General
The need to take human factors into account; incidents attributable to human factors; Murphy's Law.
General — summary notes
Free- Human factors is the study of how people interact with the tasks, equipment and environment around them — in maintenance, the goal is to design procedures and workplaces that make the correct action the easy action.
- Around 80% of aviation maintenance-related occurrences trace back to human performance, not a mechanical root cause — this is why EASA Part-145 organisations must run a human factors programme.
- "Murphy's Law" — if a component can be fitted incorrectly, sooner or later it will be — is the working assumption behind poka-yoke design: asymmetric connectors, keyed fittings and torque-striping exist because relying on care alone eventually fails.
- Human factors does not mean assigning blame to an individual; it means understanding the conditions (the "error trap") that made the error likely, so the same trap does not catch the next technician.
- ⚠ Exam trap: the SHEL(L) model puts Liveware (the person) at the centre, interfacing with Software, Hardware, Environment and other Liveware — most error occurs at a poor-fitting interface, not from one bad decision.
Two experienced technicians independently cross-connect the same pair of hydraulic lines on the same aircraft type over six months. What does this repetition suggest?
A repeated error by different, competent people points to a systemic error trap (e.g. two identical connectors with no keying) rather than two unrelated individual mistakes — the fix is to redesign the interface (mismatched fittings, colour coding), not to retrain the individuals.
SHELL model
FreeSHELL Model
General quiz
FreeGeneral — quiz
1. What proportion of aviation maintenance occurrences are generally attributed to human factors rather than a purely mechanical cause?
2. "Murphy's Law" as applied to maintenance design means:
3. The primary purpose of a human factors programme in an EASA Part-145 organisation is to:
4. The same wiring error is made independently by three different qualified technicians over a year. This most strongly suggests:
5. "Poka-yoke" design features such as keyed connectors exist to:
6. Human factors as a discipline is primarily concerned with:
7. The SHEL(L) model describes the interfaces between the human and:
8. In the SHEL model, a checklist or work card is part of the: