CAAS PPL Human Performance Study Guide

Aviation accident statistics consistently attribute roughly three quarters of accidents to human-factor causes rather than mechanical failure. The Human Performance (HP) syllabus exists to introduce pilots to the physiological and psychological limits within which they must operate, and to teach the decision-making frameworks that prevent small errors from compounding into accidents. The CAAS PPL exam tests definitions, recognises symptoms, and asks you to choose the correct response — so you must learn both the science and the procedural response.

A useful framing is the SHELL model (Software, Hardware, Environment, Liveware, and the central Liveware — the pilot). Most human-factor accidents are mismatches between the pilot (central liveware) and one of the other elements: misreading a checklist (software), fumbling a knob (hardware), being startled by turbulence (environment), or miscommunicating with ATC (liveware). The model is useful because it reminds you that the human is not a fixed component but a variable one whose capacity changes hour to hour with fatigue, stress, oxygen and workload — and that the surrounding elements should be designed and managed to suit that variability rather than the other way round.

In broad terms the exam concentrates on five recurring themes, and it pays to keep them in mind as you read: how the body is supplied with oxygen and what goes wrong when the supply falls (hypoxia, hyperventilation, the effects of reduced pressure on the ears and sinuses); how the senses can be fooled (vision, the vestibular balance organs and spatial disorientation); what degrades the pilot (alcohol, medication, fatigue, dehydration, carbon monoxide and minor illness); how the mind processes information (attention, memory, workload, arousal and situational awareness); and how errors are managed(hazardous attitudes, decision-making models and threat-and-error management). Almost every question maps onto one of those themes, so if you can place a question in its theme you are usually halfway to the answer. The recurring exam pattern is recognition: you are shown a set of symptoms, an altitude, or a scenario and asked to name the condition, identify the receptor or illusion, or choose the correct corrective action.

Before every flight a pilot should run the IMSAFE self-check. It is short enough to do while walking to the aircraft and specific enough to catch most common impairments:

• Illness — even a mild cold can block sinuses and Eustachian tubes, causing painful pressure imbalance during descent.
• Medication — many over-the-counter drugs (antihistamines, motion-sickness pills, decongestants) impair judgement. Consult an aviation medical examiner if in doubt.
• Stress — financial, relational or work stress narrows attention and increases error rates.
• Alcohol — see the discussion below.
• Fatigue — the single most under-recognised hazard. Cumulative fatigue across a busy week is as dangerous as a sleepless night.
• Emotion — recent argument, bereavement, or significant anger should ground the flight.

IMSAFE is a screening tool, not a diagnosis. If any item triggers concern, the safe decision is to delay or cancel. A useful question to ask yourself: would I take a paying passenger today? If the answer is no, fly with an instructor or not at all.

Hypoxia is insufficient oxygen reaching the body's tissues. It is silent, progressive, and is the single greatest physiological hazard at altitude. There are four classical categories:

• Hypoxic (hypobaric) hypoxia — caused by reduced partial pressure of oxygen, i.e., altitude. This is the type that matters for unpressurised PPL flight.
• Hypaemic (anaemic) hypoxia — the blood's ability to carry oxygen is reduced. Causes include anaemia, blood loss and, importantly, carbon monoxide poisoning (CO binds to haemoglobin 200+ times more strongly than oxygen).
• Stagnant (ischaemic) hypoxia — circulation is impaired even though blood is normal. Causes include G-forces, cold extremities, or shock.
• Histotoxic hypoxia — the tissues themselves cannot use the oxygen delivered. Alcohol and cyanide are the classic causes.

Symptoms include euphoria, impaired judgement, blurred vision, tingling, cyanosis (blue lips and nail beds), and eventually unconsciousness. The order of onset varies between individuals, which is why regulators do not permit pilots to "feel their way" — they require supplemental oxygen above specific altitudes regardless of subjective symptoms.

The Time of Useful Consciousness (TUC) is the interval between exposure to low oxygen and the point at which the pilot can no longer take corrective action. Typical figures for an unacclimatised person at rest are:

Rapid decompression roughly halves the TUC. The exam will expect you to know that TUC decreases dramatically above about 25,000 ft and that immediate descent is the correct response to suspected hypoxia.

Hyperventilation is over-breathing — typically a stress response — which washes carbon dioxide out of the blood. The resulting alkalosis produces dizziness, tingling in the extremities and around the mouth, muscle spasm, and eventually unconsciousness. Critically, many symptoms overlap with hypoxia: dizziness, visual disturbance, impaired judgement.

