Human Factors: Basic Concepts and Aviation Physiology
Domain 1 tests how human limitations interact with aviation systems, not just isolated physiology facts. Expect questions on the SHELL model, accident causation, error, arousal, and fitness to fly.
Core models
- SHELL: Software, Hardware, Environment and Liveware. The central Liveware matches or mismatches each component; a mismatch at an interface creates error.
- Accidents usually involve latent conditions plus active failures, not one root cause.
- Arousal and stress follow an inverted-U: moderate arousal aids performance; very low arousal causes complacency; very high arousal narrows attention.
- IMSAFE covers Illness, Medication, Stress, Alcohol, Fatigue, Emotion/Eating.
Worked example
An aircraft arrives with a replaced fuel gauge that reads full when the tank is half full. The pilot accepts the reading, plans on full tanks and runs a tank dry. Software (fuel log), hardware (gauge) and Liveware (pilot expectation) are mismatched. The active failure is the planning error, but latent conditions include ambiguous maintenance documentation and schedule pressure. The best answer names the Liveware-hardware/software interface mismatch and the latent conditions, not simply 'pilot carelessness'.
Traps
Do not treat SHELL as a linear chain: every component interfaces with Liveware. Do not label human error as the root cause without asking which interface failed. Arousal is not the same as stress, and high arousal does not always improve performance.