Human Performance and Limitations
The body in flight
Understand hypoxia, hyperventilation, decompression, acceleration, barotrauma, decompression sickness, carbon monoxide poisoning, noise and vibration. Know the time of useful consciousness falls rapidly with altitude and that hypoxia and hyperventilation share symptoms - dizziness, tingling, confusion - so the response is to use oxygen and descend, not to diagnose on the fly. Vision questions cover rods and cones, dark adaptation, the off-centre scan at night, and the black-hole approach illusion.
Orientation, fatigue and decision-making
Spatial disorientation arises when vestibular cues conflict with instruments; the somatogravic illusion during acceleration feels like a climb, and the leans and Coriolis illusions can be powerful. Fatigue is cumulative, circadian rhythms affect alertness, and stress narrows attention. Know the SHELL model, the Reason Swiss-cheese model, threat and error management, and the importance of closed-loop communication and assertiveness in CRM.
Worked example
At FL350, useful consciousness after rapid decompression is roughly 30–60 seconds. The correct priority is to don oxygen immediately, establish a descent, and only then communicate. At FL400 the window is shorter still - about 15–20 seconds.
Rule of thumb
Aviate, navigate, communicate - and at high altitude, oxygen first. Never accept “I feel fine” as evidence of adequate oxygenation; hypoxia impairs the judgement needed to recognise it.