The diagnostic difficulty is real, and the safe procedure is to treat for hypoxia first if there is any doubt: select 100% oxygen if available, descend below 10,000 ft, and slow the breathing rate. Breathing into a paper bag or talking aloud (which forces slower breathing) helps restore the CO₂ balance once hypoxia has been excluded. The exam may ask you to identify the cause from symptoms in a scenario — pay attention to altitude (low altitude favours hyperventilation; high altitude favours hypoxia) and to whether oxygen has been administered without effect.

Hypoxia makes more sense once you understand normal respiration. Air is roughly 21% oxygen at every altitude — that proportion does not change. What changes with height is the total air pressure, and therefore the partial pressure of oxygen, which is the part of the pressure contributed by oxygen alone. It is the partial pressure of oxygen in the lungs, not the percentage in the air, that drives oxygen across the thin walls of the alveoli and into the blood. At about 18,000 ft the atmospheric pressure has fallen to roughly half its sea-level value, so the partial pressure of oxygen is roughly halved as well — and the oxygen gradient into the blood is too weak to keep the tissues fully supplied. This is the physical reason that supplemental oxygen becomes necessary with height even though the air is still one-fifth oxygen.

Two gas laws underpin the rest of aviation physiology. Boyle's law states that, at constant temperature, the volume of a fixed mass of gas is inversely proportional to its pressure — so as you climb and pressure falls, trapped gas expands; as you descend and pressure rises, it contracts. Henry's law states that the amount of a gas dissolved in a liquid is proportional to the pressure of that gas above the liquid — which is why dissolved nitrogen can come out of solution as bubbles if pressure drops too far or too fast (decompression sickness, mainly a concern after diving or at very high altitude rather than in normal PPL flight).

Boyle's law explains the most common minor injuries of flight, all caused by trapped expanding or contracting gas:

The ear is the one to understand properly because it is the most common and the most painful. The middle ear is an air pocket connected to the back of the throat by the Eustachian tube. On the climb the expanding middle-ear air vents out easily, so the climb is rarely uncomfortable. On the descent the outside pressure rises and the tube must open inward to let air back in — but the tube is a one-way-biased flap that resists inward flow, so it can fail to equalise. The result is a painful, inward-bulging eardrum, muffled hearing, and occasionally vertigo. The cure is to actively open the tube by swallowing, yawning, or the Valsalva manoeuvre (pinch the nose and gently blow against it). A head cold or hay fever swells the lining and can make equalisation impossible — which is exactly why the I in IMSAFE matters and why flying with a cold is a poor idea, especially as a passenger who cannot control the rate of descent.

A short worked example pulls the gas laws together. Suppose you fly a balloon-like sealed bag from sea level (about 1,013 hPa) up to roughly 18,000 ft (about 500 hPa). By Boyle's law the volume roughly doubles, because the pressure has roughly halved. The same physics inflates trapped gut gas on a fast climb and is why the eardrum bulges outward on the way up and inward on the way down.

Spatial disorientation is the mismatch between the body's sensed orientation and reality. The three balance senses (vision, vestibular system in the inner ear, and proprioception from muscles and joints) are well-calibrated for walking on the Earth's surface but can be tricked in flight, especially in cloud or at night. Of the three, vision normally dominates and keeps the other two honest; remove the outside horizon, as cloud or a dark night does, and the unreliable inner-ear and seat-of-the-pants senses take over with no reference to correct them.

The vestibular system sits in the inner ear and has two parts. The three semicircular canals, set at right angles to one another, are fluid-filled loops that detect angular acceleration — the start and stop of a turn, pitch or roll. The otolith organs detect linear acceleration and the pull of gravity. The fatal weakness of both is that they sense change, not steady state. In a turn held at a constant rate for more than about twenty seconds, the fluid in the canals catches up with the canal wall and the sensation of turning fades away, so a sustained turn comes to feel like straight flight. The otoliths, meanwhile, cannot tell the forward push of acceleration apart from the backward tilt of gravity. These two limitations generate every classic illusion below. Three named ones are likely to appear in the exam:

• Somatogravic illusion — caused by linear acceleration. A take-off acceleration with no outside reference creates the false sensation of nose-up pitch, leading the pilot to push the nose down toward the ground. A common night and IMC accident.
• Somatogyral illusion — caused by angular acceleration. After a prolonged turn, the fluid in the semicircular canals stops moving relative to the canal, so the pilot feels "wings level" even while still turning. Rolling out then produces a false sensation of turning in the opposite direction (the "graveyard spiral").
• The Leans — a subtle, false sensation of bank caused by a slow roll the pilot did not notice. Correcting by feel rolls the aircraft into a bank while the pilot believes it is level.

