Human Performance and Limitations
Core framework
This domain links physiology and psychology to flight safety. Understand hypoxia, hyperventilation, spatial disorientation, the vestibular system (semicircular canals and otolith organs), and the effects of fatigue, stress and workload on decision-making.
Concepts to master
Hypoxia types (hypoxic, hypemic, stagnant, histotoxic) and their signs. Hyperventilation mimics hypoxia - the treatment differs: slow the breathing rate. Spatial disorientation arises because the vestibular system cannot distinguish acceleration from gravity in the absence of visual references; illusions include the somatogravic and somatogyral effects. Recognise fatigue (acute vs chronic) and the importance of crew rest. Understand the SHELL model and the error chain.
Traps
- Treating hyperventilation as hypoxia and giving oxygen when the correct first action is to control breathing.
- Confusing the semicircular canals (angular acceleration) with the otolith organs (linear acceleration/gravity).
- Assuming you can "fly by the seat of your pants" in IMC - you cannot.
- Mixing acute fatigue (recent) with chronic fatigue (cumulative).
Rule of thumb
"If in doubt in IMC, trust the instruments, not your body." Vestibular illusions are strongest during acceleration, turns and head movements.
Worked example
A pilot in cloud feels a false climb sensation after acceleration. The somatogravic illusion makes acceleration feel like a pitch-up. Correct response: cross-check the attitude indicator and maintain instrument scan.