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Private pilot · ACS PA.I.H · lesson pack

Human Factors

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Why this one matters

Most accidents involve a human decision, not a broken airplane: flying impaired, tired or under pressure, disorientation in poor visibility, or a hazardous attitude overriding good judgment. This task is about knowing how your body and mind can fail you in the air, and the tools that catch it before it matters.

1 · Know these cold

  • •Check yourself before every flight with IMSAFE: Illness, Medication, Stress, Alcohol, Fatigue, Emotion (or Eating).(PHAK (FAA-H-8083-25C), Aeronautical Decision-Making)
  • •Hypoxia sneaks up: euphoria, headache, poor judgment. The cure is oxygen and descent.(PHAK (FAA-H-8083-25C), Aeromedical Factors)
  • •Spatial disorientation: your inner ear lies without outside references. Believe the instruments.(PHAK (FAA-H-8083-25C), Aeromedical Factors)
  • •Carbon monoxide from a heater leak causes headache and drowsiness: heat off, vents open, land.(PHAK (FAA-H-8083-25C), Aeromedical Factors)
  • •No flying within 8 hours of alcohol, under the influence, or at 0.04 or above; no drugs that affect your faculties.(14 CFR 91.17)
  • •The five hazardous attitudes (anti-authority, impulsivity, invulnerability, macho, resignation) each have an antidote you say to yourself.(PHAK (FAA-H-8083-25C), Aeronautical Decision-Making)
  • •Expectation and confirmation bias make you hear the clearance you expect and see what you want: read back and verify.(Risk Management Handbook (FAA-H-8083-2A))

