PRIVATE PILOT 10 / LEARN · EXPLORE · CHECK
Aeromedical Factors
Recognize changes in how you feel, see, and think—and take action before they become a flight emergency.
Your learning goals
- Recognize common aeromedical hazards and connect symptoms with practical action.
- Explain why oxygen, breathing, vision, and the inner ear can mislead a pilot.
- Assess fitness, medication effects, alcohol restrictions, and diving history before flight.
- Choose prevention, diversion, or landing instead of pressing on while impaired.
Start with the pilot
Supporting ACS Area I.H, this lesson focuses on physiology and fitness decisions. A valid medical qualification does not guarantee fitness today. Use IMSAFE: Illness, Medication, Stress, Alcohol, Fatigue, and Emotion. Also check food, hydration, and recent diving. If a concern could affect safe flying, resolve it or postpone.
Stress can narrow attention and make simple tasks harder. Poor sleep, hunger, heat, and pressure to arrive can combine. Reduce demands, share appropriate tasks with a qualified pilot, and keep a realistic cancellation option. Reassess in flight: missed calls, unusual irritability, or repeated mistakes are reasons to change the plan.
Symptoms can overlap. Fly the airplane, address likely hazards promptly, ask ATC for help as needed, and land when safe continuation is in doubt. Do not spend critical time trying to prove one diagnosis.
PHAK Chapter 17: health and stress · AIM 8-1-1: fitness for flight
Hypoxia: too little oxygen reaching the tissues
Hypoxia can quietly impair judgment, coordination, and vision. You may notice headache, dizziness, drowsiness, unusual confidence or euphoria, or difficulty doing familiar tasks. The person affected may not recognize the problem.
- Hypoxic: not enough oxygen available to enter the blood, as when oxygen partial pressure decreases at altitude.
- Hypemic: reduced oxygen transport by the blood, as with carbon monoxide exposure or anemia.
- Stagnant: inadequate circulation to the tissues.
- Histotoxic: cells cannot use the delivered oxygen effectively, as with certain toxic substances.
Act: use supplemental oxygen promptly when available and descend to a safe lower altitude, respecting terrain and weather. Check oxygen delivery and follow the equipment/aircraft procedures. Ask for help and land if symptoms persist or safe operation is doubtful. Fitness does not make someone immune.
Prevent: plan altitude and oxygen before flight, know the system, and monitor yourself and passengers. Legal thresholds are not personal protection guarantees. For U.S. civil aircraft under §91.211(a), required minimum flight crew must use oxygen for the portion beyond 30 minutes at cabin pressure altitudes above 12,500 through 14,000 ft MSL; above 14,000 ft, they must use it throughout. Above 15,000 ft, each occupant must be provided oxygen. These are cabin pressure altitudes. See supplemental oxygen for the detailed rule.
FAA guidance encourages oxygen above 10,000 ft by day and 5,000 ft at night. These recommendations are lower than the legal crew-use thresholds because performance and night vision can suffer earlier.
PHAK Chapter 17: hypoxia · 14 CFR §91.211(a) · AIM 8-1-2: altitude effects
Hyperventilation: breathing too much
Anxiety or stress can cause excessively rapid or deep breathing, reducing carbon dioxide in the blood. Tingling, lightheadedness, dizziness, muscle tightness, and a feeling of breathlessness can follow, which may increase anxiety further.
Act: deliberately return breathing rate and depth to normal; talking calmly can help. Reduce workload and reassure an affected passenger. Do not assume dizziness is only anxiety: hypoxia and hyperventilation can occur together. If using oxygen, ensure delivery first; AIM guidance calls for 100 percent oxygen if the system supports it and checking system function before focusing on breathing. Address possible altitude hypoxia as taught above.
Prevent: prepare for workload, use calm communication, and notice changes in breathing early. Worsening symptoms or loss of consciousness is an emergency, not a remedy to wait for; obtain help and land.
Carbon monoxide: suspect the cabin environment
Carbon monoxide (CO) is odorless and colorless. It interferes with the blood’s ability to carry oxygen. An exhaust leak, including a leak associated with an exhaust-based cabin heater, can expose everyone aboard. Headache, nausea, dizziness, drowsiness, weakness, or a CO detector alert should prompt action. Exhaust odor is a clue; lack of odor does not rule out CO.
Act: follow the aircraft checklist, turn off the cabin heater, open fresh-air vents, use supplemental oxygen if available, and land as soon as practicable. Tell ATC if you need assistance; severe impairment warrants an emergency declaration. Seek medical attention for suspected exposure, especially severe or continuing symptoms. A descent alone does not remove the source.
Prevent: maintain the exhaust/heating system, check the CO detector according to its instructions, and brief passengers to report symptoms. Do not continue simply because ventilation makes you feel better.
