Human Performance and Limitations
Human Performance and Limitations tests how the pilot's body and mind cope with altitude, workload, fatigue, sensory illusions and team communication. Questions are applied: what happens, why, and what to do.
Hypoxia and hyperventilation
- Hypoxia reduces oxygen to the brain; symptoms include euphoria, tingling, poor judgement and cyanosis.
- Time of useful consciousness at FL350 is roughly 30–60 seconds; at FL400 it is 15–20 seconds.
- Above 10,000 ft, supplemental oxygen is needed; above FL250, masks must be available and above FL300 one pilot must be on oxygen.
Spatial disorientation and CRM
- Somatogravic illusion makes acceleration feel like a climb; deceleration feels like a descent.
- The leans, graveyard spiral and Coriolis illusion are vestibular illusions; trust the instruments.
- CRM uses briefings, callouts, workload sharing and assertiveness to catch errors.
Worked example
A rapid decompression occurs at FL380. The pilot has perhaps 15–20 seconds of useful consciousness. The correct first action is to don the oxygen mask and establish communications; descending to FL100 follows once the mask is on and the situation is under control. Trying to diagnose the problem first risks incapacitation.
Traps that cost marks
- Treating hyperventilation and hypoxia as the same; hyperventilation causes dizziness and tingling but improves with slower breathing.
- Believing you can overcome spatial disorientation by feel.
- Forgetting that fatigue and stress degrade radio phraseology and checklist discipline.