ATPL Human Performance cheat sheet

Human factors studies the fit between people, machines and the operating environment; the SHEL model separates Software, Hardware, Environment and Liveware, with the central Liveware block representing the pilot interfacing with all others.

The 'dirty dozen' error precursors include fatigue, complacency, distraction, lack of communication, lack of teamwork, lack of resources, pressure, lack of assertiveness, stress, lack of awareness, norms and lack of knowledge.

Reason's Swiss cheese model: accidents occur when latent conditions in organisational layers line up with active failures at the sharp end; defences are layers with holes that move.

SHELL edges must be matched: L-S, L-H, L-E and L-L mismatches are where errors arise; L-L (crew interaction) mismatches are the most frequent in aviation.

Latent failures are decisions or conditions made by designers, managers and regulators whose effects are delayed and distant from the accident; active failures are unsafe acts by front-line operators.

Murphy's law and the 'law of least effort' describe humans tending to take the easiest path; ergonomic design should make the correct action the easiest action.

Flight deck automation changes the human role from manipulator to monitor; this increases vigilance demands and risk of complacency and skill decay.

ICAO Annex 1 and PANS-TRG frame human performance as a required competency; CRM, TEM and HF training are mandated elements of type training.

Dalton's law: total pressure is the sum of partial pressures; at altitude, alveolar PO2 falls even though the percentage of oxygen in air stays 21%.

Hypoxia types: hypoxic (reduced alveolar PO2), hypaemic (anaemia/CO poisoning), stagnant (G-forces, heart failure), histotoxic (alcohol, cyanide).

Time of useful consciousness without oxygen: about 15-20 s at FL500, 30-60 s at FL430, 1-2 min at FL400, 2-3 min at FL350, 5-10 min at FL300.

Cabin altitude above 10,000 ft requires crew oxygen; above 14,000 ft continuous use; a rapid decompression above FL250 demands immediate 100% oxygen and emergency descent.

Decompression sickness: nitrogen bubbles form when ambient pressure falls too fast after saturation at higher pressure; avoid flying within 12-24 h after diving (longer after multiple dives).

Barotrauma: middle-ear and sinus blocks occur when the Eustachian tube or sinus ostia cannot equalise; treat with Valsalva or Frenzel, decongestants, and do not fly with a severe cold.

Hyperventilation lowers CO2, causing cerebral vasoconstriction, dizziness, tingling and tetany; treat by controlled breathing and, if in doubt with hypoxia, give 100% oxygen.

Vision: scotopic (rod) vision needs 20-30 min dark adaptation and is poor for detail; colour vision uses cones concentrated in the fovea; empty-field myopia occurs over featureless terrain or water.

Spatial disorientation: somatogyral illusion (post-rotation), somatogravic illusion (acceleration feels like pitch-up), and leans follow sustained false references; trust instruments over sensations.

Maslow's hierarchy: physiological, safety, social, esteem, self-actualisation; lower needs dominate attention until satisfied.

Pilot personality traits associated with safety: self-confidence, need for achievement, conscientiousness, low impulsivity, high stress tolerance; hazardous attitudes include macho, impulsivity, invulnerability, resignation and anti-authority.

Perception is influenced by expectation, motivation, emotion and prior experience; expectation bias causes pilots to 'see' what they expect on the flight deck.

Attention is limited; vigilance decrements after 20-30 min on monotonous monitoring tasks; task shedding occurs under high workload (prioritise aviate, navigate, communicate).

Arousal follows the Yerkes-Dodson inverted U: performance peaks at moderate arousal; low arousal causes boredom errors, high arousal causes narrowing of attention and fixation.

Memory: sensory store <1 s, short-term/working memory 15-30 s with capacity 7±2 chunks, long-term memory effectively unlimited; chunking and rehearsal aid retention.

Motivation can be intrinsic or extrinsic; over-motivation increases anxiety and error rate; habit interference occurs when a well-learned response is inappropriate to the new situation.

Stereotype and halo effects bias assessment of others; groupthink in crews suppresses dissent and reduces safety margins.

Error types: slips (correct intention, wrong execution), lapses (memory failures), mistakes (wrong intention: rule-based or knowledge-based), and violations (deliberate deviations).

Reason's classification: unintended actions (slips, lapses) versus intended actions (mistakes, violations); violations are routine, exceptional or acts of desperation.

Error management has three layers: prevention (reduce opportunity), trapping (detect before consequence) and tolerance (reduce consequence after error).

Reliability: human error rate for simple well-practised tasks is about 1 in 1,000; for complex novel tasks it can be 1 in 10 or worse; error rates rise sharply under stress and fatigue.

Error-provoking conditions (preconditions): fatigue, high workload, time pressure, poor communication, inadequate equipment, ambiguous procedures and lack of feedback.

Just culture distinguishes human error (console), at-risk behaviour (coach) and reckless behaviour (punish); the aim is to encourage reporting without removing accountability.

Threat and Error Management (TEM): threats are external events, errors are crew actions, undesired aircraft states are the result; countermeasures are trap, avoid, correct.

Normalisation of deviance: repeated small deviations become accepted practice until an accident exposes the drift; audits and FOQA data detect drift.

Sensation is the detection of stimuli by receptors; perception is the interpretation of those stimuli using expectation, memory and context.