2 · The lesson

Your body at altitude and in the cockpit
  • Hypoxia: not enough oxygen. Hypoxic (altitude), hypemic (blood can't carry it, e.g. carbon monoxide), stagnant (poor circulation) and histotoxic (cells can't use it, e.g. alcohol). Symptoms include euphoria, headache, blue lips and fingernails, and impaired judgment; they differ from person to person and come on insidiously, so you can't count on noticing them. Night vision degrades from about 5,000 feet; smoking, alcohol, fatigue, cold and some medications make it worse; impairment can start well below the 91.211 oxygen altitudes (crew above 12,500 for over 30 minutes, above 14,000 always; passengers provided above 15,000). For altitude hypoxia, use oxygen and descend. For carbon monoxide or a histotoxic cause, also remove the cause and get medical care: descending alone doesn't fix it.(PHAK (FAA-H-8083-25C), Aeromedical Factors; 14 CFR 91.211)
  • Hyperventilation (breathing too fast, often from stress) feels much like hypoxia: tingling, dizziness, lightheadedness. At altitude or on oxygen, treat it as hypoxia first: check the oxygen equipment and flow, use oxygen, descend. Only once hypoxia is ruled out, slow your breathing, talk out loud, or breathe into a paper bag; bag-breathing a hypoxic pilot makes it worse.(PHAK (FAA-H-8083-25C), Aeromedical Factors; AIM 8-1-2, 8-1-3)
  • Carbon monoxide (from an exhaust leak into the cabin heat): headache, drowsiness, dizziness. Turn the heat off, open the fresh-air vents and windows, use oxygen if available, land as soon as possible, get medical attention, and have the airplane inspected before it flies again. A CO detector is recommended, not required, and spot detectors are unreliable: knowing the symptoms and these actions is the real defense.(PHAK (FAA-H-8083-25C), Aeromedical Factors; AIM 8-1-4)
  • Ear and sinus blocks: equalize early and often in a descent with a gentle Valsalva (pinch your nostrils and blow slowly; never force it, which can injure the eardrum). If a block develops, climb to relieve it, equalize gently, then descend more slowly. Sinus blocks can happen in a climb or a descent. Don't fly with a cold or congestion.(PHAK (FAA-H-8083-25C), Aeromedical Factors; AIM 8-1-4)
  • Spatial disorientation: without outside references, the inner ear gives false signals. The vestibular illusions: the leans, Coriolis (from moving your head in a turn), the graveyard spiral, the graveyard spin, somatogravic (acceleration feels like pitching up), inversion, and the elevator illusion. Fly the attitude indicator despite what you feel, keep head movements small in turns, avoid abrupt maneuvers, don't continue VFR into IMC, and hand off to another pilot if one is aboard. In a graveyard spiral, reduce power and level the wings before easing the nose up; pulling back alone tightens it.(PHAK (FAA-H-8083-25C), Aeromedical Factors; AIM 8-1-5)
  • Motion sickness: open vents, focus outside, minimize head movement. Some motion-sickness medications cause drowsiness.(PHAK (FAA-H-8083-25C), Aeromedical Factors)
  • Carbon monoxide is odorless; a heater exhaust leak causes headache, drowsiness and confusion. Carry a CO detector.(PHAK (FAA-H-8083-25C), Aeromedical Factors)
  • Stress can be acute (a sudden emergency) or chronic (life pressures building up); chronic stress makes you unfit to fly. Fatigue, acute or chronic, slows reactions and judgment: only sleep cures it, and caffeine only masks it.(PHAK (FAA-H-8083-25C), Aeromedical Factors)
  • Dehydration: thirst comes late; drink before and during flight, especially in heat and at altitude, or expect headache, fatigue and poor judgment. Nutrition: skipped meals and low blood sugar bring weakness and poor concentration. Hypothermia: a lowered core temperature brings shivering, confusion, poor coordination and judgment; dress for the terrain and a possible forced landing, get warm and get medical care.(PHAK (FAA-H-8083-25C), Aeromedical Factors)
  • Landing illusions: a narrow or upsloping runway makes you feel high (you'll tend to fly a low approach); a wide or downsloping runway makes you feel low; featureless terrain or water at night ("black hole") makes you feel high too. Rain on the windshield and haze make you feel higher and farther away; entering fog can feel like pitching up; bright runway lights make the runway seem closer. Autokinesis: a stationary light stared at in the dark seems to move. A sloping cloud deck or terrain can create a false horizon. Counter them with the glidepath indicators, an altimeter cross-check, and not staring at one light.(PHAK (FAA-H-8083-25C), Aeromedical Factors; AIM 8-1-5)
  • Scuba diving: wait at least 12 hours after diving that didn't need decompression stops before flying up to 8,000 feet, and at least 24 hours before higher flights or after decompression-stop diving.(AIM chapter 8, Medical Facts for Pilots)
Alcohol, drugs and medication
  • No acting as a crewmember within 8 hours of drinking alcohol, while under the influence, or with a blood alcohol concentration of 0.04 or more.(14 CFR 91.17(a))
  • Except in an emergency, you may not carry a passenger who appears intoxicated or under the influence of drugs (a medical patient under proper care is the exception).(14 CFR 91.17(b))
  • No acting as a crewmember while using any drug that affects your faculties contrary to safety.(14 CFR 91.17(a))
  • Alcohol impairs judgment and makes you more susceptible to hypoxia and disorientation, and its effects can last well beyond 8 hours. Many pilots use 12 or 24 hours.(PHAK (FAA-H-8083-25C), Aeromedical Factors)
  • Over-the-counter drugs (antihistamines, cold and sleep medicines) can cause drowsiness. Don't fly while taking a medication that would keep you from meeting the medical standards; ask an AME when unsure.(14 CFR 61.53; PHAK (FAA-H-8083-25C), Aeromedical Factors)
Making decisions
  • Single-pilot resource management means using everything available: ATC, Flight Service, passengers, automation and checklists.(Risk Management Handbook (FAA-H-8083-2A))
  • Tools: IMSAFE (yourself), PAVE (Pilot, Aircraft, enVironment, External pressures) for the flight, and a structured decision model. DECIDE is the classic one: Detect that something changed, Estimate the need to respond, Choose a desired outcome, Identify actions that get you there, Do it, and Evaluate the result. It works on the ground and in the air.(PHAK (FAA-H-8083-25C), Aeronautical Decision-Making)
  • Personal minimums as a method: write down limits more conservative than the legal ones (wind and crosswind, ceiling, visibility, rest, recent experience) before you need them, then use IMSAFE against them as a go/no-go gate before every flight.(PHAK (FAA-H-8083-25C), Aeronautical Decision-Making)
  • Hazardous attitudes and their antidotes: anti-authority ("Follow the rules. They are usually right."), impulsivity ("Not so fast. Think first."), invulnerability ("It could happen to me."), macho ("Taking chances is foolish."), resignation ("I'm not helpless. I can make a difference.").(PHAK (FAA-H-8083-25C), Aeronautical Decision-Making)
Attention and bias
  • Distractions break the chain of tasks. Prioritize: aviate, navigate, communicate.(Risk Management Handbook (FAA-H-8083-2A))
  • Loss of situational awareness often starts with fixation on one problem. Step back and fly the airplane.(Risk Management Handbook (FAA-H-8083-2A))
  • Expectation bias: you hear the clearance you expected. Confirmation bias: you favor information that supports what you've already decided. Read back clearances fully and look for evidence that you're wrong.(Risk Management Handbook (FAA-H-8083-2A))

