Human Performance and Limitations
Human Performance and Limitations tests hypoxia, hyperventilation, spatial disorientation, fatigue, vision, pressurization and CRM. The CPL exam wants recognition and correct first action, not physiology theory for its own sake.
Hypoxia and decompression
Hypoxia symptoms include euphoria, tingling, poor judgement and cyanosis. Time of useful consciousness at FL350 is about 30–60 s; at FL400 about 15–20 s. First action with suspected decompression: oxygen, emergency descent, land as soon as practicable.
Disorientation, vision and fatigue
Spatial disorientation arises when visual cues conflict with vestibular cues; trust instruments. Night vision uses rods and off-centre viewing. Fatigue degrades vigilance and decision-making; circadian low points are early morning and mid-afternoon. CRM uses clear briefings, workload sharing and assertiveness.
Worked example
A pilot at FL380 feels light-headed and euphoric after a pressurization failure. Recognise hypoxia, don the oxygen mask, initiate emergency descent to 10,000 ft or lowest safe altitude, and divert. Do not delay to troubleshoot.
Traps
Confusing hyperventilation with hypoxia; assuming alcohol effects are minor; ignoring CO poisoning; treating fatigue as a motivation issue.