The single most-tested learning point is the same in all cases: trust the instruments. Vestibular illusions cannot be reasoned away by feel. If you find yourself in IMC by accident as a VFR-only pilot, an immediate 180° turn back into VMC, controlled by reference to the attitude indicator, is the standard response.

The retina contains two kinds of photoreceptor. Cones are concentrated in the centre of the retina (the fovea) and are responsible for colour vision and fine detail; they perform well in good light but poorly in dim conditions. Rods are concentrated outside the fovea (peripheral retina), are far more sensitive in low light, but do not perceive colour or fine detail.

Two practical exam points follow from this anatomy. First, night vision adaptation(when rods reach maximum sensitivity) takes approximately 30 minutes in darkness — bright white light immediately resets the process. Red cockpit lighting is therefore preferred at night because red light has less effect on rod sensitivity. Second, at night you should look slightly to the side of an object rather than directly at it, because the rod-rich peripheral retina sees more in the dark than the cone-rich fovea — this is called off-centre scanning.

Other visual issues to know:

• Empty-field myopia — in a featureless sky the eye relaxes to a focus of about 1-2 m, missing distant traffic. Scan systematically using fixation points (cloud edges, the horizon).
• Blossom effect — an approaching aircraft is invisible until very close, then appears to suddenly grow. Effective lookout requires sectoring the sky and pausing on each sector.
• Glare — bright sun or a wet runway reduces contrast; sunglasses (preferably non-polarising for aircraft with composite or laminated windscreens) are useful.

PPL flying does not normally produce sustained high-g loads, but you should know the basics. Positive g pushes blood away from the head, producing greyout, blackout and finally g-induced loss of consciousness (G-LOC) typically between +4 g and +6 g for an untrained person. Negative g pushes blood toward the head, producing redout and is far less tolerated. Hydration, muscle tension, and the anti-g straining manoeuvre raise tolerance, but the simplest mitigation is to keep manoeuvres gentle.

Alcohol is a histotoxic poison at the cellular level and a CNS depressant. The ICAO-recommended rule is "8 hours from bottle to throttle", and many jurisdictions, Singapore included, impose stricter limits and may set a blood-alcohol limit (commonly 0.02% or lower for flight-crew duty). Even small amounts of alcohol degrade decision-making and inner-ear function for many hours after the legal time limit has passed. The combination of alcohol and altitude is more debilitating than either alone.

Fatigue is divided into acute fatigue (from a single bad night or long duty) and chronic fatigue (accumulated over weeks). Chronic fatigue cannot be fixed by one good night's sleep. Circadian factors matter: the early-morning hours and early afternoon (post-lunch dip) are physiological low points where errors increase. Sleep hygiene, regular schedule, and the discipline to cancel a flight when fatigued are the only real defences.

A light-aircraft cockpit is a genuinely hostile noise environment: engine, propeller, slipstream and radio combine to produce sustained levels that, over a career, will damage hearing if left unprotected. Sound is collected by the outer ear, turned into mechanical vibration by the eardrum and the chain of three small bones in the middle ear, and converted into nerve signals by the hair cells of the fluid-filled cochlea in the inner ear. Those hair cells do not regenerate, so the damage is permanent.

The single most-tested fact is that noise-induced hearing loss attacks the high frequencies first. A pilot losing high-frequency hearing may not notice for years, because speech and everyday sound sit lower down the range, yet consonants and warning tones live in the high band that is quietly being lost. Sustained exposure above roughly 85–90 dB is generally taken as the threshold for cumulative damage, with risk rising steeply as level and exposure time increase; an unsilenced light-aircraft cabin can comfortably exceed that. The defences are simple and not optional — a well-fitted headset (ideally with active noise reduction) or, at minimum, ear plugs. Beyond preserving hearing, good ear protection lowers fatigue and improves radio intelligibility, both of which feed straight back into safety.

