Human Performance

Fatigue can impair attention, reaction time and judgment, including the ability to assess one's own performance. Use fitness-for-duty and fatigue-reporting procedures.

Without reliable visual references, the vestibular system can create misleading sensations of attitude or motion. A disciplined scan of reliable instruments helps prevent spatial disorientation.

A passive spot only helps if the pilot notices and correctly interprets its colour change. Workload, poor light or developing carbon monoxide impairment can defeat that visual check. NTSB investigations also note replacement-life and contamination limitations. A suitable active detector can attract attention through an audible or visual warning before the pilot happens to inspect a spot. This explains the NTSB’s recommendation for effective active alerting; it does not remove the need for correct installation, maintenance and the aircraft’s response procedure.

Scope: Especially relevant to enclosed-cabin general aviation aircraft with CO ingress potential.

Sources

• NTSB AIR-22-01 — Require Carbon Monoxide Detectors in Certain General Aviation Aircraft — Printed pp. 5–6 — passive spot detector limitations and effective active alerting; pp. 8–9 — Conclusions and Recommendations A-22-1/A-22-2. Accessed 2026-10-03.

The eye adapts to the light environment it is exposed to. Bright cockpit lighting and reflections can reduce useful contrast with a dark outside scene and interfere with dark adaptation. FAA night-flight guidance illustrates how outside features become less visible as interior lighting is increased. Set lighting to a level that permits reliable instrument and chart reading while preserving outside vision as far as practicable. The purpose is a workable balance; switching off essential lighting is not the objective.

Scope: General unaided night vision; use aircraft lighting procedures.

Sources

• FAA Helicopter Flying Handbook — Chapter 13: Night Operations — Printed pp. 13-2 and 13-4 — light discipline and Figure 13-1. Accessed 2026-10-03.

After a sustained turn, the vestibular system may no longer provide an accurate sensation of the ongoing rotation. A sudden head tilt can stimulate the semicircular canals in a different combination, producing a powerful false impression of simultaneous roll, pitch and yaw. This is the Coriolis illusion. Looking abruptly toward an overhead switch or down at a chart can be the trigger. Organize cockpit tasks to avoid unnecessary sudden head movements in turns and maintain attitude control by reliable instrument reference.

Scope: General vestibular physiology in flight.

Sources

• FAA AM-400-03/1 — Spatial Disorientation: Why You Shouldn’t Fly By the Seat of Your Pants — PDF p. 3 — The Coriolis Illusion; p. 4 — How to Prevent Spatial Disorientation. Accessed 2026-10-03.

Diving can leave excess dissolved nitrogen in body tissues. A subsequent reduction in ambient pressure can allow bubbles to form, creating decompression-sickness risk; oxygen availability is a different issue. Pressurization reduces exposure to low pressure but does not automatically reproduce sea-level conditions or remove the possibility of an aircraft decompression. The FAA’s recommended waiting guidance explicitly considers actual flight altitude, not only planned cabin altitude. Apply the relevant diving, aeromedical and operator guidance rather than treating a pressurized cabin as an exemption.

Scope: General physiology and FAA guidance distinction; no individualized dive-to-fly interval is supplied.

Sources

• FAA AIM — Medical Facts for Pilots — 8-1-2 d. Decompression Sickness After Scuba Diving. Accessed 2026-10-03.

During climb, expanding air in the middle ear can push the eustachian tube open and escape. During descent, pressure equalization requires air to enter through the tube, which must be opened periodically. Congestion from a cold or allergy can obstruct this process; the pressure difference can then help keep the tube closed. The result may be pain and impaired hearing. This explains why a comfortable climb does not demonstrate fitness for a trouble-free descent, and why medication alone is not a reliable solution.

Scope: General physiology; fitness decisions and treatment require appropriate aeromedical advice.

Sources

• FAA AIM — Medical Facts for Pilots — 8-1-2 b. Ear Block. Accessed 2026-10-03.

Circadian rhythm is the body’s internal biological clock, regulating sleep-wake cycles over approximately 24 hours. During long-haul operations that cross multiple time zones, pilots may be required to operate during the circadian low—typically between 2 a.m. and 6 a.m. body time—when alertness, cognitive performance, and reaction time are at their lowest. This misalignment can lead to increased fatigue, reduced situational awareness, and a higher risk of errors.

