General: Human Factors in Maintenance
What human factors is about
Human factors studies the relationship between people and the technical and organisational systems they work in. In maintenance it exists because the great majority of occurrences - industry data commonly put it around three-quarters - involve human performance rather than purely technical failure. The aim is not to blame the individual but to design tasks, tools, procedures, training and supervision so that error is less likely and less damaging.
Key frameworks to know: the SHEL model (Software, Hardware, Environment, Liveware - the interface between the human and each of the others is where mismatch causes error), Reason's distinction between active and latent failures, MEDA (Maintenance Error Decision Aid) for investigating maintenance errors, and the Dirty Dozen list of common maintenance error precursors (lack of communication, complacency, lack of knowledge, distraction, lack of teamwork, fatigue, lack of resources, pressure, lack of assertiveness, stress, lack of awareness, norms).
Murphy's law - if anything can go wrong, it will - is not a scientific principle. In exam terms it is a reminder that equipment and people fail in predictable, mundane ways, and that design and checking should assume it.
Traps
Questions often blur human factors with mere carelessness, or imply it only concerns technicians. It applies equally to managers, planners, certifying staff and trainers. Another trap is treating Murphy's law as a physical law.
Rule of thumb: if a task can be done wrong, someone eventually will - so the fix belongs in the system (design, procedure, check), not simply in an instruction to be more careful.