Spatial disorientation: trust reliable references
Your inner ear senses changes in motion; it cannot reliably tell attitude in all flight conditions. In haze, cloud, darkness, or over featureless terrain, the airplane may feel level when it is banked.
- The leans: correcting a slowly developed bank can feel like banking the other way.
- Coriolis illusion: a sudden head movement during a prolonged turn can produce a tumbling sensation.
- Somatogravic illusion: acceleration can feel like pitching up, tempting an unsafe push forward.
- Graveyard spiral: a banked descent feels wings-level; pulling back without correcting bank tightens the spiral.
Act: use a reliable external horizon when available; if it is lost, cross-check and trust the flight instruments and use your instrument training to maintain control. Avoid abrupt head movements and control inputs. Request ATC assistance promptly and follow a trained, terrain-aware plan to regain visual conditions. Do not maneuver by bodily sensation.
Prevent: stay out of deteriorating visibility, avoid routes or night conditions beyond your ability, and practice instrument reference with an instructor. An instrument display does not make an unqualified VFR pilot ready to continue in cloud.
Vision, night adaptation, and misleading approaches
Allow about 30 minutes for full dark adaptation. Bright lights can rapidly degrade it; dim cockpit/EFB lighting enough to preserve outside vision while keeping instruments readable. Use systematic scanning and off-center viewing for faint objects at night. Reduced oxygen, fatigue, and glare can make seeing harder.
A narrower-than-usual or upsloping runway can make you feel too high and tempt a low approach. A dark, featureless approach area—the black-hole effect—also removes useful height cues. Autokinesis makes a stationary light appear to move if stared at; keep scanning and cross-check other references.
Act: anticipate illusions from the airport briefing, cross-check altitude and a suitable visual glidepath indicator when available, and maintain a stabilized approach. Go around if the approach becomes unstable or the picture cannot be reconciled. Do not chase a visual impression with large corrections.
PHAK Chapter 17: vision and optical illusions · AIM 8-1-5 and 8-1-6
Motion sickness, ears, and sinuses
Motion sickness: conflicting visual and inner-ear information can cause nausea, sweating, pallor, dizziness, or vomiting. Look toward a stable distant horizon when available, use fresh air, avoid unnecessary head movement, and reduce maneuvering. Tell your instructor or other pilot early; shorten the flight or land if needed. Shorter, smoother lessons can help prevent recurrence. Do not self-medicate with potentially sedating motion-sickness remedies before flying.
Ear or sinus block: pressure changes with altitude require trapped air spaces to equalize. Congestion can prevent this, producing pain or reduced hearing, especially on descent. Avoid flying with an upper respiratory infection or significant congestion. Swallowing or yawning may help ear equalization; do not force a painful descent. Level off when safe, coordinate as needed, and seek medical advice if symptoms persist. A decongestant is not a guarantee against a block.
PHAK Chapter 17: motion sickness and ear/sinus problems · AIM 8-1-2
Fatigue, dehydration, food, and temperature
Fatigue slows reactions and weakens judgment. Repeated errors, poor concentration, and irritability may appear before you feel sleepy. Plan adequate sleep and breaks; postpone when unfit. If fatigue develops aloft, reduce workload and land at a suitable airport. Caffeine does not replace sleep or make a tired pilot fit.
Dehydration can cause headache, fatigue, dizziness, and reduced concentration. Hot cockpits and long flights increase risk. Drink water regularly, carry enough for the trip, and plan breaks rather than avoiding fluids to avoid bathroom stops. Eat regularly; hunger adds distraction and can impair performance. If symptoms develop, cool the cabin, hydrate as appropriate, and land if performance is affected. Severe confusion or collapse requires urgent medical help.
Cold exposure can impair dexterity and thinking; shivering or unusual clumsiness are warning signs. Wear suitable layers and carry survival supplies for the terrain and season. Warm up and end the exposure; do not trade ventilation for continued suspected CO exposure.
PHAK Chapter 17: fatigue, dehydration, and heatstroke · FAA: Dehydration and the Pilot · FAA: Hypothermia and Hyperthermia
Alcohol, drugs, and medication
§91.17 prohibits acting or attempting to act as a crewmember within 8 hours after drinking alcohol, while under its influence, while using a drug that affects faculties contrary to safety, or with an alcohol concentration of 0.04 or greater in a blood or breath specimen as defined in the rule. These are separate prohibitions: eight hours elapsed and a value below 0.04 do not establish fitness. A hangover can still impair judgment.
Prescription and over-the-counter products can cause sedation, slowed reactions, blurred vision, or other impairment. The illness being treated can matter as much as the drug, and combinations may worsen effects. Do not use alcohol or a stimulant to manage flight stress or fatigue.