Want it all on one page, with scenarios? Read the full lesson.

3 · Say it out loud

Answer each one out loud, then check yourself and mark how it went.

  1. Remember Recall it

    “What does IMSAFE stand for?”

  2. Understand Explain why

    “Why is hypoxia so dangerous even though it isn't painful?”

  3. Apply Use it on a flight

    “You're tired after a long workday, but the weather is perfect and you promised a friend a flight tonight. What do you do?”

4 · Common mistakes

  • Naming a hazardous attitude without saying what you'd do.

    Recognizing it is only the start.

    Instead: Say the antidote and the action it leads to.

  • Treating "8 hours bottle to throttle" as enough.

    Effects can last well beyond 8 hours, and 0.04 or impairment still applies.

    Instead: Use a longer personal limit and judge how you feel.

  • Trusting your body over the instruments in low visibility.

    The inner ear gives false signals without outside references.

    Instead: Fly the attitude indicator and cross-check.

5 · Quick check

Answer, then reveal. Flag anything you want to see again.

  1. 1. What are the four types of hypoxia?

  2. 2. What is the antidote to the impulsivity attitude?

  3. 3. How long must you wait after drinking alcohol before flying?

  4. 4. Which illusion does an upsloping runway create?

  5. Scenario5. After a recreational dive without decompression stops, how long should you wait before flying at 6,500 feet?

  6. 6. What is expectation bias?

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Connect it

One situation that runs across this lesson and its neighbors in the same ACS area. Decide first, then check.

Connect it · Preflight Preparation

A July afternoon. You plan a 90 NM trip from a 2,800-foot runway at 1,500 feet elevation; it's 33 °C. The destination TAF has a TEMPO for thunderstorms starting about when you'd arrive.

How do the weather, the airplane's performance and your fuel plan change one another, and what do you decide? Decide, then see the worked answer

Work the density altitude first. Standard temperature at 1,500 feet is about 12 °C, so 33 °C is about ISA +21 °C and the density altitude is roughly 4,000 feet (more if the pressure is low). Enter the POH takeoff and climb charts at the actual pressure altitude and temperature, never the field elevation, and compare the ground roll, the distance over a 50-foot obstacle and the climb with the 2,800 feet and the obstacles, with a margin. If it's tight, cut payload and baggage first. Never cut fuel below trip fuel plus fuel to divert to an alternate plus the 91.151(a)(1) day VFR reserve of 30 minutes at normal cruise. After any load change, recompute the weight and balance and the CG, and check the landing distance at the destination too. The TEMPO puts thunderstorms over the destination at your arrival. Don't plan to beat the TEMPO window or to divert closely around cells: avoid thunderstorms with severe or intense radar echoes by at least 20 miles, never take off or land in the face of an approaching thunderstorm, and wait storms out on the ground. With thin performance margins and storms at the far end, the better answer is the cooler, calmer morning.

PHAK (FAA-H-8083-25C), Aircraft Performance and Weather Theory; AC 00-24C, Thunderstorms; 14 CFR 91.103, 91.151

Brings together: Weather Information · Cross-Country Flight Planning · Performance and Limitations

Teaching this? The instructor lesson plan →

Study aid, not FAA guidance. Sources: Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C); Risk Management Handbook (FAA-H-8083-2A); AIM; 14 CFR 61.53, 91.17. Checked against current sources 2026-11-12.