Signal detection theory: detection depends on signal strength and the criterion (response bias); a liberal criterion raises hits but also false alarms.

Thresholds: absolute threshold is the minimum detectable stimulus; difference threshold follows Weber's law (just-noticeable difference proportional to stimulus intensity).

Perception is subject to constancies, illusions and closure; the Gestalt principles (proximity, similarity, closure, continuity) explain grouping and can mislead.

Working memory holds about 7±2 items for 15-30 s; cognitive load theory says reduce extraneous load (clutter, unclear displays) and build schemas through practice.

Mental models and schemas guide interpretation; when the actual situation diverges from the model, confirmation bias keeps pilots locked onto the wrong hypothesis.

Decision-making under uncertainty uses heuristics (availability, representativeness, anchoring) that are fast but biased; checklists and cross-checks compensate.

Automation and monitoring: humans are poor vigilance monitors; automated systems create complacency, mode confusion and out-of-the-loop performance problems.

Standard phraseology reduces ambiguity; readback of clearances is mandatory and the readback must be verified by the issuing controller.

Closed-loop communication: sender transmits, receiver repeats back, sender confirms; this detects and corrects transmission errors.

Barriers to communication: noise, high workload, authority gradient, cultural differences, fatigue, non-standard phraseology and expectation bias.

Effective briefing: brief threats, terrain, weather, NOTAMs and division of duties; briefs should be short, specific and interactive.

Assertiveness: use graded levels (hint, preference, suggestion, emergency) and the PACE model (Probe, Alert, Challenge, Emergency) when a concern is not addressed.

Crew coordination: clear role assignment (PF/PM), sterile flight deck below 10,000 ft, standard callouts and challenge-response checklists.

Assertiveness and authority gradient: steep gradients suppress junior input; flat gradients can cause confusion; the optimum is a consultative gradient.

Handover: use structured formats (SBAR: Situation, Background, Assessment, Recommendation) and confirm understanding; avoid abbreviated informal handovers.

Decision-making models: analytical (DECIDE: Detect, Estimate, Choose, Identify, Do, Evaluate) and naturalistic (recognition-primed) for experienced pilots in time-critical situations.

DECIDE: Detect change, Estimate need to react, Choose outcome, Identify actions, Do action, Evaluate result.

Recognition-primed decision making (Klein): experts recognise a familiar pattern, choose the first workable option and mentally simulate it; risk is applying a familiar but wrong pattern.

Heuristics and biases: confirmation bias, anchoring, availability, framing, sunk-cost and plan-continuation bias all increase risk of continuing an unsafe course.

Crew resource management decision aids: FOR-DEC (Facts, Options, Risks, Decision, Execution, Check) for structured crew decisions.

Risk assessment: use a matrix of severity × probability; risk is acceptable only when mitigation reduces it to an agreed tolerable level.

Decision traps: get-there-itis, plan continuation, pressure from passengers or schedule, and escalation of commitment to a chosen plan.

Decision quality improves with briefing, cross-checking, using all available information, and a deliberate 'what could go wrong' step.

Circadian rhythm is a roughly 24-hour internal clock controlled by the suprachiasmatic nucleus; core body temperature minimum occurs around 03:00-05:00 local, when alertness is lowest.

Sleep architecture: NREM stages N1-N3 and REM; N3 (slow-wave) restores the body, REM restores cognition and memory; both are needed for full recovery.

Sleep debt accumulates with each short sleep and is only repaid by sleep, not by caffeine or motivation; chronic restriction degrades performance before subjective awareness.

Fatigue effects: slowed reaction time, narrowed attention, impaired working memory, increased variability and microsleeps; performance at 24 h awake resembles 0.10% blood alcohol.

Circadian desynchrony (jet lag) occurs with rapid time-zone crossing; eastward travel is generally harder than westward; adaptation takes about 1 day per time zone.

Countermeasures: strategic napping (20-40 min or 90 min), controlled rest on the flight deck where permitted, caffeine timing, light exposure and proper layover sleep.

WOCL (window of circadian low) is about 02:00-06:00; fatigue risk is highest on early starts, night flights and the second consecutive night.

Sleep inertia: grogginess for 15-30 min after waking from slow-wave sleep; allow time before critical tasks and avoid long naps close to duty.

Stress is the non-specific response of the body to any demand; eustress (positive) improves performance, distress (negative) impairs it.

General adaptation syndrome (Selye): alarm, resistance and exhaustion stages; prolonged stress depletes coping resources.

Acute stress symptoms: increased heart rate, rapid breathing, sweating, narrowed attention, impaired judgement and memory; chronic stress causes sleep disturbance, irritability and health problems.

Coping strategies: problem-focused (change the situation) and emotion-focused (change the response); both are valid, but avoidance coping is maladaptive.

Stressors: environmental (noise, vibration, temperature), physiological (fatigue, illness), psychological (workload, responsibility) and social (interpersonal conflict).

Arousal and performance: Yerkes-Dodson inverted U; moderate arousal optimises performance; extreme arousal causes freezing, hypervigilance and error.

Crew resource management reduces stress through briefing, workload sharing, cross-checking and speaking up; isolation increases stress.

Stress management techniques: controlled breathing, progressive muscle relaxation, physical exercise, adequate sleep, social support and debriefing.