EASA PPL Human Performance & Limitations (P20) — Study Guide

Human Performance & Limitations surprises students who expect only charts and regulations. It is fundamentally about why pilots fail: physiology, psychology, fatigue, stress, and communication under load. The P20 paper is 20 questions in 30 minutes; at 75% you need 15 correct.

Treat it as operational knowledge — hypoxia symptoms, illusions, fatigue traps — and it sticks. Treat it as trivia, and subtle distinction questions (hypoxia vs hyperventilation) cost marks.

Syllabus shape

EASA splits the subject into physiology (body at altitude, vision, cardio-respiratory basics, hypoxia, hyperventilation, spatial disorientation, G-load) and psychology (attention, memory, situational awareness, decisions, stress, fatigue, CRM-style communication).

Altitude, hypoxia, and hyperventilation

Atmospheric pressure falls with altitude; oxygen fraction stays ~21%, but partial pressure drops — so less oxygen reaches tissues. That is the mechanism behind hypoxia. In unpressurised PPL flying severe hypoxia is uncommon but not impossible, especially combined with illness, alcohol, exertion, or anxiety.

Hypoxia impairs judgement early; victims may feel oddly well. Symptoms include faster breathing, cyanosis, headache, dizziness, confusion, and eventual LOC. Response: descend and use supplemental oxygen if fitted and appropriate.

Hyperventilation (stress/anxiety-driven over-breathing) blows off CO₂, alkalises blood, and can mimic hypoxia: tingling, dizziness, visual disturbance, muscle spasms, syncope. Treatment is slower controlled breathing — not oxygen alone (oxygen does not fix CO₂ washout and may distract from the real fix). Examiners love vignettes that mention anxiety + tingling to steer you toward hyperventilation even when altitude is nonzero.

Spatial disorientation

The vestibular system senses acceleration, not sustained motion. In a prolonged bank without horizon cues, your inner ear "forgets" the turn; correcting by feel can tighten a spiral. Trust instruments when visual attitude references are absent — sensations will lie. The syllabus covers somatogravic illusions, leans, coriolis effects at a conceptual level: know why bodily feelings are unreliable in IMC or dark night with no horizon.

Vision and night flying

Central vision is sharp and colour-rich; peripheral vision detects motion better and works at lower light via rods. Rods are scarce in the fovea — so off-centre viewing helps spot weak lights at night.

Full dark adaptation takes on the order of 30 minutes; bright light resets it. Night pilots minimise unnecessary glare before and during flight.

Fitness to fly

• Alcohol: impairment begins below legal driving limits; 8 hours bottle-to-throttle is a minimum regulatory reference — residual effects can last longer.
• Medication: antihistamines, sedatives, many cold remedies — assume no-go unless an AME clears you.
• Illness: even "mild" colds disturb sleep and cognition and can trap pressure in sinuses/ears during climb/descent.

Stress, arousal, and fatigue

The Yerkes–Dodson curve is an inverted U: too little arousal hurts performance (boredom/inattention); moderate arousal helps; excessive stress degrades judgement (tunnel vision, fixation). Questions often add a stressor to a pilot already highly aroused — expect performance to fall, not rise.

Fatigue dulls reaction time, memory, multi-tasking, and self-awareness — tired crews underestimate impairment. The only remedy is sleep. Circadian lows (very early morning, post-lunch dip) compound fatigue even after "enough" sleep on paper.

Attention, workload, situational awareness

Humans do not truly multitask; they task-switch with attentional penalties. Under load, selective attention drops apparently irrelevant cues — sometimes the cue that mattered.

Situational awareness is often framed as three levels: perceive → comprehend → project ahead. Accidents frequently show loss starting at projection, then comprehension, then raw perception — by then you are purely reactive.

Error models distinguish slips/lapses (skill), rule/knowledge mistakes, and deliberate violations. Biases such as confirmation bias, plan continuation, and get-home-itis push pilots to continue into deteriorating conditions — experience does not immunise you; explicit decision points do.

CRM and communication (PPL scope)

CRM ideas apply even solo: brief clearly, verbalise decisions, admit uncertainty to ATC, avoid ambiguous phraseology. Communication breaks down via noise, workload, expectation bias ("hearing" what you predicted), and ambiguous language — awareness beats memorising academic models.

Where marks disappear

• Hypoxia vs hyperventilation — read triggers and treatments, not just symptom lists.
• Yerkes–Dodson direction — too much stress always hurts once past the peak.
• Dark adaptation duration (~30 minutes) and off-centre night scanning — factual recall.

How to prepare

Understand mechanisms first, then drill questions that force scenario discrimination. Most candidates stabilise scores within a handful of focused sessions because the subject rewards conceptual clarity once you stop treating it as rote memorisation.