CPL Human Performance key terms

A state in which the tissues receive insufficient oxygen. In flight it may result from high altitude, faulty oxygen equipment, or reduced oxygen-carrying capacity of the blood, and impairs judgement before the pilot notices.

The period between loss of adequate oxygen supply and the point at which a person can no longer take effective protective action. It shortens rapidly as altitude increases and is reduced by cold, exertion, and fatigue.

Breathing faster or deeper than metabolic needs require, lowering blood carbon dioxide. Symptoms such as dizziness, tingling, and chest tightness resemble hypoxia, so the pilot should treat the symptoms as hypoxia first.

Formation of nitrogen bubbles in body tissues when ambient pressure falls too quickly, as in a rapid cabin decompression or after diving before flight. Joint pain, skin mottling, and neurological symptoms require descent and medical care.

Uptake of odourless carbon monoxide from exhaust or heater leaks, which displaces oxygen on haemoglobin. Headache, confusion, and a feeling of warmth progress to unconsciousness without warning, so suspicion alone warrants oxygen and descent.

A false sensation of pitch caused by linear acceleration or deceleration. Strong acceleration feels like a nose-up attitude, prompting a pilot to push forward, while deceleration feels like a nose-down attitude.

A false sensation of rotation after a sustained turn, caused by fluid continuing to move in the semicircular canals when the aircraft stops turning. The pilot may feel a turn in the opposite direction and correct incorrectly.

A false sensation of banking during a coordinated turn or after rolling out, caused by the semicircular canals responding to angular acceleration rather than sustained rotation. Relying on it leads to unintended control inputs.

The inner-ear organs that sense rotation through the semicircular canals and gravity and acceleration through the otoliths. It cannot distinguish sustained turns from straight flight, making it unreliable without visual reference.

The body's pressure, touch, and position sensors in skin, muscles, and joints. In flight these sensors can create false impressions of attitude, particularly during acceleration or in turbulence, when seat-of-the-pants feel is misleading.

Failure to correctly perceive the aircraft's position or motion relative to the ground. It arises when visual, vestibular, and somatosensory information conflict, and is most dangerous without a visible horizon or outside reference.

A misleading perception of the outside world, such as a runway that appears closer, higher, or narrower than it is. Examples include black-hole approaches, sloping terrain, and runway width effects, all of which distort the approach path.

An approach at night over featureless terrain with few ground lights, which removes visual cues and makes the pilot fly too low and too steep. An instrument or glidepath reference is needed to counter it.

Three fluid-filled loops in the inner ear, one for each plane of rotation, that detect angular acceleration. They adapt to sustained rotation and can signal a false turn after the aircraft has stopped turning.

Inner-ear structures that sense gravity and linear acceleration. Because they cannot separate the two, acceleration can be interpreted as a change in pitch, producing the somatogravic illusion.

Disorientation or nausea caused by a light flickering at a frequency near that of brain rhythms, for example sunlight through a turning rotor or propeller. Removing or blocking the flickering source resolves it.

Nearsightedness that develops when looking into a featureless field such as cloud, fog, or a dark night sky. The eye relaxes to a resting focus of about one metre, so distant objects appear blurred and may be missed.

Vision in dim light, mediated by rod cells that are sensitive to low illumination but poor at detail and colour. Rods are concentrated away from the centre of the retina, so off-centre viewing improves detection of dim objects.

The gradual increase in visual sensitivity after moving from bright to dim light, taking roughly 20 to 30 minutes for full effect. Bright light, smoking, and low oxygen slow or reverse the process.

Age-related hearing loss, typically affecting high frequencies first. It reduces the ability to hear speech in noise and warning tones, and is accelerated by repeated exposure to loud noise.

Permanent damage to hearing from prolonged or intense sound exposure, such as aircraft engines or cockpit noise. It is cumulative and irreversible, so hearing protection and limiting exposure are the only safeguards.

A framework describing human error as a mismatch at the interfaces between the software, hardware, environment, and liveware, with liveware at the centre. It is used to analyse where error arises in an aviation system.

An operational approach in which crews anticipate threats, trap or manage errors before they affect safety, and recover from any undesired aircraft state. It treats error as normal and focuses on detection and recovery.

The effective use of all available resources, including people, equipment, and information, to achieve safe flight. It covers communication, leadership, teamwork, workload management, and decision making.

An accurate, up-to-date understanding of the aircraft, the environment, and the crew's task, including how these will change. Loss of it is a common precursor to error and is countered by monitoring and cross-checking.

Planning and prioritising tasks so that demands stay within the crew's capacity, using delegation, automation, and shedding of non-essential work. It prevents task saturation and the errors that follow.

The willingness to state a concern clearly and persistently until it is acknowledged, while respecting others. It is a core CRM behaviour that prevents a junior crew member's valid observation from being ignored.

The perceived difference in power or experience between crew members. Too steep a gradient discourages challenge, while too flat a one causes confusion, so an appropriate balance supports safe challenge and clear command.

A rule restricting non-essential conversation and activity during critical phases of flight such as taxi, takeoff, approach, and landing. It protects attention and communication when workload and risk are highest.

The tendency to seek and interpret information that supports an existing belief while ignoring contrary evidence. In flight it can cause a crew to persist with a wrong diagnosis or plan despite warning signs.

The tendency to continue with an original plan despite changing conditions that call for a revised one. It contributes to pressing on into deteriorating weather or continuing an unstable approach.

The process of choosing a course of action by gathering information, assessing options, and committing to one. In aviation it is time-limited and should include a review point and a clear alternative.

The body's response to demands or threats, which can sharpen performance at moderate levels but degrade it when excessive or prolonged. Sources include workload, fatigue, noise, and interpersonal conflict.

A physiological state of reduced mental or physical capability caused by sleep loss, long duty periods, or circadian disruption. It impairs attention and reaction time in ways the person often underestimates.

The roughly 24-hour internal cycle that regulates sleepiness, alertness, and body temperature. Flying across time zones or at night can desynchronise it, producing low alertness during the early morning hours.

Reduced vigilance and monitoring that develops when automated systems perform reliably, so the operator stops checking them closely. It can leave the crew unprepared when the automation fails or behaves unexpectedly.

The tendency to over-trust automated information and accept it in preference to other evidence or one's own judgement. It can lead a crew to follow a faulty flight guidance or warning without independent verification.

A state in which the crew misunderstands which automation mode is active or what the aircraft will do next. It arises from complex mode logic and inadequate monitoring, and can produce unexpected flight path changes.

Vision outside the central field, which detects motion and dim light but not fine detail or colour. It is important for spotting traffic and for maintaining orientation, and degrades with fatigue and low oxygen.