Human Factors (General)
Human factors (general) is the CAA NZ PPL domain that examines how human performance - physiology, perception, decision-making and teamwork - affects flight safety. The exam tests whether you can name the standard models, recognise degraded performance, and apply countermeasures before an error becomes an accident.
Core models
- SHELL: Software, Hardware, Environment and Liveware (the human at the centre). Mismatches at the interfaces - for example, a pilot using an unfamiliar avionics page - are where error arises.
- Dirty Dozen: twelve recurring error precursors including fatigue, complacency, distraction, pressure, lack of communication, lack of teamwork and norms.
- Swiss cheese: defences have holes; an error passes through when holes line up.
- TEM: identify threats, trap errors, manage undesired aircraft states.
- IMSAFE / PAVE / DECIDE are practical preflight and in-flight decision tools.
Physiological limits
Hypoxia is insidious: euphoria and poor judgement appear before headache or cyanosis. Hyperventilation causes dizziness and tingling but is corrected by slowing breathing, not by assuming oxygen is needed. Spatial disorientation - especially in cloud or at night - is countered by trusting instruments, not sensations. Fatigue, dehydration and stress narrow attention and slow checklist use.
Worked example
A pilot with four hours' sleep plans a three-hour VFR flight, feels irritable at preflight, then drifts off track and forgets a fuel check. Reasoning: fatigue is a threat (IMSAFE), and irritability plus missed checks are error signatures. The correct countermeasure is to delay the flight; airborne, simplify tasks, declare reduced capacity and land to reassess - not to push on because the aircraft is serviceable.
Traps
Assuming experience immunises you; treating the Dirty Dozen as a tick-list rather than interacting factors; and confusing hypoxia with hyperventilation. In questions, match the model to the scenario and choose the countermeasure that removes the threat before flight.