Human Performance and Limitations
What the exam tests
This domain tests how hypoxia, fatigue, stress, illusions, vision and decision-making affect pilot performance, and whether you can choose the correct recovery action.
Core rules
- Hypoxia reduces oxygen to the brain; early signs include euphoria, impaired judgement and tingling. Correct action is to use oxygen and descend. Hyperventilation produces dizziness and tingling but improves with controlled breathing and reassurance.
- Spatial disorientation occurs when vestibular illusions conflict with instruments. In cloud or at night, trust the instruments and maintain a stable attitude.
- The black-hole approach makes a normal approach seem too high, leading to a low approach. Use visual glide slope aids or instruments.
- Fatigue, dehydration and stress narrow attention and slow decision-making. Alcohol, drugs and some medications are incompatible with flying.
- Good airmanship uses briefings, checklists, sterile cockpit rules and an early decision to go around or divert.
Worked example
On a dark night with no ground lights, the runway appears higher than it is, so the pilot flies a low approach. The correct reasoning is that the illusion affects visual height judgement, not the aircraft. The pilot should fly the published approach path or use the PAPI/ILS, and go around if the approach is unstable.
Traps
Treating hyperventilation as hypoxia and giving oxygen without controlling breathing; believing instruments during a somatogravic illusion; pressing on with get-there-itis; and ignoring the effects of mild dehydration or fatigue.