ATPL Human Factors (CAA) cheat sheet

Human Factors definition (ICAO): the study of human capabilities, limitations and behaviour and their interaction with the aviation system; aims at safety and efficiency, not at 'fixing' pilots.

SHEL model: Software, Hardware, Environment, Liveware; the mismatches at the L-H interface (and L-S, L-Hard, L-Env) are where errors concentrate; the central Liveware is the pilot.

Reason's '4 Ms' of error sources: Man, Machine, Medium (environment), Management (organisation); errors arise from mismatches, not from individual blame.

Dirty Dozen (12 error precursors): fatigue, complacency, lack of knowledge, distraction, lack of teamwork, lack of resources, pressure, lack of assertiveness, stress, lack of awareness, norms, lack of communication.

Murphy's law for aviation: if something can be done wrong, eventually it will be; design and procedures must make correct action easier than incorrect action.

Swiss cheese model: accidents occur when holes in defensive layers (organisational, supervisory, preconditions, unsafe acts) line up; defences, not blame, are the target.

Pilot's role in safety: the human is both the most flexible and the least reliable component; ~70-80% of accidents have a human-factors component.

Aviation psychology vs physiology: psychology covers perception, memory, decision-making and error; physiology covers hypoxia, vision, hearing, decompression and fatigue.

Hypoxia: at 10,000 ft (3,000 m) arterial O2 saturation ~90%; at 18,000 ft (5,500 m) ~70%; at 22,000 ft (6,700 m) ~60% - time of useful consciousness drops to minutes.

Time of useful consciousness (TUC), no oxygen: ~10 min at FL250, ~3-5 min at FL300, ~1.5-3 min at FL350, ~15-20 s at FL430.

Hyperventilation vs hypoxia: hyperventilation gives tingling, dizziness, muscle spasm; treat by slowing breathing and rebreathing; hypoxia is treated by 100% O2 and descent.

Decompression: slow decompression can be silent; explosive decompression causes fog, temperature drop and noise; immediate action: O2 mask, seat belt, descend to 10,000 ft.

Barotrauma: pain on descent due to blocked Eustachian tube; treat with Valsalva or Toynbee manoeuvre; never fly with a cold or ear infection.

Vision: rods for night vision (peripheral, slow dark adaptation ~30 min), cones for colour and acuity (fovea); avoid bright light before night flight and use off-centre viewing.

Spatial disorientation: vestibular system can mislead in IMC; rely on instruments; illusions include somatogravic (false climb on acceleration), leans, and Coriolis.

Carbon monoxide: binds haemoglobin ~200-250 times more strongly than O2; symptoms include headache, nausea, cherry-red skin; treat with 100% O2 and descent.

DCS: nitrogen bubbles after rapid decompression; symptoms include joint pain, skin mottling, neurological signs; treat with 100% O2 and descent to sea level; avoid flying after diving.

Information processing model: sensation → perception → decision → response; limited channel capacity means overload causes omissions and errors.

Attention: selective (focus on one source), divided (simultaneous tasks), and vigilance (sustained) - vigilance declines after ~30 min; avoid monotony with active monitoring.

Perception is top-down: expectations bias interpretation; a pilot may 'see' what they expect, not what is there; use cross-checks and confirmations.

Working memory: limited to ~7 ± 2 items, short duration (~20-30 s); use written clearances, checklists and read-back to offload.

Long-term memory: procedural (skills), declarative (facts), episodic (events); retrieval is cue-dependent; checklists are external memory aids.

Memory errors: forgetting, misremembering, and 'false memory'; prospective memory (remembering to do something later) is fragile under load.

Sensory memory: iconic (visual, ~0.5 s) and echoic (auditory, ~2-4 s); echoic allows a brief 'replay' of a clearance, but not reliable for long messages.

Perception illusions: black-hole approach (night, no visual horizon), runway width illusion, and size-distance illusions; use instrument references and PAPI/ VASI.

Reason's model: unsafe acts = errors (slips, lapses, mistakes) + violations; latent conditions in organisation + active failures at front line.

Slip: correct intention, wrong execution (e.g., wrong switch); lapse: forgotten action; mistake: wrong intention (rule-based or knowledge-based); violation: deliberate deviation.

Error management: prevention (reduce error), detection (catch it), and recovery (limit consequences); TEM adds threats as a third element.

Threat and Error Management (TEM): threats are external events (weather, traffic, ATC), errors are crew actions; the aim is to anticipate, trap and recover.

Countermeasures: checklists, standard operating procedures, cross-monitoring, read-back, briefing, and sterile cockpit; they reduce error probability and increase detection.

Error rates: skilled performance is ~1 error in 1,000 actions; under high workload or fatigue error rates rise sharply; reliability is not constant.

Just culture: distinguishes human error (non-punitive) from reckless or intentional violation; reporting is encouraged to learn from errors.

Violation types: routine (accepted norm), situational (pressure), exceptional (rare); routine violations are the most dangerous because they become normalised.

Decision-making models: analytical (compare options), recognition-primed (pattern match), and naturalistic (time-pressured); pilots use all three.

DECIDE model: Detect, Estimate, Choose, Identify, Do, Evaluate; useful for structured in-flight decisions.

Risk assessment: probability × severity; use a risk matrix; accept only risk that is understood and mitigated; 'no-go' is a valid decision.

