General - Why Human Factors Matters in Maintenance
The starting point
Aircraft are designed and built well, but they are maintained, inspected and certified by people. Analyses of aviation accidents and incidents consistently show that the majority involve human rather than purely technical failure, and maintenance and inspection errors form a significant share of that. Human factors exists to understand those failures and to design the system - tasks, tools, procedures, training, staffing and environment - so that error is less likely and, when it does happen, is caught before it becomes a hazard.
Models a candidate must know
- SHEL model: Software (procedures, manuals, checklists, computer programs), Hardware (aircraft, tools, test equipment), Environment, and Liveware (the people). Liveware sits at the centre; the mismatches at each interface are where error originates.
- Domino theory: an accident is the last domino in a chain; removing any one domino breaks the sequence.
- Reason's Swiss cheese: latent conditions created by management, design or purchasing decisions line up with active failures by front-line staff, and the holes align.
- Heinrich's pyramid: for every serious event there are many minor events and near misses, so near-miss reporting is valuable.
Traps
The commonest is the claim that human factors aims to eliminate human error (impossible) or to find out who was to blame (the opposite of its intent). Another is mislabelling a SHEL interface: a badly written manual is Software–Liveware, not Hardware.
Rule of thumb: when a question asks what should happen after an error, the modern answer is to improve the system and share the lesson - not to punish the individual.