A prolonged coordinated turn can cease to feel like a turn as the vestibular system adapts. The pilot may notice altitude loss while mistakenly feeling wings-level. Pulling back without correcting the bank tightens the turn instead of providing the expected straight-flight recovery, and the descent can worsen. The trap is an incorrect mental picture of attitude. Recognize the bank using reliable instruments and apply the aircraft’s trained recovery technique; the apparent bodily sensation of level flight is not adequate evidence.

Scope: Recognition and mechanism only; recovery technique is aircraft- and training-specific.

Sources

• FAA AM-400-03/1 — Spatial Disorientation: Why You Shouldn’t Fly By the Seat of Your Pants — PDF p. 3 — The Graveyard Spiral. Accessed 2026-10-03.

The centre of the retina provides excellent daylight detail but is dominated by cones, which perform poorly in darkness. Rods outside that central region are more sensitive to dim light. Looking slightly off the object therefore places its image on a more useful part of the retina for night detection. FAA guidance recommends off-centre scanning and small eye movements rather than prolonged staring. It is a detection technique for dim outside objects, not a replacement for directly reading illuminated flight instruments.

Scope: Unaided human night vision; not night-vision-goggle operating guidance.

Sources

• FAA Helicopter Flying Handbook — Chapter 13: Night Operations — Printed p. 13-4 — Cones, Rods and Night Scanning; Figure 13-4. Accessed 2026-10-03.

The passenger’s symptoms are consistent with hyperventilation — breathing faster or deeper than required, which lowers the blood’s carbon dioxide (CO₂) level. Typical signs include dizziness, tingling around the mouth or in the fingers, chest discomfort, visual disturbance and anxiety.

ATPL theoretical-knowledge context

For an EASA ATPL examination, Subject 040 learning objective 37 lists the following measures to counteract hyperventilation: slow the breathing, close one nostril, speak aloud, or place a paper bag over the nose and mouth. Therefore, where a multiple-choice question specifically tests the EASA ATPL syllabus, the paper-bag answer may be the expected theoretical response.

Operational context

In an actual passenger event, these symptoms are not diagnostic of hyperventilation and may also occur with hypoxia or a cardiac, respiratory or neurological problem. Inform the cabin crew, reassure the passenger, encourage slow and controlled breathing, monitor the passenger, and obtain medical assistance as required. Do not substitute an examination mnemonic for the applicable onboard procedure.

Safety note: This answer explains ATPL theoretical knowledge and is not medical advice. Always follow the operator’s Operations Manual, company procedures and the instructions of qualified cabin crew or medical personnel. Current first-aid guidance may advise against paper-bag rebreathing because it can worsen an incorrectly diagnosed condition.

References: EASA Subject 040, learning objective 37; St John Ambulance — hyperventilation first-aid guidance.

Polarization can interact with instrument anti-glare filters and display materials, reducing or even eliminating the visibility of some indications. It can also accentuate patterns in laminated windscreens and reduce reflections that help reveal other aircraft. Thus, reducing glare is not the only criterion for cockpit eyewear. The FAA advises against polarized lenses for aviation use. Evaluate eyewear compatibility with the actual cockpit and its displays, including different viewing angles, and follow the operator’s applicable requirements.

Scope: FAA eyewear recommendation; effects depend on cockpit/display/lens combination.

Sources

• FAA — Sunglasses for Pilots (2024) — Polarization section and Before You Fly list. Accessed 2026-10-03.

A wider-than-usual runway, such as one 60 metres wide, can create the illusion that the aircraft is lower than it actually is, potentially leading to a higher-than-normal approach path.

The visual black hole effect is a hazardous illusion encountered during night approaches over featureless terrain (e.g. sea, desert, unlit terrain), where there are no peripheral visual cues between the aircraft and the runway.

What causes the illusion?

Pilots affected by this illusion tend to unconsciously fly a curved, low approach path, instead of maintaining a safe, constant-angle glidepath.

According to Kraft and Elworth's theory, this happens because the pilot tries to keep the visual angle to the runway constant (i.e. the angle between the eye and the runway appears unchanging).
This null angular change creates the illusion of a stable approach, but in reality, the aircraft is descending below the correct glidepath, increasing the risk of controlled flight into terrain (CFIT).

In the illustration, both the safe path and the curved path create the same visual angle (Θ), giving the false perception of being on the right glide.

How to prevent it:

• Avoid relying solely on visual cues, especially at night.
• Use instruments, ILS, or PAPI/VASI to monitor the correct glidepath.
• Follow stabilised approach procedures and cross-check descent rates and altitudes.

This illusion shows how the human visual system can be misled, especially in poor visual environments.