Sleep, stress & CRM

040 Human PerformanceChapter 6

Fatigue, stress, and poor crew coordination degrade performance as much as physiology. CRM addresses the human–human interface.

Sleep

Key fact

5 sleep stages — stages 1–4 refresh the body (deep sleep); REM (paradoxical) refreshes the mind. Normal cycle ≈ 90 min; 4–5 REM bouts in 8 hours. Adults need ~8 hours per night.

Key fact

Free-running circadian rhythm ≈ 25 hours. Body temperature lowest ~0500, highest ~1800. Credit/debit system: each hour of sleep ≈ 2 credits, max 16 credits.

Key fact

Jet lag resync: roughly 1–1.5 hours/day westbound, ~1 hour/day eastbound. For 3–4 time zones with 24 h layover — stay in departure country rhythm as long as possible.

Key fact

Alcohol degrades REM sleep. Acute fatigue does NOT have psychological roots (vs chronic stress-related fatigue).

Stress

Key fact

Stress — non-specific body response to demand. Stressor — stimulus interpreted as stressful. Acute stress mobilises resources; chronic stress causes long-term physical/psychosomatic harm.

Key fact

General Adaptation Syndrome: Alarm (↑ glucose, ↓ resistance) → Resistance (fat conversion) → Exhaustion. High arousal narrows attention span — may focus inappropriately.

Key fact

Homeostasis — body maintains stable internal environment (pH 7.2–7.6, temperature ~36.9°C optimum).

Information processing & memory

Key fact

Stages: sensory input → attention → working memory → long-term memory → decision → action. Working memory holds 5–9 items (~7) for ~20 seconds without rehearsal.

Key fact

Long-term memory stores motor programs; affected by expectation and suggestion. Mental rehearsal before performance helps. Environmental capture — skill executed in wrong context (e.g. habit from previous aircraft type).

Key fact

Confirmation bias — seek data supporting your decision. Counter: actively look for disconfirming evidence. Groupthink — unconscious group agreement on a flawed solution.

Decision making & CRM

Key fact

Assertiveness makes crew decision-making most effective. Take as much time as available — time pressure strongly affects analysis. Very high ambition disturbs cooperation climate.

Key fact

CRM improves crew performance through coordination, communication, and shared KSA. Co-action — working in parallel toward one objective. Democratic/co-operative style clarifies conflict causes with all involved.

Key fact

Complacency — unjustified self-confidence. Automation reduces crew attention — risk of being out of the loop; automation errors include capture of wrong sub-program.

Key fact

Invulnerability — “accidents happen to others, not me.” Professional/radio language — limited vocabulary, context gives meaning, quick comprehension.

Operation modes & errors

Key fact

Rasmussen: skill-based (slips), rule-based (rule errors), knowledge-based (technical knowledge errors in novel situations). Anderson: cognitive → associative → automatic learning stages.

Exam trap

Attention — detecting relevant info not in actively monitored channel. Depends on automation level, salience, and expectations.