Judgement biases: confirmation bias, plan continuation bias (get-there-itis), anchoring, and availability heuristic; recognise and counter with a second opinion.

Plan continuation bias: the tendency to continue a plan despite changing cues; counter by setting explicit 'abort' criteria before flight.

Situational risk factors: fuel, weather, terrain, aircraft performance, crew experience, and time pressure; brief them before departure.

Crew decision-making: captain has final authority, but good crews use input from all; brief decision roles and 'stop' criteria.

Hazard vs risk: hazard is a potential source of harm; risk is the likelihood and severity of harm; manage risk, not just hazards.

CRM definition: effective use of all available resources - human, hardware, software, information - to achieve safe and efficient flight.

Leadership styles: autocratic (fast, low input), democratic (input, slower), laissez-faire (low control); the effective captain flexes style with the situation.

Assertiveness: first officer should state concern clearly with facts and a recommendation; use 'I am concerned because…' and escalate if not heard.

Communication: standard phraseology, read-back, and closed-loop communication; ambiguity is a major error source; confirm understanding.

Briefings: departure, approach, and threat briefings set shared mental models; include threats, roles, and 'what if' contingencies.

Barriers to communication: authority gradient, fear of criticism, fatigue, distraction, and noise; flatten the gradient with 'speak up' culture.

Teamwork: shared situational awareness, cross-monitoring, workload sharing, and mutual support; monitor each other's actions and call deviations.

Sterile cockpit: no non-essential activity below 10,000 ft (or per SOP); reduces distraction during critical phases.

Automation levels: from manual to fully automatic; higher automation reduces workload in some phases but can increase it in others (automation paradox).

Automation complacency: over-trust leads to reduced monitoring; counter with active monitoring and 'what is it doing, why, what next' checks.

Mode confusion: pilot misunderstands which automation mode is active; counter with mode awareness, FMA monitoring, and verbal callouts.

Automation bias: tendency to accept automated advice over own judgement; cross-check with raw data and independent sources.

Skill degradation: over-reliance on automation erodes manual flying and decision skills; practise manual flight regularly.

Automation surprises: unexpected mode changes or autopilot disconnects; brief expected modes and be ready to take over.

Human-centred automation: design should keep the pilot informed and in control; poor design increases error and workload.

Vigilance decrement: monitoring automated systems is fatiguing; use alerts, cross-checks, and periodic active scanning.

Workload: mental and physical demand relative to capacity; overload causes errors, underload causes boredom and complacency; aim for optimal load.

Yerkes-Dodson law: performance peaks at moderate arousal; too low (boredom) or too high (stress) degrades performance.

Workload measurement: subjective (NASA-TLX), physiological (heart rate), and performance-based; no single measure is complete.

Situational awareness (SA): perception of elements, comprehension of meaning, and projection of future status (Endsley's three levels).

SA loss: fixation, distraction, channelised attention, and 'out of the loop' during automation; counter with active scanning and verbal updates.

Threats to SA: fatigue, high workload, ambiguous information, and automation confusion; brief SA 'anchor points' and cross-check.

Crew SA: shared mental model of aircraft state, threats, and plan; verbalise and confirm to maintain shared SA.

Recovery from SA loss: re-orient with instruments, confirm position and mode, and reset priorities.

Circadian rhythm: internal ~24 h clock; body temperature lowest ~03:00-05:00 and ~14:00-16:00; alertness dips at these times.

Sleep: adults need ~7-9 h; sleep debt accumulates; recovery requires sleep, not just rest; naps of 20-30 min can restore alertness.

Fatigue types: acute (short-term, recover with sleep) and chronic (accumulated, requires extended rest); both degrade performance.

Fatigue effects: slowed reaction time, impaired vigilance, memory lapses, and poor decision-making; similar to alcohol effects at high levels.

Jet lag: crossing time zones desynchronises the circadian clock; eastward travel is usually harder; adaptation takes ~1 day per time zone.

Flight and duty time limitations (FTL): set by regulator (e.g., EASA, FAA); include maximum duty, minimum rest, and cumulative limits; they are a minimum, not a target.

Sleep hygiene: regular schedule, dark and quiet environment, avoid caffeine/alcohol before sleep; strategic napping on the ground and in flight where permitted.

Fatigue risk management: report fatigue, use FRMS where available, and plan duty with circadian awareness; do not rely on willpower.

Stress: response to demands exceeding resources; can be acute, chronic, or traumatic; some stress is necessary for performance.

Arousal: physiological activation; Yerkes-Dodson curve - moderate arousal optimises performance; high arousal narrows attention and increases errors.

Stress symptoms: increased heart rate, sweating, shallow breathing, muscle tension, and cognitive narrowing; recognise early and use breathing control.

Coping strategies: problem-focused (fix the issue) and emotion-focused (manage feelings); both are useful; avoid denial and 'press on' behaviour.

Pressure: time, social, and organisational pressure increase risk-taking and plan continuation; set explicit limits and use crew input.

Performance under pressure: overlearned skills and checklists hold up better than novel problem-solving; practise emergency procedures.

Fatigue and stress interaction: fatigue lowers stress tolerance and increases error; manage both together.

Post-incident stress: critical incident stress can affect performance; use peer support and professional help; do not self-medicate.