Human Performance and Limitations
What the exam tests
Human performance questions test hypoxia, decompression, fatigue, circadian rhythm, sensory illusions, decision-making and crew resource management. Iran CAO uses ICAO human-factors language, so learn the physiology and the operational countermeasures.
Core rules
- Time of useful consciousness at FL350 is about 30–60 s; at FL400 about 15–20 s. Rapid decompression shortens it.
- Hypoxia signs: euphoria, tingling, visual blur, poor judgement. Hyperventilation causes dizziness and tingling too; the treatment differs.
- Fatigue: circadian low is roughly 02:00–06:00; cumulative sleep debt impairs vigilance more than short-term sleep loss.
- Spatial disorientation: somatogravic illusion during acceleration; leans during prolonged turns; rely on instruments.
- CRM: assertiveness, briefings, callouts, sterile flight deck.
Worked example
A crew reports at 04:00 local for a Tehran departure after a short rest. During climb the captain feels 'everything is fine' but the first officer notes a slow drift above cleared level. The captain's euphoria is a hypoxia/fatigue red flag, not proof of fitness. The correct action is to don masks, confirm cabin altitude, descend to 10,000 ft or MSA, and hand control to the monitoring pilot. Reasoning: at circadian low, self-assessment is unreliable; the other crew member's cross-check is the safety barrier.
Traps
Treating hyperventilation with more oxygen without considering hypoxia; ignoring cabin altitude because the mask is on; confusing somatogravic illusion with a real climb; assuming 'I feel fine' means normoxia; using caffeine as a fatigue cure.