Human Performance and Limitations
Core concepts
Candidates must understand the senses used in flight (vision, hearing, balance), hypoxia and hyperventilation, spatial disorientation and illusions, fatigue and circadian rhythm, stress and workload, decision-making models, and the effects of alcohol, medication and carbon monoxide. Know the difference between the types of hypoxia and their causes, and the role of the vestibular system in creating false sensations.
Traps
Questions exploit confusions: hyperventilation and hypoxia share symptoms but have opposite carbon dioxide states; somatogravic illusion occurs with linear acceleration, not rotation; the leans arise from a subtle bank; blackout versus redout depends on G direction. Be careful with "the most dangerous" phrasing: fatigue and complacency are frequently cited. Also know that night vision relies on rods and is degraded by smoking, altitude and bright light.
Worked example
In a prolonged climb without oxygen above 10,000 ft, a pilot feels euphoric and makes errors. Rule of thumb: treat any unexplained well-being, tingling or poor judgment as possible hypoxia and descend or use oxygen immediately. Time of useful consciousness falls rapidly with altitude, so act before symptoms become disabling.
Exam technique
Match the symptom to the physiological cause, then choose the corrective action. Prefer answers that restore oxygen or reduce workload over those that merely "try harder".