Human Performance
The body in the air
Human performance questions test physiology and psychology in equal measure. Physiology: respiration and hypoxia, hyperventilation, decompression and time of useful consciousness, cabin altitude and oxygen rules, vision (rods and cones, night blind spot, dark adaptation), hearing, spatial disorientation and the classic illusions - somatogravic, somatogyral, the leans, black-hole approach and false horizon. Psychology: information processing, attention, workload, fatigue and circadian rhythm, stress, personality, crew resource management, communication, leadership, and error models such as SHELL and the Swiss cheese model.
Traps
Hypoxia and hyperventilation present similarly, but hyperventilation improves with slower breathing while hypoxia does not. Time of useful consciousness falls sharply with altitude: roughly 3 to 5 minutes at FL250, 1 to 2 minutes at FL300 and 30 to 60 seconds at FL350. Carbon monoxide poisoning is insidious - headache and confusion without cyanosis. Questions describing a pilot who 'did not notice' usually point to expectation bias or inattentional blindness rather than incompetence.
Worked example
A pilot at FL350 suffers a loss of pressurization. Oxygen mask on first, then emergency descent. At FL350 the useful consciousness window is only about 30 to 60 seconds, so the mask must be donned before analysing the checklist.