ATPL Human Performance key terms

A condition in which the tissues receive insufficient oxygen. In aviation it usually results from reduced oxygen partial pressure at altitude and impairs vision, judgement and consciousness before the person notices anything is wrong.

The period after loss of cabin pressure during which a crew member can still take effective, purposeful action before hypoxia makes them incapable. It shortens rapidly as altitude increases and is reduced by exertion.

A sudden loss of cabin pressure, typically from structural failure or a failed seal. It produces a loud bang, fog in the cabin and temperature drop, and gives the crew only seconds to don oxygen before hypoxia sets in.

Breathing faster or deeper than metabolic needs require, which washes out carbon dioxide and causes dizziness, tingling and cramps. In flight it is often triggered by stress and can be mistaken for hypoxia.

Pain or injury to gas-filled body cavities when ambient pressure changes faster than the gas can equalise. It most often affects the middle ear and sinuses during descent and the gut during climb.

Formation of nitrogen bubbles in tissues and blood when a person is exposed to a large, rapid pressure drop, for example after cabin decompression. Symptoms include joint pain, skin mottling and neurological signs.

A mismatch between the pilot's perceived attitude or motion and the true one, caused by misleading vestibular and visual cues without a reliable outside horizon. It is a major cause of fatal loss-of-control accidents.

A false sensation of pitch caused by linear acceleration or deceleration. Strong acceleration on take-off feels like a nose-up attitude and may provoke an unnecessary push, while deceleration feels like a dive.

The inner-ear organs that sense rotation and linear acceleration: the semicircular canals and the otoliths. They are reliable only for brief movements and give false signals during prolonged or coordinated flight.

The body's sense of pressure, touch and position from skin, muscles and joints. It tells a pilot which way gravity seems to pull, which helps orientation only when the aircraft is not accelerating.

Age-related hearing loss, typically starting with high frequencies and making speech in noise harder to understand. It adds to noise-induced loss and matters for radio communication and for detecting warning tones.

Permanent damage to hair cells in the inner ear from prolonged or intense sound exposure. It is cumulative and irreversible, so hearing protection and exposure limits are the only effective countermeasures.

Continuous broadband sound from engines, propellers and airflow, often above 80 dB. It masks speech and warning signals, causes fatigue, and over years damages hearing unless headsets or earplugs are used.

The internal roughly 24-hour cycle that governs alertness, body temperature and hormone release. It is set mainly by light and resists rapid change, so it desynchronises after crossing time zones or flying at night.

A temporary disturbance of sleep, mood and performance after rapid travel across time zones, caused by the body clock lagging behind local time. Eastward travel is generally harder to adapt to than westward.

Reduced alertness and slower thinking immediately after waking, especially from deep sleep or after a short nap. It can last many minutes and is dangerous if the person must act at once, such as after a cockpit rest.

A physiological state of reduced mental or physical performance caused by sleep loss, long duty or high workload. It impairs reaction time and vigilance and cannot be overcome reliably by willpower or motivation.

The progressive decline in attention and detection of rare signals during a long, monotonous task such as monitoring instruments on cruise. It occurs even in motivated people and is a reason for structured task sharing.

A self-satisfied state of low vigilance that arises when everything has gone well for a long time. It leads crews to skip checks or accept non-standard situations without challenge, and is a common precursor of error.

An accurate, up-to-date picture of what is happening around the aircraft and what it means for the flight ahead. It is built from perception, understanding and projection, and is lost gradually rather than instantly.

The mental and physical effort needed to meet task demands. Both very high and very low workload degrade performance: overload causes tunnelling and omissions, while underload invites boredom and inattention.

A actions or decisions by a person that fail to achieve the intended outcome within the rules of the system. Errors are normal consequences of human limitations and are better managed by changing conditions than by blaming individuals.

A sequence of linked failures, latent conditions and unsafe acts that together lead to an accident. Breaking any single link, for example by a challenge or a cross-check, can prevent the outcome.

A safety approach in which honest mistakes are reported and learned from without punishment, while reckless or deliberate violations are still sanctioned. It encourages open reporting, which is essential for managing human error.

A framework describing human factors as the fit between Software, Hardware, Environment and the Liveware at the centre, plus the Liveware-Liveware interface between people. Mismatches at any interface create error potential.

Training and practice in using all available resources, including other crew, equipment and information, to achieve safe flight. It emphasises communication, leadership, briefings and challenge in the cockpit.

The skill of stating a concern clearly and persistently, with evidence, until it is acknowledged. It balances deference to authority against the duty to speak up when something appears unsafe.

The perceived difference in power between a leader and team members. Too steep a gradient silences junior crew, while too flat a one blurs command, so a moderate gradient supports safe challenge.

The process of choosing between options under uncertainty and time pressure. In aviation it combines situation assessment, option generation, risk evaluation and commitment, and is improved by structured models and shared input.

The tendency to seek and interpret information in ways that support a belief already held, while ignoring contrary evidence. It can make a crew persist with a wrong diagnosis or a deteriorating plan.

The tendency to keep following an original plan, such as a destination or approach, despite new evidence that it is no longer safe. It explains many weather-related and fuel-related accidents.

The body's response to demands that exceed or threaten the person's ability to cope. Short-term stress can sharpen performance, but prolonged stress impairs memory, judgement and sleep and harms health.

The general level of physiological and mental activation. Performance is best at moderate arousal and falls when arousal is too low, as in boredom, or too high, as in fear or panic.

The active interpretation of sensory information into a meaningful picture. It depends on expectation and experience, so it can be wrong even when the senses themselves are working correctly.

A systematic misinterpretation of real sensory input, such as a black-hole approach making a runway seem closer than it is. Illusions are predictable and can be countered by training and instrument cross-checks.

Pain in the face or forehead during pressure change when a blocked sinus cannot equalise. It is worse on descent, can be severe enough to impair a pilot, and should be treated as a reason not to fly.

Rapid or deep breathing that lowers blood carbon dioxide, producing dizziness, tingling and muscle tightness. In flight it is often triggered by stress and can be mistaken for hypoxia.

The state in which the internal body clock is out of step with local time or the duty schedule, causing poor sleep and reduced alertness. It is the underlying mechanism of jet lag and shift-work problems.