Prevent: discuss the exact drug, dose, condition, side effects, and any required waiting period with an aviation medical examiner and your treating clinician before flying. Do not try a new medication in flight or assume a universal “five dosing intervals” rule clears every drug. Delay flight until both the condition and treatment are compatible with safe operation and applicable FAA guidance.
14 CFR §91.17 · FAA: Pharmaceuticals · PHAK Chapter 17: alcohol and drugs
Scuba diving and reduced pressure
Diving can leave excess nitrogen dissolved in the body. The lower pressure associated with flight can allow bubbles to form, causing decompression sickness. This affects passengers as well as pilots; a pressurized airplane is not an automatic exemption.
AIM 8-1-2 recommends waiting at least 12 hours after a dive that did not require decompression stops before flight up to 8,000 ft, and at least 24 hours after a dive requiring decompression stops. Before flight above 8,000 ft, wait at least 24 hours after any scuba dive. The PHAK specifies actual flight altitude above MSL for this guidance, not an assumption based on cabin altitude. These are minimum recommendations, not a guarantee for every dive or person; follow more conservative diving/medical guidance when applicable.
Prevent: ask about diving while planning the trip, not just at boarding. If timing or the dive profile is uncertain, postpone and obtain qualified advice. Joint pain, unusual neurological symptoms, or breathing difficulty after diving and ascent can be serious. Use oxygen if available, descend safely, land, and obtain urgent medical care; do not continue because symptoms improve.
AIM 8-1-2(d): decompression sickness after scuba diving · PHAK Chapter 17: altitude-induced decompression sickness
FLIGHT SCENARIO
What would change your plan?
During a cold-weather flight with the cabin heater on, both you and a passenger develop a headache and feel unusually sleepy. The passenger says it is probably fatigue and wants to continue. What would you do? After landing, you also learn that tomorrow’s passenger plans a scuba dive tonight.
- NoticeWhat does this situation require?
- VerifyWhat evidence is still missing?
- DecideWhat keeps an option open?
Compare your reasoning
Shared symptoms with the heater on suggest a cabin hazard such as carbon monoxide, even without an odor. Fly the airplane, follow the checklist, shut off the heater, ventilate, use oxygen if available, request help as needed, and land as soon as practicable. Seek medical attention for suspected exposure. For tomorrow, verify the dive profile and elapsed time against FAA waiting guidance and any more conservative advice; postpone when uncertain. Prevention and early action preserve options.
SUMMARY
Recognize impairment early and reduce the risk immediately.
Shared symptoms with the heater on suggest a cabin hazard such as carbon monoxide, even without an odor. Fly the airplane, follow the checklist, shut off the heater, ventilate, use oxygen if available, request help as needed, and land as soon as practicable. Seek medical attention for suspected exposure. For tomorrow, verify the dive profile and elapsed time against FAA waiting guidance and any more conservative advice; postpone when uncertain. Prevention and early action preserve options.
Before moving on, explain the decision in your own words: what would you verify, and what would make you change the plan?
PRACTICE
Flashcards and knowledge check
Six flashcards, then five questions with explanations.
Enable JavaScript for flashcards and the knowledge check. The lesson and scenario remain available without it.
Sources & lesson notes
Sources & lesson notes
- FAA PHAK, Chapter 17 — Aeromedical FactorsPhysiology, recognition, prevention, corrective actions, vision, and diving.
- FAA AIM, Chapter 8 Section 1 — Medical Facts for Pilots8-1-1 through 8-1-6: fitness, altitude, diving, breathing, CO, illusions, and vision.
- 14 CFR §91.17 — Alcohol or drugsIndependent time, influence, drug-effect, and concentration prohibitions.
- 14 CFR §91.211 — Supplemental oxygenCabin pressure altitude thresholds; required crew use and occupant provision.
- FAA — PharmaceuticalsIndividual medication/condition evaluation with an AME.
- FAA — Dehydration and the PilotRecognition and prevention of dehydration.
- FAA — A Pilot’s Guide to Hypothermia and HyperthermiaTemperature, hydration, impairment, and prevention.
- FAA-S-ACS-6C — Private Pilot Airplane ACSArea I, Task H, printed p. 8. This lesson supports physiology and fitness; it is not complete ADM/CRM or medical-certification instruction.
For U.S. private-pilot airplane study. Official sources checked September 29, 2026; eCFR text current through September 25, 2026. The supplied VFR Nav Log Explained and Aeromedical PDFs informed topics and terminology only; FAA guidance and regulations govern the explanations. All numerical examples are illustrative, not aircraft performance data. Use current information, the actual AFM/POH, and appropriate flight instruction.