Section 9.2

Human Performance and Limitations

Vision, hearing, information processing, attention and perception, memory, claustrophobia and physical access.

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Main ideas

Vision is the dominant sense for inspection tasks but degrades in poor lighting, low contrast, glare and with age (presbyopia) — this is why visual inspection standards specify minimum illumination and viewing distance.
Hearing loss from unprotected exposure to engine run-ups and hangar noise is cumulative and irreversible — hearing protection is a human factors control, not just a comfort item.
Information processing follows input (senses) → central processing (attention, memory, decision) → output (action); a bottleneck or overload at any stage increases error probability.
Short-term (working) memory holds roughly 5–9 items for under a minute — this is why a technician who is interrupted mid-task frequently loses their place, and why written work cards exist instead of relying on memory.
Confined spaces (fuel tanks, wheel wells) can trigger claustrophobia and restrict physical access and dexterity, raising the chance of a rushed or incomplete inspection.
⚠ Exam trap: an interruption wipes working memory (~5–9 items) — write the number down; and expectation shapes perception, so a briefed inspector detects more.

Solved examples

A technician is asked to remember a 6-digit work order number while also being asked a question by a supervisor. They mis-key the work order afterwards. Why?
Working memory has limited capacity and decays quickly, especially when a competing task (answering the supervisor) interrupts rehearsal — the fix is to write the number down immediately rather than hold it in memory.

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