compliance not equal safety?
- Why are intermediate loading stages dangerous?
- What happens when ship behaviour contradicts software output?
- Who is legally responsible for stability decisions?
- How should loading computers be used professionally?
15. Knowledge Check – Model Answers
- A numerical model of the ship’s hydrostatics and stability.
- Because it relies entirely on user-provided data.
- Data input by humans.
- Because the software is internally consistent.
- Intact hull, correct data, calm water, no cargo shift.
- Because criteria define minimum performance, not margin.
- Because stability passes through transient unsafe states.
- Reality must override software immediately.
- The Master.
- As decision aids, not decision makers.