Human Performance and Limitations
Human Performance and Limitations examines how the pilot's body, senses and decision-making affect flight safety. The exam tests recognition of hypoxia, hyperventilation, spatial disorientation, visual illusions, fatigue, stress, alcohol and medication, plus crew resource management in single-pilot operations.
Physiological threats
- Hypoxia reduces oxygen to the brain. Early signs include euphoria, poor judgement, headache and impaired vision; the pilot may not notice the deterioration. Oxygen requirements depend on cabin altitude and duration.
- Hyperventilation causes dizziness, tingling and anxiety and can mimic hypoxia. Rapid breathing must be controlled; do not assume every symptom is hypoxia.
- Spatial disorientation arises when the vestibular system gives false motion cues. Somatogravic illusion during acceleration feels like a pitch-up; somatogyral illusion can persist after a turn.
- Visual illusions include the black-hole approach, where a lack of ground cues makes the aircraft seem high; runway width and slope also distort the approach.
Fatigue, stress and fitness
- Fatigue slows reaction time, reduces situational awareness and increases fixation. Rest before flight is more effective than caffeine.
- Alcohol impairs judgement and coordination; effects persist after the blood alcohol level falls. Medication and drugs must be assessed for flight safety, and the pilot must not fly when unfit.
- Stress can narrow attention; use decision models and checklists to restore structure. In single-pilot operations, CRM means managing automation, passengers and workload as resources.
Worked example
On a go-around in a high-performance light aircraft, the pilot experiences strong forward acceleration. The otolith organs signal a false pitch-up, and the pilot may push forward to 'correct' it. The correct response is to trust the attitude indicator and established pitch/power targets, not the seat-of-the-pants sensation. This is the somatogravic illusion.
Traps that cost marks
Do not treat hyperventilation as proof of hypoxia; symptoms overlap. Do not assume you will feel hypoxic warning signs reliably. Do not rely on 'fresh air' to cure fatigue. Alcohol and dehydration worsen spatial disorientation. A passenger who is anxious can distract the pilot; brief them and use a sterile-cockpit discipline.
Key points
- Hypoxia impairs judgement early; symptoms are unreliable and may include euphoria.
- Hyperventilation can mimic hypoxia; control breathing and cross-check.
- Somatogravic illusion during acceleration causes a false pitch-up sensation.
- Black-hole approach makes the aircraft appear high; use instruments and glidepath guidance.
- Fatigue, alcohol and medication degrade judgement and situational awareness.
- Single-pilot CRM includes task prioritisation, passenger management and use of automation.