Two slow, silent hazards deserve their own section because both creep up unnoticed and both are easy to prevent. Carbon monoxide (CO) is a colourless, odourless, tasteless gas produced by incomplete combustion. In light aircraft it most often reaches the cabin through a cracked exhaust muffler feeding the cabin-heat system, so the classic warning sign is symptoms that appear or worsen after the heater is selected on. CO binds to haemoglobin more than 200 times more strongly than oxygen does, so even a trace concentration progressively locks up the blood's oxygen-carrying capacity — producing hypaemic (anaemic) hypoxia with the same insidious symptoms as altitude hypoxia: headache, drowsiness, dizziness, impaired judgement and, eventually, unconsciousness. Because CO cannot be smelled or seen, the only reliable detection is a dedicated CO detector (the cheap spot-type card that darkens, or an electronic alarm). If CO is suspected the actions are immediate: turn the cabin heat off, open fresh-air vents and windows, select 100% oxygen if fitted, and land as soon as practicable.

Dehydration is under-rated. Cabin air is dry, an open canopy or warm climate drives fluid loss, and pilots routinely under-drink because they wish to avoid the inconvenience of needing the toilet in flight. The result is reduced blood volume, headache, tiredness, slower reaction time and impaired concentration — symptoms that overlap with fatigue and mild hypoxia and so are easily mis-attributed. Heat stress compounds it. The fix is unglamorous: drink water steadily before and during flight, recognise that thirst lags behind actual need, and treat the urge to ration fluid as a hazard in its own right.

Flying is fundamentally an information-processing task, and the syllabus expects a working model of how the mind handles information. Sensory input is filtered by attention, briefly held and manipulated in short-term (working) memory, and either acted on or transferred into long-term memory. Working memory is the bottleneck: it holds only a handful of items for a few seconds, which is precisely why a long ATC clearance must be written down rather than trusted to memory, and why checklists exist at all. Skills practised to the point of automaticity bypass this bottleneck — an experienced pilot flies the aircraft without conscious thought, freeing working memory for navigation, weather and decisions.

Performance depends on arousal, and the relationship is an inverted U described by the Yerkes–Dodson law: too little arousal (boredom, the long stable cruise) and vigilance lapses into hypovigilance; too much (an emergency, an overload of simultaneous demands) and attention narrows, tasks get shed, and errors multiply. Peak performance sits in the middle. Two failure modes flow from this. Under high load a pilot may suffer attentional tunnelling— fixating on one problem (a warning light, a stuck gear indicator) while flying a perfectly good aircraft into the ground, the textbook example being the crew so absorbed in a bulb that no one flew the aeroplane. Under low load, monotony erodes the scan and the pilot stops actually looking at the instruments they are staring at.

Situational awareness (SA) ties these ideas together. It is usually described in three levels: perceiving what is happening (traffic, fuel, weather, position), comprehending what it means, and projecting what will happen next. Good decisions depend on accurate SA, and the danger signs of losing it are worth memorising because the exam likes them: ambiguity, fixation, confusion, failing to meet expected checkpoints (being late or off-track), nobody flying the aircraft, and an undershoot or overshoot of targets. The cure is to manage workload before it manages you — stay ahead of the aircraft by planning, briefing and prioritising, and apply the timeless rule aviate, navigate, communicate: fly the aircraft first, work out where you are going second, and talk on the radio last.

Errors are not random moral failings; they fall into recognisable types, and naming the type points to the defence. A standard breakdown distinguishes slips and lapses(you intended the right action but executed it wrongly, or forgot a step — flipping the wrong switch, omitting an item) from mistakes (you did exactly what you intended, but the plan itself was wrong — a navigation error or a bad weather decision). Slips and lapses are skill-based breakdowns best defended by checklists, standard flows and unhurried habit; mistakes are knowledge-based and are defended by training, planning and seeking a second opinion. A third category, violations, is the deliberate decision to break a rule, and it sits closer to the hazardous attitudes than to honest error.

Threat-and-Error Management (TEM) is the modern framework that brings this together. It treats the operating world as full of threats — anything outside the pilot's influence that increases complexity, such as weather, terrain, busy airspace, an unfamiliar aerodrome or a technical snag. Threats lead to errors if not managed, and unmanaged errors lead to undesired aircraft states (low and slow on approach, off altitude, lost). The aim is to break the chain as early as possible: anticipate and avoid threats where you can, trap errors before they bite, and recover promptly from any undesired state. The practical value of TEM is the mindset it builds — you brief the threats before they arrive (a crosswind, a high-density-altitude departure, a radio-busy circuit), so that when one materialises you are managing a known threat rather than reacting to a surprise.

