Human Factors
What you must understand
Human factors is about designing work and environments so that people perform reliably. Know the SHELL model and the error chain concept. Understand perception, attention, memory and decision-making, and how these fail under workload. Study fatigue and circadian rhythm effects on performance, stress, and the difference between acute and chronic stress. Know the physiology of flight: hypoxia, hyperventilation, decompression, spatial disorientation, and the effects of noise and vibration. Understand vision and how lighting affects inspection tasks. Study communication and teamwork, including the importance of clear handover, assertiveness and the use of readback. Know the Dirty Dozen of maintenance errors and the defences against them, plus the principles of a just culture and reporting.
Traps in questions
- Hypoxia symptoms: euphoria and impaired judgement can mask the danger; the sufferer may not recognise it.
- Hyperventilation versus hypoxia: symptoms overlap; the treatment differs.
- Fatigue: chronic fatigue accumulates and is not fixed by one good night's sleep.
- Complacency: often follows routine tasks and familiarity; it is a leading maintenance error.
- Communication: assuming understanding is a classic failure; readback and confirmation are the defences.
Worked example
A technician working a night shift on the third consecutive night is at peak circadian low. Even with adequate total sleep, performance on vigilance tasks is degraded. The defence is not willpower - it is procedural: cross-checking, limiting critical tasks, and using duplicate inspection.
Rule of thumb
When a scenario asks what went wrong, look for the error chain: an unsafe act plus a local trap plus an organisational weakness.