Module
Human Error and Error Management
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Understanding Human Error
Error is a normal and inevitable part of human performance. Despite our best intentions and training, all humans make errors. The key insight from Human Factors is that errors are not moral failings — they are symptoms of deeper system issues.
A modern view of error recognises that:
- Errors are caused by system factors, not just individual carelessness
- Blaming individuals does not prevent future errors
- Understanding why errors occur is essential for prevention
- Systems should be designed to be resilient to error
The aviation industry has learned that the most effective way to improve safety is not to punish people for making errors, but to understand the conditions that lead to errors and design systems that prevent or catch them before they cause harm.
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Types of Human Error
Human errors can be categorised into four main types:
1. Slips: Actions that do not go as planned. You intend to do the right thing but your execution is wrong. Example: reaching for the wrong switch.
2. Lapses: Memory failures. You forget to do something you intended to do. Example: forgetting to complete a checklist item.
3. Mistakes: Planning failures. You do the wrong thing because your understanding or plan was incorrect. Example: setting the wrong altimeter reading because you misunderstood the procedure.
4. Violations: Deliberate deviations from rules or procedures. These may be motivated by time pressure, convenience, or a belief that the rule is unnecessary.
Understanding the type of error is important because each type has different causes and requires different prevention strategies. Slips and lapses are best prevented through design changes, while mistakes require better training and procedures.
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The Swiss Cheese Model
James Reason's Swiss Cheese Model is a powerful metaphor for how accidents occur in complex systems.
The model depicts layers of defence (cheese slices) between hazards and accidents. Each layer has holes (weaknesses) that vary in size and position. For an accident to occur, the holes in all layers must align, allowing a trajectory of opportunity.
In aviation, defensive layers include:
- Training and licensing
- Procedures and checklists
- Design features and automation
- Supervision and oversight
- Regulatory requirements
The Swiss Cheese Model illustrates why accidents rarely have a single cause. Multiple failures across different layers must align for an accident to occur. This is why effective safety improvement requires addressing multiple layers simultaneously, not just focusing on the last error before the accident.
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Error Management and Just Culture
Error management recognises that since errors cannot be eliminated, the goal is to:
- Prevent errors where possible
- Detect and correct errors before they cause harm
- Mitigate the consequences of errors that are not caught
- Learn from errors to improve the system
Just Culture is a key concept in error management. It strikes a balance between:
- Blame-free culture (where all errors are tolerated)
- Punitive culture (where all errors are punished)
In a Just Culture:
- Unintentional errors are treated as learning opportunities
- At-risk behaviours are addressed through coaching
- Reckless behaviours are subject to disciplinary action
- Reporting errors is encouraged and protected
This approach encourages open reporting of errors and near-misses, which is essential for learning and improvement. Without a Just Culture, people hide their errors, and the organisation cannot learn from them.
quiz
End of Module Check
Quiz: 7 questions
What is a slip?
- AA memory failure
- BAn action that does not go as planned
- CA planning failure
- DA deliberate rule violation
What does the Swiss Cheese Model illustrate?
- AHow cheese is produced
- BHow multiple defensive layers must fail for an accident to occur
- CHow to stack safety procedures
- DHow regulations are layered
In a Just Culture, how are unintentional errors typically handled?
- AWith disciplinary action
- BAs learning opportunities
- CWith financial penalties
- DThey are ignored
What is a violation?
- AA skill-based error
- BA deliberate deviation from rules
- CA memory failure
- DA misunderstanding of procedures
What is the primary goal of error management?
- AEliminate all errors
- BCreate systems resilient to error
- CPunish those who make errors
- DIncrease automation
Why is open error reporting important?
- AIt allows organisations to learn and improve
- BIt helps identify who to blame
- CIt satisfies regulatory requirements
- DIt reduces paperwork
Which type of error involves doing the wrong thing due to a flawed plan?
- ASlip
- BLapse
- CMistake
- DViolation
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