Human Performance and Limitations
Human Performance and Limitations asks how the pilot, not the aeroplane, fails. The syllabus is physiology (hypoxia, decompression, sensory illusions) and psychology (perception, workload, decision-making, CRM). Ghana papers often use short scenarios.
Physiology
- Hypoxia: at FL350 the time of useful consciousness after rapid decompression is roughly 30-60 seconds. Symptoms are insidious - euphoria, poor judgement, cyanosis, tingling.
- Rapid decompression may cause lung barotrauma; oxygen mask on first, then an emergency descent.
- Hyperventilation mimics hypoxia. The distinguishing features are rate and depth of breathing, but oxygen is always the safe first action.
Spatial disorientation
- Somatogravic illusion: linear acceleration is misread as a climb, so a pilot pushes forward during a go-around or after take-off.
- The leans: a slow roll below the vestibular threshold is not sensed, and the correction feels like a bank.
- Coriolis is produced by head movement in a turn; black-hole approach and runway-width illusions distort visual judgement.
Psychology and CRM
- Vision: the fovea needs light for detail; rods dominate at night but are colour-blind and slow to adapt (20-30 minutes dark adaptation). Empty-field myopia and autokinesis affect night approach.
- Fatigue, the circadian low in the early morning, sleep debt and stress degrade vigilance; workload follows the Yerkes-Dodson curve.
- CRM: the SHELL model (Software, Hardware, Environment, Liveware), threat and error management, briefings, cross-check, assertiveness, and the sterile flight deck below 10 000 ft.
Worked example
On a night go-around in rain the aircraft accelerates and the pilot perceives a nose-high attitude, pushing forward. The attitude indicator shows level flight. The correct response is to trust the instruments, cross-check with the other pilot, and fly the flight director. The illusion was somatogravic, caused by linear acceleration, not by real pitch.
Traps
Assuming you will recognise hypoxia in yourself; confusing hyperventilation with hypoxia and delaying oxygen; treating dark adaptation as instant; and believing the ears are reliable in a sustained turn.