One last idea connects TEM back to attitudes and decision-making: the error chain. Accidents almost never have a single cause; they are the last link in a chain of small, individually survivable events — a late start, a rushed brief, a missed fuel check, deteriorating weather, a tired pilot pressing on. Any one link broken stops the accident. That is the whole point of the discipline in this syllabus: each tool — IMSAFE, personal minima, the checklist, the 180° turn out of cloud, trusting the instruments — exists to break a link before the chain completes.

Modern PPL training teaches decision-making as a discipline. Two frameworks dominate the syllabus.

The DECIDE model is a six-step loop applied throughout a flight:

1. Detect the change.
2. Estimate its significance.
3. Choose a desirable outcome.
4. Identify actions to control the change.
5. Do — take action.
6. Evaluate the effect.

The 3P model is shorter and easier to apply under pressure: Perceive the hazard, Process its implications (using a structure such as PAVE — Pilot, Aircraft, enVironment, External pressures), and Perform the best response.

Both are antidotes to the five hazardous attitudes the syllabus expects you to recognise in yourself: anti-authority, impulsivity, invulnerability, macho, and resignation. Each has a textbook antidote ("follow the rules — they are usually right", "not so fast, think first", "it could happen to me", "taking chances is foolish", "I am not helpless"). The exam often asks you to match an attitude to an antidote or to a scenario.

Two final ideas worth your attention. Get-there-itis is the well-named pressure to complete a flight despite deteriorating conditions; the cure is to set personal minima before launching and to write them on the flight plan. Crew Resource Management (CRM) — although developed for multi-crew operations — applies in single-pilot flying as well: use checklists, brief passengers, and treat ATC, ground crew and even an aviation-savvy passenger as additional resources rather than as audience.

A handful of errors recur in Human Performance exams every year. Learn to avoid them and you will pick up easy marks that better-prepared candidates routinely drop.

• Confusing the percentage of oxygen with its partial pressure. Air stays 21% oxygen at altitude; it is the falling partial pressure that causes hypoxia. Answers that say the percentage of oxygen decreases with height are wrong.
• Treating hypoxia and hyperventilation as opposites in altitude. Their symptoms overlap heavily. The discriminators are altitude (high favours hypoxia, low favours hyperventilation) and response to oxygen. When in doubt, treat for hypoxia first because it is the more immediately lethal.
• Believing you can "feel" your orientation in cloud. The vestibular senses detect change, not steady state, so they cannot be trusted without a visual horizon. The exam answer is always to trust the instruments, not the seat of your pants.
• Mixing up rods and cones. Rods are peripheral, low-light, no colour, and give night vision; cones are central (foveal), need good light, and give colour and detail. Off-centre scanning works because the rods sit off-centre.
• Forgetting that ear and sinus trouble bite hardest on descent. The climb usually vents freely; the descent requires air back in through a reluctant Eustachian tube, which is why a head cold is so dangerous on the way down.
• Assuming you can smell carbon monoxide. CO is odourless, colourless and tasteless. The only reliable detection is a CO detector, and the classic trigger is selecting cabin heat.
• Thinking one good night's sleep cures chronic fatigue. It cures acute fatigue. Chronic fatigue accumulates over weeks and needs sustained rest and schedule recovery.
• Reading "8 hours bottle to throttle" as fully recovered. Eight hours is a legal minimum, not a return to full function; inner-ear and judgement effects linger far longer, and alcohol's impairment is amplified by altitude.
• Matching a hazardous attitude to the wrong antidote. Drill the five attitude–antidote pairs as a set, because the exam loves to scramble them.

Human Performance rewards a different study method from the more calculation-heavy subjects. It is overwhelmingly a recognition and definition paper, so the most efficient preparation is spaced flashcard revision rather than long worked problems. Split your cards into two decks that mirror the structure of this guide:

1. Physiology deck — respiration and the oxygen partial-pressure idea, the four types of hypoxia, hyperventilation, the gas laws and ear/sinus block, rods versus cones and night vision, hearing and the high-frequency point, carbon monoxide, alcohol, fatigue and dehydration.
2. Psychology deck — the named spatial-disorientation illusions, situational awareness and its loss, information processing and arousal, human-error types, threat-and-error management, the hazardous attitudes and their antidotes, and the IMSAFE / DECIDE / 3P / PAVE frameworks.

