PPL Human Performance and Limitations flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

SHELL model

A human-factors framework: Liveware (the human) at the centre interacts with Software (procedures, rules), Hardware (equipment), Environment and other Liveware; mismatches at these interfaces are where errors arise.

Hypemic hypoxia

Hypoxia caused by reduced oxygen-carrying capacity of the blood despite normal lung function, e.g. anaemia or carbon monoxide poisoning; treat with 100% oxygen and remove the cause.

Time of useful consciousness

The period after loss of oxygen supply during which a person can still act usefully; roughly 15-30 s at FL 400, 30-60 s at FL 350 and 2-5 min at FL 300, varying with activity and individual.

Boyle's law and barotrauma

At constant temperature, gas volume is inversely proportional to pressure. Trapped gas expands on ascent and contracts on descent, causing barotrauma in ears, sinuses and gut.

Valsalva manoeuvre

A gentle nose-pinch with a blow against the closed nose, used to equalise middle-ear pressure on descent; it raises intrathoracic pressure and can affect blood pressure and heart rhythm.

Nocturnal (scotopic) vision

Night vision uses rods, which are concentrated in the retinal periphery and are insensitive to colour; use off-centre viewing of about 10-15 degrees and allow about 30 minutes for dark adaptation.

Circadian rhythm

The roughly 24-hour internal clock entrained mainly by light; eastward travel (phase advance) is generally harder to adapt to than westward travel, and adaptation takes days.

Fatigue and sleep debt

Fatigue is a cumulative degradation of performance from insufficient or poor-quality sleep; sleep debt is not repaid by one long sleep, and fatigue impairs vigilance before the person notices.

Vigilance decrement

The decline in detection performance during prolonged, monotonous monitoring tasks, typically appearing within about 30 minutes; it is a normal attentional limit, not a motivation failure.

Working memory limit

Working memory holds only about 7 plus or minus 2 items for a few seconds; clearances and calculations must be written down or read back to avoid loss.

Yerkes-Dodson law

Performance improves with arousal up to an optimum and then declines; high stress narrows attention, increases errors of omission and reduces the ability to consider alternatives.

Inattentional blindness

Failure to perceive an unexpected but visible object while attention is engaged on another task; expectation and task focus determine what is actually seen.

Somatogravic illusion

Linear acceleration is misread as a change of attitude because otoliths cannot separate gravity from acceleration; take-off acceleration feels nose-up and deceleration feels nose-down.

The leans

A slow bank below the threshold of the semicircular canals is not perceived; the pilot feels level while banked and may correct in the wrong direction when returning to instruments.

Coriolis illusion

A tumbling sensation produced by moving the head during a sustained turn, when one canal is already adapted; avoid head movements during prolonged turns and trust the instruments.

Black-hole effect

On a dark approach with no ground reference, the absence of visual cues causes the pilot to fly a too-low approach; use instruments and glidepath guidance instead of visual judgement.

DECIDE model

A decision cycle: Detect the change, Estimate the need to react, Choose an outcome, Identify actions, Do the actions, Evaluate the results; it structures decisions under time pressure.

Confirmation bias

The tendency to seek and weight information that supports an existing hypothesis while ignoring contrary evidence; counter it by actively seeking disconfirming data.

Plan continuation bias

Continuing with an original plan despite accumulating evidence that it is no longer appropriate; countered by setting explicit decision gates before flight.

Slip versus mistake

A slip is a correct intention executed incorrectly (attention failure); a mistake is a wrong intention or plan (rule or knowledge failure); lapses are memory failures.

Automation complacency

Reduced monitoring of automated systems because they usually work; it leads to mode confusion and delayed detection of failures; verbalise what the automation is doing.

PACE model

A graded assertiveness tool: Probe, Alert, Challenge, Emergency; it escalates a safety concern when earlier, softer statements have not been acknowledged by the other crew member.

Authority gradient

The perceived difference in authority between crew members; too steep suppresses junior input, too flat causes indecision; the captain should invite challenge and state intent.

Read-back requirement

Repeating a clearance or instruction back to the sender to confirm correct reception; it closes the communication loop and traps errors in clearances, altitudes and frequencies.

Situational awareness levels

Three levels: perception of elements, comprehension of their meaning, and projection of future status; loss of SA precedes most undesired aircraft states.

Threat and Error Management

A framework in which threats (external events) and errors (crew actions) are anticipated; countermeasures are avoidance, trapping and recovery before an undesired aircraft state develops.

Swiss cheese model

Reason's model in which defences have holes; an accident occurs when holes in successive defences align; the aim is to strengthen defences rather than blame the last person.

Undesired aircraft state

A state such as an unstable approach, wrong runway or altitude deviation that results from an error or threat and increases risk; recognising and recovering from it is a core TEM skill.

Just culture

A reporting culture that distinguishes human error (console), at-risk behaviour (coach) and reckless behaviour (sanction), encouraging reporting while retaining accountability for reckless acts.

Safety Management System

An organisational system with four components: safety policy, safety risk management, safety assurance and safety promotion; it manages risk proactively rather than reacting to accidents.

LOSA

Line Operations Safety Audit: structured observation of normal flights to collect threat and error data; it is proactive and non-punitive, not an inspection of individual pilots.

Leading versus lagging indicators

Leading indicators (reporting rates, audit findings, exceedances) predict future safety performance; lagging indicators (accidents, incidents) measure outcomes after the fact.