Human Performance and Limitations
Human Performance and Limitations tests the pilot's physiology, sensory limitations and decision-making under workload.
Oxygen and pressure
- Hypoxia types: hypoxic, anaemic, stagnant and histotoxic. At 18,000 ft useful consciousness is about 20–30 minutes; after rapid decompression at FL350 it is 30–60 seconds.
- Hyperventilation causes dizziness, tingling and cramps; hypoxia can mimic it. Use oxygen and controlled breathing.
- Decompression: don oxygen first, then descend; avoid holding breath during rapid decompression.
Sensory and cognition
- Vision: rods for night, cones for colour; dark adaptation takes about 30 minutes. Avoid bright light before night flight.
- Spatial disorientation: somatogravic illusion in acceleration, black-hole approach and leans. Trust instruments.
- Fatigue and circadian rhythm: duty limits, sleep debt and the window of circadian low all degrade performance.
Human error and CRM
- SHELL model: Software, Hardware, Environment and Liveware. Reason's Swiss cheese model separates latent and active failures.
- Decision making: gather information, assess risk, choose, act and review. Use callouts and cross-checking.
Worked example
On a night approach over dark terrain, a pilot feels a pitch-up illusion after acceleration. The correct response is to cross-check the attitude indicator and altimeter, not to push based on sensation. The somatogravic illusion is caused by linear acceleration stimulating the otoliths.
Traps
- Treating hyperventilation as hypoxia and giving oxygen without reassessing.
- Assuming dark adaptation is immediate.
- Relying on feel in IMC.