A few tactics raise scores reliably. First, learn the short list of numbers that students consistently misremember — the rough 10,000 ft threshold where unsupplemented hypoxia begins to matter, the halving of oxygen partial pressure by about 18,000 ft, the 30-minute dark-adaptation time, and the 85–90 dB noise threshold — and treat any verifiable regulatory figure (exact alcohol limits, medication and post-anaesthetic waiting periods) by checking the current CAAS examination requirements and medical guidance rather than relying on a half-remembered number, since these can differ between jurisdictions.

Second, build the habit of placing each question in its theme before answering: is this about oxygen supply, a fooled sense, a degrading agent, information processing, or error management? Naming the theme usually narrows four options to two. Third, watch for scenario questions(night approach, motion sickness, a heater-on headache, a VFR pilot in cloud) and recall that they almost always have a single procedural answer — descend and use oxygen for hypoxia, trust the instruments and turn 180° out of cloud, minimise head movement for motion sickness, cabin-heat off for suspected CO. Finally, do not over-think: Human Performance is built to test whether you know the concept, not whether you can out-argue the examiner, so the textbook conservative answer is almost always the intended one.

Across the 41 Human Performance questions in this bank, the emphasis is on definitions, threshold numbers and the recognition of named illusions and conditions rather than on the deeper science. Many of the items can be answered with one or two pieces of factual knowledge — the altitude at which unsupplemented hypoxia begins, what "the leans" means, which receptors give peripheral vision — and the bank rewards rote memorisation. Where scenarios appear, they are short and tend to be about night approach, motion sickness or risk assessment, so the clusters below capture nearly the full surface area of the quiz.

• Hypoxia thresholds and partial pressure: know that unsupplemented hypoxia becomes a problem above roughly 10,000 ft, and that the partial pressure of oxygen at 18,000 ft is about half its sea-level value. The TUC table from the guide above is the next layer; the quiz, though, tests the threshold rather than precise TUC figures.
• Carbon monoxide: a small recurring cluster. CO is odourless and colourless, binds to haemoglobin far more strongly than oxygen (anaemic / hypaemic hypoxia), and the only reliable detection method is a dedicated CO detector — not smell, not visual cues.
• Vision — rods, cones and night flying: rods give peripheral and low-light vision, cones give central and colour vision; an image you focus on lands on the retina; rods are degraded by age, alcohol, CO and hypoxia; off-centre scanning is the night-vision technique that follows from this anatomy.
• Spatial disorientation and named illusions: "the leans" (false bank after a slow undetected roll), the runway-slope and terrain illusion on approach, the black-hole effect over featureless terrain at night (which biases the pilot to fly low). The universal answer when visual references are lost is to disregard the vestibular sense and trust the instruments.
• Hearing loss and noise: the first symptom of noise-induced hearing loss is loss of high-frequency hearing; sustained exposure above about 90 dB causes damage (some sources cite a lower onset threshold). Ear protection in a noisy cabin is not optional.
• Alcohol limits and medication: the recommended blood-alcohol limit for flight crew (often expressed as 20 mg per 100 ml), the residual inner-ear effects that last about 24 hours after the legal limit has lapsed, the eight-hours-from-bottle-to-throttle rule, and the 48-hour wait after a general anaesthetic. Medication during a flight is only acceptable on the direction of a certified aviation medical examiner.
• Decision-making, risk assessment and IMSAFE: the three-phase decision model (gather information, identify the problem, execute), the two components of risk balancing (the individual's knowledge and attitude toward the risk), and that IMSAFE is the standard pre-flight fitness self-check.
• Personality, arousal and stress: a pilot's personality is changeable (it is shaped by external factors), social environment is an external factor in decision-making, and long stable cruise is the classic low-arousal phase where vigilance lapses. Hypovigilance means diminished alertness.
• Motion sickness, gastroenteritis and minor illness: the practical cure for motion sickness is to minimise head movement; gastroenteritis comes from contaminated or reheated food and water; a head cold is an under-recognised barrier to safe descent.
• G-tolerance and physiological vocabulary: pulling out of a dive imposes positive g and the associated greyout/blackout sequence; hypertension is high blood pressure (not to be confused with hyperthermia or hypotension); short-term memory is also called working memory.

Because Human Performance is concentrated on definitions, the most effective preparation is two short revision sessions of flashcards — one on physiology (hypoxia, vision, hearing, CO, alcohol) and one on psychology and decision-making (illusions, risk, IMSAFE, arousal). After those, the practice quiz will mostly reinforce the few numbers (the 10,000 ft hypoxia threshold, the 24-hour alcohol residue, the 48-hour anaesthetic wait, the 20 mg blood-alcohol level) that students consistently misremember.